Moirésuperlattices,arising from the controlled twisting of van der Waals homostructures at specific angles,have emerged as a promising platform for quantum emission applications.Concurrently,the manipulation of s...Moirésuperlattices,arising from the controlled twisting of van der Waals homostructures at specific angles,have emerged as a promising platform for quantum emission applications.Concurrently,the manipulation of strain provides a versatile strategy to finely adjust electronic band structures,enhance exciton luminescence efficiency,and establish a robust foundation for two-dimensional quantum light sources.However,the intricate interplay between strain and moirépotential remains partially unexplored.Here,we introduce a meticulously designed fusion of strain engineering and the twisted 2L-WSe_(2)/2L-WSe_(2) homobilayers,resulting in the precise localization of moiréexcitons.Employing low-temperature photoluminescence spectroscopy,we unveil the emergence of highly localized moiré-enhanced emission,characterized by the presence of multiple distinct emission lines.Furthermore,our investigation demonstrates the effective regulation of moirépotential depths through strain engineering,with the potential depths of strained and unstrained regions differing by 91%.By combining both experimental and theoretical approaches,our study elucidates the complex relationship between strain and moirépotential,thereby opening avenues for generating strain-induced moiréexciton single-photon sources.展开更多
The formation of moirésuperlattices in twisted van der Waals(vdW)homostructures provides a versatile platform for designing the electronic band structure of two-dimensional(2D)materials.In graphene and transition...The formation of moirésuperlattices in twisted van der Waals(vdW)homostructures provides a versatile platform for designing the electronic band structure of two-dimensional(2D)materials.In graphene and transition metal dichalcogenides(TMDs)moirésystems,twist angle has been shown to be a key parameter for regulating the moirésuperlattice.However,the effect of the modulation of the twist angle on moirépotential and interlayer coupling has not been the subject of experimental investigation.Here,we report the observation of the modulation of moirépotential and intralayer excitons in the WS_(2)/WS_(2)homostructure.By accurately adjusting the torsion angle of the homobilayers,the depth of the moirépotential can be modulated.The confinement effect of the moirépotential on the intralayer excitons was further demonstrated by the changing of temperature and valley polarization.Furthermore,we show that a detection of atomic reconstructions by the low-frequency Raman mapping to map out inhomogeneities in moirélattices on a large scale,which endows the uniformity of interlayer coupling.Our results provide insights for an in-depth understanding of the behaviors of moiréexcitons in the twisted van der Waals homostructure,and promote the study of electrical engineering and topological photonics.展开更多
Exploiting the valley degrees of freedom as information carriers provides new opportunities for the development of valleytronics.Monolayer transition metal dichalcogenides(TMDs)with broken space-inversion symmetry exh...Exploiting the valley degrees of freedom as information carriers provides new opportunities for the development of valleytronics.Monolayer transition metal dichalcogenides(TMDs)with broken space-inversion symmetry exhibit emerging valley pseudospins,making them ideal platforms for studying valley electronics.However,intervalley scattering of different energy valleys limits the achievable degree of valley polarization.Here,we constructed WSe_(2)/yttrium iron garnet(YIG)heterostructures and demonstrated that the interfacial magnetic exchange effect on the YIG magnetic substrate can enhance valley polarization by up to 63%,significantly higher than that of a monolayer WSe_(2)on SiO_(2)/Si(11%).Additionally,multiple sharp exciton peaks appear in the WSe_(2)/YIG heterostructures due to the strong magnetic proximity effect at the magnetic-substrate interface that enhances exciton emission efficiency.Moreover,under the effect of external magnetic field,the magnetic direction of the magnetic substrate enhances valley polarization,further demonstrating that the magnetic proximity effect regulates valley polarization.Our results provide a new way to regulate valley polarization and demonstrate the promising application of magnetic heterojunctions in magneto-optoelectronics.展开更多
The stacking of twisted two-dimensional(2D)layered materials has led to the creation of moirésuperlattices,which have become a new platform for the study of quantum optics.The strong coupling of moirésuperla...The stacking of twisted two-dimensional(2D)layered materials has led to the creation of moirésuperlattices,which have become a new platform for the study of quantum optics.The strong coupling of moirésuperlattices can result in flat minibands that boost electronic interactions and generate interesting strongly correlated states,including unconventional superconductivity,Mott insulating states,and moiréexcitons.However,the impact of adjusting and localizing moiréexcitons in Van der Waals heterostructures has yet to be explored experimentally.Here,we present experimental evidence of the localization-enhanced moiréexcitons in the twisted WSe_(2)/WS_(2)/WSe_(2)heterotrilayer with type-II band alignments.At low temperatures,we observed multiple excitons splitting in the twisted WSe_(2)/WS_(2)/WSe_(2)heterotrilayer,which is manifested as multiple sharp emission lines,in stark contrast to the moiréexcitonic behavior of the twisted WSe_(2)/WS_(2)heterobilayer(which has a linewidth 4 times wider).This is due to the enhancement of the two moirépotentials in the twisted heterotrilayer,enabling highly localized moiréexcitons at the interface.The confinement effect of moirépotential on moiréexcitons is further demonstrated by changes in temperature,laser power,and valley polarization.Our findings offer a new approach for localizing moiréexcitons in twist-angle heterostructures,which has the potential for the development of coherent quantum light emitters.展开更多
Recently,the discovery of a variety of moiré-related properties in the twisted vertical stacking of two different monolayers has attracted considerable attention.The introduction of small twist angles in transiti...Recently,the discovery of a variety of moiré-related properties in the twisted vertical stacking of two different monolayers has attracted considerable attention.The introduction of small twist angles in transition metal dichalcogenide(TMD)heterostructures leads to the emergence of moirépotentials,which provide a fascinating platform for the study of strong interactions of electrons.While there has been extensive research on moiréexcitons in twisted bilayer superlattices,the capture and study of moiréexcitons in homostructure superlattices with layer-coupling effects remain elusive.Here,we present the observation of moiréexcitons in the twisted 1L-WSe_(2)/1L-WSe_(2)and 1L-WSe_(2)/2L-WSe_(2)homostructures with various layer-coupling interactions.The results reveal that the moirépotential increases(~260%)as the number of underlying layers decreases,indicating the effect of layer coupling on the modulation of the moirépotential.The effects of the temperature and laser power dependence as well as valley polarization on moiréexcitons were further demonstrated,and the crucial spectral features observed were explained.Our findings pave the way for exploring quantum phenomena and related applications of quantum information.展开更多
Moirésuperlattices in van der Waals structures have emerged as a powerful platform for studying the novel quantum properties of two-dimensional materials.The periodic moirépatterns generated by these structu...Moirésuperlattices in van der Waals structures have emerged as a powerful platform for studying the novel quantum properties of two-dimensional materials.The periodic moirépatterns generated by these structures lead to the formation of flat mini-bands,which alter the electronic energy bands of the material.The resulting flat electronic bands can greatly enhance strong correlative interactions between electrons,leading to the emergence of exotic quantum phenomena,including moiréphonons and moiréexcitons.While extensive research has been conducted on the exotic quantum phenomena in twisted bilayers of transition metal dichalcogenides(TMDs),and the regulatory effect of stacked layers on moiréexcitons remains unexplored.In this study,we report the fabrication of a twisted WSe_(2)/WSe_(2)/WSe_(2) homotrilayer with two twist angles and investigate the influence of stacked layers on moiréexcitons.Our experiments reveal multiple moiréexciton splitting peaks in the twisted trilayer,with moirépotential depths of 78 and 112 meV in the bilayer and trilayer homostructures,respectively.We also observed the splitting of the moiréexcitons at 90 K,indicating the presence of a deeper moirépotential in the twisted trilayer.Moreover,we demonstrate that stacked layers can tune the moiréexcitons by manipulating temperature,laser power,and magnetic field.Our results provide a new physical model for studying moirésuperlattices and their quantum properties,which could potentially pave the way for the development of quantum optoelectronics.展开更多
Recent advances in twisted van der Waals heterostructure superlattices have emerged as a powerful and attractive platform for exploring novel condensed matter physics due to the interplay between the moirépotenti...Recent advances in twisted van der Waals heterostructure superlattices have emerged as a powerful and attractive platform for exploring novel condensed matter physics due to the interplay between the moirépotential and Coulomb interactions.The moirésuperlattices act as a periodic confinement potential in space to capture interlayer excitons(IXs),resulting in moiréexciton arrays,which provide opportunities for quantum emitters and many-body physics.The observation of moiréIXs in twisted transition-metal dichalcogenide(TMD)heterostructures has recently been widely reported.However,the capture and study of the moiréintralayer excitons based on TMD twisted homobilayer(T-HB)remain elusive.Here,we report the observation of moiréintralayer excitons in a WSe_(2)/WSe_(2) T-HB with a small twist angle by measuring PL spectrum.The multiple split peaks with an energy range of 1.55-1.73 eV are different from that of the monolayer WSe_(2) exciton peaks.The split peaks were caused by the trapping of intralayer excitons via the moirépotential.The confinement effect of the moirépotential on the moiréintralayer excitons was further demonstrated by the changing of temperature,laser power,and valley polarization.Our findings provide a new avenue for exploring new correlated quantum phenomena and their applications.展开更多
Van der Waals heterostructures have recently emerged,in which two distinct transitional metal dichalcogenide(TMD)monolayers are stacked vertically to generate interlayer excitons(IXs),offing new opportunites for the d...Van der Waals heterostructures have recently emerged,in which two distinct transitional metal dichalcogenide(TMD)monolayers are stacked vertically to generate interlayer excitons(IXs),offing new opportunites for the design of optoelectronic devices.However,the bilayer heterostructure with type-II band alignment can only produce low quantum yield.Here,we present the observation of interlayer neutral excitons and trions in the MoSe_(2)/MoS_(2)/MoSe_(2)trilayer heterostructure(Tri-HS).In comparison to the 8 K bilayer heterostructure,the addition of a MoSe_(2)layer to the Tri-HS can significantly increase the quantum yield of IXs.It is believed the two symmetrical type-II band alignments formed in the Tri-HS could effectively promote the IX radiation recombination.By analyzing the photoluminescence(PL)spectrum of the IXs at cryogenic temperature and the power dependence,the existence of the interlayer trions was confirmed.Our results provide a promising platform for the development of more efficient optoelectronic devices and the investigation of new physical properties of TMDs.展开更多
Moirésuperlattices are formed by a lattice mismatch or twist angle in two-dimensional materials,which can generate periodical moirépotentials leading to strong changes in the band structure,resulting in new ...Moirésuperlattices are formed by a lattice mismatch or twist angle in two-dimensional materials,which can generate periodical moirépotentials leading to strong changes in the band structure,resulting in new quantum phenomena.However,the experimental engineering of in-situ deformation of moiréheterostructures remains deficient.Here,we demonstrate a dynamic local deformation of the twisted heterostructures using a diamond anvil cell(DAC),enabling in-situ dynamic modulation of moirépotential in twisted WS_(2)–WSe_(2)heterostructures at room temperature.Deformation of the twisted heterostructure increases the moirépotential,causing a red shift of the moiréexciton resonance,and observed the red shift of the intralayer exciton resonance up to 16.3 meV(less than 1.1 GPa).The blue shift of the interlayer excitons of twisted WS_(2)–WSe_(2)heterostructures shows an evident transition of the pressure sensitive exciton,induced by the dominant effect of modifying the band structure on optical properties.Combined with the spectral changes of pressurized Raman,which further demonstrated that the DAC can efficiently regulate the interlayer coupling.Our results offer an effective strategy for in-situ dynamic modulation of moirépotential,providing a promising platform for the development of novel quantum devices.展开更多
Vertically stacked transition metal dichalcogenide(TMD)heterostructures provide an opportunity to explore optoelectronic properties within the two-dimensional limit.In such structures,spatially indirect interlayer exc...Vertically stacked transition metal dichalcogenide(TMD)heterostructures provide an opportunity to explore optoelectronic properties within the two-dimensional limit.In such structures,spatially indirect interlayer excitons(IXs)can be generated in adjacent layers because of strong Coulomb interactions.However,due to the complexity of the multilayered heterostructure(HS),the capture and study of the IXs in trilayer type-Ⅱ HSs have so far remained elusive.Here,we present the observation of the IXs in trilayer type-Ⅱ staggered band alignment of MoS_(2)/MoSe_(2)/WSe_(2) van der Waals(vdW)HSs by photoluminescence(PL)spectroscopy.The central energy of IX is 1.33 eV,and the energy difference between the extracted double peaks is 23 meV.We confirmed the origin of IX through PL properties and calculations by the density functional theory,we also studied the dependence of the IX emission peak on laser power and temperature.Furthermore,the polarization-resolved PL spectra of HS were also investigated,and the maximum polarizability of the emission peak of WSe_(2) reached 11.40%at 6 K.Our findings offer opportunities for the study of new physical properties of excitons in TMD HSs and therefore are valuable for exploring the potential applications of TMDs in optoelectronic devices.展开更多
van der Waals (vdWs) heterostructures based on two-dimensional (2D) materials have become a promising candidate for photoelectrochemical (PEC) catalyst not only because of the freedom in materials design that enable t...van der Waals (vdWs) heterostructures based on two-dimensional (2D) materials have become a promising candidate for photoelectrochemical (PEC) catalyst not only because of the freedom in materials design that enable the band-offset construction and facilitate the charge separation. They also provide a platform for the study of various of interface effect in PEC. Here, we report a new kind of mixed-dimensional vdWs heterostructure photoelectrode and investigate the strain enhanced PEC performance at vdWs interfaces. Our heterostructures are composed of 2D n-type MoS_(2) nanosheets and three-dimensional (3D) p-type Cu_(2)O nanorod arrays (NRAs), where Cu_(2)O NRAs introduce periodically strain in the p-n junction interface. We find a promotion of the HER catalytic activities in heterostructure based PEC photoelectrodes using in-situ measurement techniques including the scanning electrochemical cell microscopy and various local spectrum probe measurements. This is attributed to the efficient charge separation at the strained heterointerface. Our results demonstrate an interesting venue for understanding the local interface effects with high spatial resolution, and shed light on design and developing high-efficiency photoelectrodes. 1L MoS_(2)/Cu_(2)O vdWs heterostructure photocathodes were prepared by nanoindentation technology. The effects of strain on promoting charge separation at the heterointerface were verified by the enhanced performances in PEC hydrogen evolution reaction of vdWs heterostructure through scanning electrochemical cell microscopy technique and various local spectrum probe measurements.展开更多
基金supported this research endeavor.Notably,the National Natural Science Foundation of China(No.52373311)the Science Talent Program of China,the Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)+10 种基金the Hunan Province Key Research and Development Project(No.2019GK2233)the Youth Innovation Team(No.2019012)of Central South University(CSU)have played an essential role in facilitating the success of this study.Furthermore,the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the Key Program of the Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the National Natural Science Foundation of China(Nos.62090035 and U19A2090)have also made significant contributions to the advancement of this workThe support provided by the High-Performance Complex Manufacturing Key State Lab Project at CSU(No.ZZYJKT2020-12)has been of immeasurable value,greatly expediting the research processAcknowledgment is also extended to the Australian Research Council(ARC Discovery Project,DP180102976)for its pivotal role in driving forward this research agenda.AdditionallyJ.T.W.extends gratitude for the support received from the National Natural Science Foundation of China(Nos.92263202 and 11974387)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB33000000)the National Key Research and Development Program of China(No.2020YFA0711502)The authors also wish to convey their deep appreciation to the Beijing Super Cloud Computing Center(BSCC,http://www.blsc.cn)for granting access to high-performance computing(HPC)resources,which have been instrumental in yielding the research outcomes detailed in this paper.Finally,the authors hold profound gratitude for the support of the Postdoctoral Science Foundation of China(No.2022M713546)a vital contribution that has substantially propelled the advancement of this research endeavor.This work was supported in part by the High-Performance Computing Center of Central South University.
文摘Moirésuperlattices,arising from the controlled twisting of van der Waals homostructures at specific angles,have emerged as a promising platform for quantum emission applications.Concurrently,the manipulation of strain provides a versatile strategy to finely adjust electronic band structures,enhance exciton luminescence efficiency,and establish a robust foundation for two-dimensional quantum light sources.However,the intricate interplay between strain and moirépotential remains partially unexplored.Here,we introduce a meticulously designed fusion of strain engineering and the twisted 2L-WSe_(2)/2L-WSe_(2) homobilayers,resulting in the precise localization of moiréexcitons.Employing low-temperature photoluminescence spectroscopy,we unveil the emergence of highly localized moiré-enhanced emission,characterized by the presence of multiple distinct emission lines.Furthermore,our investigation demonstrates the effective regulation of moirépotential depths through strain engineering,with the potential depths of strained and unstrained regions differing by 91%.By combining both experimental and theoretical approaches,our study elucidates the complex relationship between strain and moirépotential,thereby opening avenues for generating strain-induced moiréexciton single-photon sources.
基金the National Natural Science Foundation of China(No.61775241)Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)+3 种基金the Youth Innovation Team(No.2019012)of CSU,Hunan province key research and development project(No.2019GK2233)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)support of the High-Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)Z.W.L.thanks the support from the Australian Research Council(ARC Discovery Project,DP180102976).
文摘The formation of moirésuperlattices in twisted van der Waals(vdW)homostructures provides a versatile platform for designing the electronic band structure of two-dimensional(2D)materials.In graphene and transition metal dichalcogenides(TMDs)moirésystems,twist angle has been shown to be a key parameter for regulating the moirésuperlattice.However,the effect of the modulation of the twist angle on moirépotential and interlayer coupling has not been the subject of experimental investigation.Here,we report the observation of the modulation of moirépotential and intralayer excitons in the WS_(2)/WS_(2)homostructure.By accurately adjusting the torsion angle of the homobilayers,the depth of the moirépotential can be modulated.The confinement effect of the moirépotential on the intralayer excitons was further demonstrated by the changing of temperature and valley polarization.Furthermore,we show that a detection of atomic reconstructions by the low-frequency Raman mapping to map out inhomogeneities in moirélattices on a large scale,which endows the uniformity of interlayer coupling.Our results provide insights for an in-depth understanding of the behaviors of moiréexcitons in the twisted van der Waals homostructure,and promote the study of electrical engineering and topological photonics.
基金The authors would like to acknowledge the National Natural Science Foundation of China(Nos.61775241,62090035,and U19A2090)the Hunan Province Key Research and Development Project(No.2019GK2233)+8 种基金the Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)the Youth Innovation Team of CSU(No.2019012)the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the Postdoctoral Science Foundation of China(No.2022M713546)The authors would also like to express their gratitude to the High-Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)the Australian Research Council(ARC)Discovery Project(No.DP180102976)for their support of Z.W.L.C.T.W.acknowledges support from the National Natural Science Foundation of China(No.11974387)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB33000000)H.H.Z.is grateful for the support from the Postdoctoral Science Foundation of China(No.2022M713546).
文摘Exploiting the valley degrees of freedom as information carriers provides new opportunities for the development of valleytronics.Monolayer transition metal dichalcogenides(TMDs)with broken space-inversion symmetry exhibit emerging valley pseudospins,making them ideal platforms for studying valley electronics.However,intervalley scattering of different energy valleys limits the achievable degree of valley polarization.Here,we constructed WSe_(2)/yttrium iron garnet(YIG)heterostructures and demonstrated that the interfacial magnetic exchange effect on the YIG magnetic substrate can enhance valley polarization by up to 63%,significantly higher than that of a monolayer WSe_(2)on SiO_(2)/Si(11%).Additionally,multiple sharp exciton peaks appear in the WSe_(2)/YIG heterostructures due to the strong magnetic proximity effect at the magnetic-substrate interface that enhances exciton emission efficiency.Moreover,under the effect of external magnetic field,the magnetic direction of the magnetic substrate enhances valley polarization,further demonstrating that the magnetic proximity effect regulates valley polarization.Our results provide a new way to regulate valley polarization and demonstrate the promising application of magnetic heterojunctions in magneto-optoelectronics.
基金The authors express their gratitude to various organizations for their support in this research,including the National Natural Science Foundation of China(Grant No.61775241)the Hunan province key research and development project(Grant No.2019GK2233)+8 种基金the Hunan Provincial Science Fund for Distinguished Young Scholars(Grant No.2020JJ2059)the Youth Innovation Team(Grant No.2019012)of CSU.Additionally,they acknowledge the Science and Technology Innovation Basic Research Project of Shenzhen(Grant No.JCYJ20190806144418859)the National Natural Science Foundation of China(Nos.62090035 and U19A2090)the Key Program of Science and Technology Department of Hunan Province(2019XK2001,2020XK2001)The authors also thank the High-Performance Complex Manufacturing Key State Lab Project of Central South University(Grant No.ZZYJKT2020-12)for their support.Z.W.Lacknowledges the support from the Australian Research Council(ARC Discovery Project,DP180102976)C.T.W.is grateful for the support from the National Natural Science Foundation of China(Grant No.11974387)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB33000000)H.H.Z.acknowledges the support from the Postdoctoral Science Foundation of China(2022M713546).Finally,the authors recognize the Beijing Super Cloud Computing Center(BSCC)for providing HPC resources,which have greatly contributed to the results reported in this paper.
文摘The stacking of twisted two-dimensional(2D)layered materials has led to the creation of moirésuperlattices,which have become a new platform for the study of quantum optics.The strong coupling of moirésuperlattices can result in flat minibands that boost electronic interactions and generate interesting strongly correlated states,including unconventional superconductivity,Mott insulating states,and moiréexcitons.However,the impact of adjusting and localizing moiréexcitons in Van der Waals heterostructures has yet to be explored experimentally.Here,we present experimental evidence of the localization-enhanced moiréexcitons in the twisted WSe_(2)/WS_(2)/WSe_(2)heterotrilayer with type-II band alignments.At low temperatures,we observed multiple excitons splitting in the twisted WSe_(2)/WS_(2)/WSe_(2)heterotrilayer,which is manifested as multiple sharp emission lines,in stark contrast to the moiréexcitonic behavior of the twisted WSe_(2)/WS_(2)heterobilayer(which has a linewidth 4 times wider).This is due to the enhancement of the two moirépotentials in the twisted heterotrilayer,enabling highly localized moiréexcitons at the interface.The confinement effect of moirépotential on moiréexcitons is further demonstrated by changes in temperature,laser power,and valley polarization.Our findings offer a new approach for localizing moiréexcitons in twist-angle heterostructures,which has the potential for the development of coherent quantum light emitters.
基金the National Natural Science Foundation of China(No.61775241)Hunan province key research and development project(No.2019GK2233)+9 种基金Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)the Youth Innovation Team(No.2019012)of CSUthe Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the National Natural Science Foundation of China(Nos.62090035 and U19A2090)the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)support of the High-Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)the Australian Research Council(ARC Discovery Project,No.DP180102976)the National Natural Science Foundation of China(No.11974387)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB33000000)the National Key Research and Development Program of China(No.2020YFA0711502).
文摘Recently,the discovery of a variety of moiré-related properties in the twisted vertical stacking of two different monolayers has attracted considerable attention.The introduction of small twist angles in transition metal dichalcogenide(TMD)heterostructures leads to the emergence of moirépotentials,which provide a fascinating platform for the study of strong interactions of electrons.While there has been extensive research on moiréexcitons in twisted bilayer superlattices,the capture and study of moiréexcitons in homostructure superlattices with layer-coupling effects remain elusive.Here,we present the observation of moiréexcitons in the twisted 1L-WSe_(2)/1L-WSe_(2)and 1L-WSe_(2)/2L-WSe_(2)homostructures with various layer-coupling interactions.The results reveal that the moirépotential increases(~260%)as the number of underlying layers decreases,indicating the effect of layer coupling on the modulation of the moirépotential.The effects of the temperature and laser power dependence as well as valley polarization on moiréexcitons were further demonstrated,and the crucial spectral features observed were explained.Our findings pave the way for exploring quantum phenomena and related applications of quantum information.
基金The study presented herein was generously supported by multiple funding agencies,including the National Natural Science Foundation of China(No.61775241)the Hunan Province Key Research and Development Project(No.2019GK2233)+9 种基金the Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)the National Natural Science Foundation of China(Nos.62090035 and U19A2090)the Youth Innovation Team(No.2019012)of CSU,the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the Postdoctoral Science Foundation of China(No.2022M713546)The authors also express their gratitude to the High-Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)the Australian Research Council(ARC Discovery Project,DP180102976)for their support of ZWLCTW is grateful for support from the National Natural Science Foundation of China(No.11974387)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB33000000)H.H.Z.acknowledges support from the Postdoctoral Science Foundation of China(No.2022M713546).
文摘Moirésuperlattices in van der Waals structures have emerged as a powerful platform for studying the novel quantum properties of two-dimensional materials.The periodic moirépatterns generated by these structures lead to the formation of flat mini-bands,which alter the electronic energy bands of the material.The resulting flat electronic bands can greatly enhance strong correlative interactions between electrons,leading to the emergence of exotic quantum phenomena,including moiréphonons and moiréexcitons.While extensive research has been conducted on the exotic quantum phenomena in twisted bilayers of transition metal dichalcogenides(TMDs),and the regulatory effect of stacked layers on moiréexcitons remains unexplored.In this study,we report the fabrication of a twisted WSe_(2)/WSe_(2)/WSe_(2) homotrilayer with two twist angles and investigate the influence of stacked layers on moiréexcitons.Our experiments reveal multiple moiréexciton splitting peaks in the twisted trilayer,with moirépotential depths of 78 and 112 meV in the bilayer and trilayer homostructures,respectively.We also observed the splitting of the moiréexcitons at 90 K,indicating the presence of a deeper moirépotential in the twisted trilayer.Moreover,we demonstrate that stacked layers can tune the moiréexcitons by manipulating temperature,laser power,and magnetic field.Our results provide a new physical model for studying moirésuperlattices and their quantum properties,which could potentially pave the way for the development of quantum optoelectronics.
基金support from the Naional Natural Science Foundation of China(Grant No.61775241)Hunan province key research and development project(Grant No.2019GK2233)+5 种基金Hunan Provincial Science Fund for Distinguished Young Scholars(Grant No.2020JJ2059)the Youth Innovaticn Team(Grant No.2019012)of CSU,the Science and Technolgy Innovaton Basic Research Project of Shenzhen(Grant No.JCY120190806144418859)the National Natural Science Foundation of China (Nos.62090035,U19A2090)the Key Program of Science and Technology Department of Hunan Province(2019XK2001,2020XK2001)support of the High-Performance Complex Manufacturing Key State Lab Project,Central South University(Grant No.ZZYJKT2020-12)ZWL.thanks the support from the Australian Research Council(ARC Discovery Project,DP180102976).
文摘Recent advances in twisted van der Waals heterostructure superlattices have emerged as a powerful and attractive platform for exploring novel condensed matter physics due to the interplay between the moirépotential and Coulomb interactions.The moirésuperlattices act as a periodic confinement potential in space to capture interlayer excitons(IXs),resulting in moiréexciton arrays,which provide opportunities for quantum emitters and many-body physics.The observation of moiréIXs in twisted transition-metal dichalcogenide(TMD)heterostructures has recently been widely reported.However,the capture and study of the moiréintralayer excitons based on TMD twisted homobilayer(T-HB)remain elusive.Here,we report the observation of moiréintralayer excitons in a WSe_(2)/WSe_(2) T-HB with a small twist angle by measuring PL spectrum.The multiple split peaks with an energy range of 1.55-1.73 eV are different from that of the monolayer WSe_(2) exciton peaks.The split peaks were caused by the trapping of intralayer excitons via the moirépotential.The confinement effect of the moirépotential on the moiréintralayer excitons was further demonstrated by the changing of temperature,laser power,and valley polarization.Our findings provide a new avenue for exploring new correlated quantum phenomena and their applications.
基金support from the National Natural Science Foundation of China(Nos.61775241,62090035,and U19A2090)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20180307151237242)+5 种基金Hunan Province Key Research and Development Project(No.2019GK2233)Hunan Provincial Science Fund for Distinguished Young Scholars(No,2020JJ2059)the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the Youth Innovation Team(No,2019012)of Central South UniversityThe authors are also thankful for the support of the High Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)Z.W.L.thanks the support from the Australian Research Council(ARC Discovery Project,No.DP180102976).
文摘Van der Waals heterostructures have recently emerged,in which two distinct transitional metal dichalcogenide(TMD)monolayers are stacked vertically to generate interlayer excitons(IXs),offing new opportunites for the design of optoelectronic devices.However,the bilayer heterostructure with type-II band alignment can only produce low quantum yield.Here,we present the observation of interlayer neutral excitons and trions in the MoSe_(2)/MoS_(2)/MoSe_(2)trilayer heterostructure(Tri-HS).In comparison to the 8 K bilayer heterostructure,the addition of a MoSe_(2)layer to the Tri-HS can significantly increase the quantum yield of IXs.It is believed the two symmetrical type-II band alignments formed in the Tri-HS could effectively promote the IX radiation recombination.By analyzing the photoluminescence(PL)spectrum of the IXs at cryogenic temperature and the power dependence,the existence of the interlayer trions was confirmed.Our results provide a promising platform for the development of more efficient optoelectronic devices and the investigation of new physical properties of TMDs.
基金the National Natural Science Foundation of China(No.61775241)Hunan province key research and development project(No.2019GK2233)+6 种基金Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)the Youth Innovation Team(No.2019012)of CSUthe Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the National Natural Science Foundation of China(Nos.62090035 and U19A2090)the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the support of the High-Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)Z.W.L.thanks the support from the Australian Research Council(ARC Discovery Project,DP180102976).
文摘Moirésuperlattices are formed by a lattice mismatch or twist angle in two-dimensional materials,which can generate periodical moirépotentials leading to strong changes in the band structure,resulting in new quantum phenomena.However,the experimental engineering of in-situ deformation of moiréheterostructures remains deficient.Here,we demonstrate a dynamic local deformation of the twisted heterostructures using a diamond anvil cell(DAC),enabling in-situ dynamic modulation of moirépotential in twisted WS_(2)–WSe_(2)heterostructures at room temperature.Deformation of the twisted heterostructure increases the moirépotential,causing a red shift of the moiréexciton resonance,and observed the red shift of the intralayer exciton resonance up to 16.3 meV(less than 1.1 GPa).The blue shift of the interlayer excitons of twisted WS_(2)–WSe_(2)heterostructures shows an evident transition of the pressure sensitive exciton,induced by the dominant effect of modifying the band structure on optical properties.Combined with the spectral changes of pressurized Raman,which further demonstrated that the DAC can efficiently regulate the interlayer coupling.Our results offer an effective strategy for in-situ dynamic modulation of moirépotential,providing a promising platform for the development of novel quantum devices.
基金the support of the Hunan Province’s Key Research and Development Project(No.2019GK2233)the National Natural Science Foundation of China(No.61775241)+4 种基金the Hunan Science Fund for Distinguished Young Scholar(No.2020JJ2059)Youth Innovation Team(No.2019012)of CSU,Hunan Province Graduate Research and Innovation Project(No.CX20190177)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the support from the Central South University of the State Key Laboratory of High-Performance Complex Manufacturing Project(No.ZZYJKT2020-12).support from the Australian Research Council(ARC Discovery Projects,Nos.DP210103539,DP180102976,and DP130104231).
文摘Vertically stacked transition metal dichalcogenide(TMD)heterostructures provide an opportunity to explore optoelectronic properties within the two-dimensional limit.In such structures,spatially indirect interlayer excitons(IXs)can be generated in adjacent layers because of strong Coulomb interactions.However,due to the complexity of the multilayered heterostructure(HS),the capture and study of the IXs in trilayer type-Ⅱ HSs have so far remained elusive.Here,we present the observation of the IXs in trilayer type-Ⅱ staggered band alignment of MoS_(2)/MoSe_(2)/WSe_(2) van der Waals(vdW)HSs by photoluminescence(PL)spectroscopy.The central energy of IX is 1.33 eV,and the energy difference between the extracted double peaks is 23 meV.We confirmed the origin of IX through PL properties and calculations by the density functional theory,we also studied the dependence of the IX emission peak on laser power and temperature.Furthermore,the polarization-resolved PL spectra of HS were also investigated,and the maximum polarizability of the emission peak of WSe_(2) reached 11.40%at 6 K.Our findings offer opportunities for the study of new physical properties of excitons in TMD HSs and therefore are valuable for exploring the potential applications of TMDs in optoelectronic devices.
基金supported by the National Key R&D Program of China (Nos. 2018YFA0306900 and 2018YFA0209500)the National Natural Science Foundation of China (Nos. 21872114,21972121 and 21908253)+4 种基金the Science and Technology Plan Project of Guangdong Province (No. 2018A030310300)the China Postdoctoral Science Foundation (No. 2020M682616)Donors of the American Chemical Society Petroleum Research Fund for partial support of this research (No. 61155-DNI5)Defense Advanced Research Project Agency (DARPA)the Army Research Office for the financial support (No. W911NF-20-1-0304)。
文摘van der Waals (vdWs) heterostructures based on two-dimensional (2D) materials have become a promising candidate for photoelectrochemical (PEC) catalyst not only because of the freedom in materials design that enable the band-offset construction and facilitate the charge separation. They also provide a platform for the study of various of interface effect in PEC. Here, we report a new kind of mixed-dimensional vdWs heterostructure photoelectrode and investigate the strain enhanced PEC performance at vdWs interfaces. Our heterostructures are composed of 2D n-type MoS_(2) nanosheets and three-dimensional (3D) p-type Cu_(2)O nanorod arrays (NRAs), where Cu_(2)O NRAs introduce periodically strain in the p-n junction interface. We find a promotion of the HER catalytic activities in heterostructure based PEC photoelectrodes using in-situ measurement techniques including the scanning electrochemical cell microscopy and various local spectrum probe measurements. This is attributed to the efficient charge separation at the strained heterointerface. Our results demonstrate an interesting venue for understanding the local interface effects with high spatial resolution, and shed light on design and developing high-efficiency photoelectrodes. 1L MoS_(2)/Cu_(2)O vdWs heterostructure photocathodes were prepared by nanoindentation technology. The effects of strain on promoting charge separation at the heterointerface were verified by the enhanced performances in PEC hydrogen evolution reaction of vdWs heterostructure through scanning electrochemical cell microscopy technique and various local spectrum probe measurements.
