Engineering the electronic band structure of material systems enables the unprecedented exploration of new physical properties that are absent in natural or as-synthetic materials.Electronic structures of bilayer two-...Engineering the electronic band structure of material systems enables the unprecedented exploration of new physical properties that are absent in natural or as-synthetic materials.Electronic structures of bilayer two-dimensional(2D)systems can be flexibly engineered by the external electric field.For example.展开更多
During the past decades,transition metal dichalcogenides(TMDs) have received special focus for their unique properties in photoelectric detection.As one important member of TMDs,MoS2 has been made into photodetector p...During the past decades,transition metal dichalcogenides(TMDs) have received special focus for their unique properties in photoelectric detection.As one important member of TMDs,MoS2 has been made into photodetector purely or combined with other materials,such as graphene,ionic liquid,and ferroelectric materials.Here,we report a gate-free MoS2 phototransistor combined with organic ferroelectric material poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE)).In this device,the remnant polarization field in P(VDF-TrFE) is obtained from the piezoelectric force microscope(PFM) probe with a positive or negative bias,which can turn the dipoles from disorder to be the same direction.Then,the MoS2 channel can be maintained at an accumulated state with downward polarization field modulation and a depleted state with upward polarization field modulation.Moreover,the P(VDF-TrFE) segregates MoS2 from oxygen and water molecules around surroundings,which enables a cleaner surface state.As a photodetector,an ultra-low dark current of 10^–11 A,on/off ration of more than 10^4 and a fast photoresponse time of 120 μs are achieved.This work provides a new method to make high-performance phototransistors assisted by the ferroelectric domain which can operate without a gate electrode and demonstrates great potential for ultra-low power consumption applications.展开更多
OBJECTIVE: To investigate the effects of Yindanxinnaotong capsule(YDXNTC) and main components compatibility and ratios on myocardium against ischemia/reperfusion injury and the effect's underlying mechanism.METHOD...OBJECTIVE: To investigate the effects of Yindanxinnaotong capsule(YDXNTC) and main components compatibility and ratios on myocardium against ischemia/reperfusion injury and the effect's underlying mechanism.METHODS: Myocardial ischemia/reperfusion injury(MIRI) was induced by ischemia for 30 min and reperfusion for 30 min. Electrocardiogram data and coronary flow were recorded, and superoxide dismutase(SOD), malondialdehyde(MDA), lactate dehydrogenase, creatine kinase-MB, cardiac troponin T and I(cT nT, cT n I) and interleukin-1β, interleukin-8,interleukin-18(IL-1β, IL-8, IL-18) in myocardium were measured. Hypoxia/reoxygenation and hydrogen peroxide(H2O2) injury were induced by hypoxia for 3 h/reoxygenation for 2 h, and 100 μM H2O2 for 1 h, respectively, in vitro rat myocardial cells(H9c2). Cell viability, SOD, MDA, cT nT and inflamma-tory factors(IL-1β, IL-8 and IL-18) were determined,and Toll-like receptor 4(TLR-4) expression was measured by western blotting.RESULTS: In the isolated heart experiment, elevated heart function, coronary flow and SOD levels,and decreased MDA levels and inflammatory factors were noted in the YDXNTC, main components and main components compatibility groups. Ventricular tachycardia/ventricular fibrillation occurrence decreased in the ginkgo biloba extract(GBE),and GBE and salvia miltiorrhiza ethanol extract compatibility(SM-E, GSEC) groups. Lactic dehydrogenase levels decreased in the YDXNTC and aqueous extract of salvia miltiorrhiza(SM-H) groups. Creatine kinase-MB decreased with GBE, SM-E, SM-H and GSEC treatment, and cT n I and cT nT levels decreased with GSEC. In the in vitro cell study,YDXNTC and main components ratios improved cell viability and SOD levels, and suppressed MDA,cT nT and inflammatory factors. TLR-4 expression was down-regulated.CONCLUSION: YDXNTC and main components compatibility showed protective effects on MIRI in this rat model and in vitro study. Regulating the Toll-like receptor signaling pathway may affect the mechanism.展开更多
OBJECTIVE： To investigate the anti-breast cancer （BC） effects and mechanisms of action of Xihuang pill （XHP） by conducting in vitro experiments on hu- man BC cell lines. METHODS： Two human BC cell lines （MCF-7 ...OBJECTIVE： To investigate the anti-breast cancer （BC） effects and mechanisms of action of Xihuang pill （XHP） by conducting in vitro experiments on hu- man BC cell lines. METHODS： Two human BC cell lines （MCF-7 and MDA- MB231） were cultured and treated with XHP. Cell viability was detected using the 3-（4, 5-Dimeth- ylthiazol-2-yl）-2, 5-diphenyltetrazolium bromide （MTT） assay. Flow cytometry was used to measure the cell cycle and apoptosis. The cell cycle was ana- lyzed with propidium iodide staining. Apoptosis was evaluated using the Annexin V-fluorescein iso- thiocyanate/propidium iodide method. Western blotting was used to analyze the expression of es- trogen receptor （ER）-α and ER-13.RESULTS： XHP had growth-inhibitory effects on MCF-7 and MDA-MB231 cells with a half-maximal inhibitory concentration （IC50） of 10.14 mg/mL （MCF-7） and 8.98 mg/mL （MDA-MB231）. Apoptosis was induced to some extent. Certain changes in the ER were caused. Upregulation of ER-a protein was found in MCF-7 cells. ER-β expression in MDA-MB231 cells was increased. Cell-cycle arrest was not observed in the two BC cell lines. ER-β ex- pression in MCF-7 cells was unchanged. No ER-a ex- pression was shown in MDA-MB231 cells. CONCLUSION： These data suggest that XHP can af- fect cell viability and cause apoptosis, but that the cell cycle is not blocked. XHP has a certain impact on ER expression, but its mechanisms of action of anti-13C effects may not be due to regulation of ER expression.展开更多
Two-dimensional material(2D)that possesses atomic thin geometry and remarkable properties is a star material for the fundamental researches and advanced applications.Defects in 2D materials are critical and fundamenta...Two-dimensional material(2D)that possesses atomic thin geometry and remarkable properties is a star material for the fundamental researches and advanced applications.Defects in 2D materials are critical and fundamental to understand the chemical,physical,and optical properties.Photoluminescence arises in 2D materials owing to various physical phenomena including activator/dopant-induced luminescence and defect-related emissions,and so forth.With the advanced transmission electron microscopy(TEM)technologies,such as aberration correction and low voltage technologies,the morphology,chemical compositions and electronic structures of defects in 2D material could be directly characterized at the atomic scale.In this review,we introduce the applications of state-of-the-art TEM technologies on the studies of the role of atomic defects in the photoluminescence characteristics in 2D material.The challenges in spatial and time resolution are also discussed.It is proved that TEM is a powerful tool to pinpoint the relationship between the defects and the photoluminescence characteristics.展开更多
Two-dimensional(2D)materials have attracted increasing attention for their outstanding structural and electrical properties.However,for mass-production of field effect transistors(FETs)and potential applications in in...Two-dimensional(2D)materials have attracted increasing attention for their outstanding structural and electrical properties.However,for mass-production of field effect transistors(FETs)and potential applications in integrated circuits,large-area and uniform 2D thin films with high mobility,large on-off ratio,and desired polarity are needed to synthesize firstly.Here,a transfer-free growth method for platinum diselenide(PtSe2)films has been developed.The PtSe2 films have been synthesized with various thicknesses in centimeter-sized scale.Typical FET made from a few layer PtSe2 show p-type unipolar,with a high field-effect hole mobility of 6.2 cm^(2) V^(−1) s^(−1) and an on-off ratio of 5×10^(3).The versatile semimetal-unipolar-ambipolar transition in synthesized PtSe2 films is also firstly observed as the thickness thinning.This work realizes the large-scale preparation of PtSe2 with prominent electrical properties and provides a new strategy for polarity's modulation.展开更多
The advent of low-dimensional materials with peculiar structure and superb band properties provides a new canonical form for the development of photodetectors.However,the limited exploitation of basic properties makes...The advent of low-dimensional materials with peculiar structure and superb band properties provides a new canonical form for the development of photodetectors.However,the limited exploitation of basic properties makes it difficult for devices to stand out.Here,we demonstrate a hybrid heterostructure with ultrathin vanadium dioxide film and molybdenum ditelluride nanoflake.Vanadium dioxide is a classical semiconductor with a narrow bandgap,a high temperature coefficient of resistance,and phase transformation.Molybdenum ditelluride,a typical two-dimensional material,is often used to construct optoelectronic devices.The heterostructure can realize three different functional modes:(i)the p-n junction exhibits ultrasensitive detection(450 nm-2μm)with a dark current down to 0.2 pA and a response time of 17μs,(ii)the Schottky junction works stably under extreme conditions such as a high temperature of 400 K,and(iii)the bolometer shows ultrabroad spectrum detection exceeding 10μm.The flexible switching between the three modes makes the heterostructure a potential candidate for next-generation photodetectors from visible to longwave infrared radiation(LWIR).This type of photodetector combines versatile detection modes,shedding light on the hybrid application of novel and traditional materials,and is a prototype of advanced optoelectronic devices.展开更多
Light polarization could provide critical visual information(e.g., surface roughness, geometry, or orientation) of the imaged objects beyond prevailing signals of intensity and wavelength. The polarization imaging tec...Light polarization could provide critical visual information(e.g., surface roughness, geometry, or orientation) of the imaged objects beyond prevailing signals of intensity and wavelength. The polarization imaging technology thus has a large potential in broad fields such as object detection. However, intricate polarization coding is often required in these fields, and the existing complicated lensed system and polarizers have limited the miniaturization capabilities of the integrated imaging sensor. In this study, we demonstrate the utilization of two-dimensional(2 D) in-plane anisotropic α-Ge Se semiconductor to realize the polarizer-free polarization-sensitive visible/near-infrared(VIS-NIR) photodetector/imager. As the key part of the sensor system, this prototype Au/Ge Se/Au photodetector exhibits impressive performances in terms of high sensitivity, broad spectral response, and fast-speed operation(~10^(3) A W^(-1), 400–1050 nm,and 22.7/49.5 μs). Further, this device demonstrates unique polarization sensitivity in the spectral range of 690–1050 nm and broadband absorption of light polarized preferentially in the y-direction, as predicted by the analysis of optical transition behavior in α-Ge Se. Then we have successfully incorporated the 2 D Ge Se device into an imaging system for the polarization imaging and captured the polarization information of the radiant target with a high contrast ratio of 3.45 at808 nm(NIR band). This proposed imager reveals the ability to sense dual-band polarization signals in the scene withoutpolarizers and paves the way for polarimetric imaging sensor arrays for advanced applications.展开更多
Manganese oxides with a perovskite-type Re_(1-x)D_xMnO_3(Re:heavy rare-earth elements,D:divalent alkali metal)structure have attracted interest because of the complex interaction between their electrons,lattices,and s...Manganese oxides with a perovskite-type Re_(1-x)D_xMnO_3(Re:heavy rare-earth elements,D:divalent alkali metal)structure have attracted interest because of the complex interaction between their electrons,lattices,and spins[1-5].Generally,manganese oxides with the structure Re_(1-x)D_xMnO_3 have special properties.For example,the half-metallic manganites,such as La_(2/3)Sr_(1/3)MnO_3 and La_(2/3)Ca_(1/3)MnO_3,wherein the conduction electrons are completely spin polarized。展开更多
The large tunability in the band structure is ubiquitous in two-dimensional(2D)materials,and PtSe_(2) is not an exception,which has attracted considerable attention in electronic and optoelectronic applications due to...The large tunability in the band structure is ubiquitous in two-dimensional(2D)materials,and PtSe_(2) is not an exception,which has attracted considerable attention in electronic and optoelectronic applications due to its high carrier mobility and long-term airstability.Such dimensional dependent properties are closely related to the evolution of electronic band structures.Critical points(CPs),the extrema or saddle points of electronic bands,are the cornerstone of condensed-matter physics and fundamentally determine the optical and transport phenomena of the layered PtSe_(2).Here,we have experimentally revealed the detailed electronic structures in layered PtSe_(2),including the CPs in the Brillouin zones(BZs),by means of reflection contrast spectroscopy and spectroscopic ellipsometry(SE).There are three critical points in the BZs attributed to the excitonic transition,quasi-particle band gap,and the band nesting effect related transition,respectively.Three CPs show red-shifting trends with increasing layer number under the mechanism of strong interlayer coupling.We have further revealed the electron–phonon(e–ph)interaction in such layered material,utilizing temperature-dependent absorbance spectroscopy.The strength of e–ph interaction and the average phonon energy also decline with the increasement of layer number.Our findings give a deep understanding to the physics of the layer-dependent evolution of the electronic structure of PtSe_(2),potentially leading to applications in optoelectronics and electronic devices.展开更多
文摘Engineering the electronic band structure of material systems enables the unprecedented exploration of new physical properties that are absent in natural or as-synthetic materials.Electronic structures of bilayer two-dimensional(2D)systems can be flexibly engineered by the external electric field.For example.
基金supported by the Major State Basic Research Development Program (Grant Nos. 2016YFA0203900, 2016YFB0400801 and 2015CB921600)Key Research Project of Frontier Sciences of Chinese Academy of Sciences (Nos. QYZDB-SSW-JSC016, QYZDY-SSW-JSC042)+2 种基金Strategic Priority Research Program of Chinese Academy of Sciences (XDPB12, XDB 3000000)Natural Science Foundation of China (Grant Nos. 61521001, 61574151, 61574152, 61674158, 61722408, 61734003 and 61835012)Natural Science Foundation of Shanghai (Grant No. 16ZR1447600, 17JC1400302)
文摘During the past decades,transition metal dichalcogenides(TMDs) have received special focus for their unique properties in photoelectric detection.As one important member of TMDs,MoS2 has been made into photodetector purely or combined with other materials,such as graphene,ionic liquid,and ferroelectric materials.Here,we report a gate-free MoS2 phototransistor combined with organic ferroelectric material poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE)).In this device,the remnant polarization field in P(VDF-TrFE) is obtained from the piezoelectric force microscope(PFM) probe with a positive or negative bias,which can turn the dipoles from disorder to be the same direction.Then,the MoS2 channel can be maintained at an accumulated state with downward polarization field modulation and a depleted state with upward polarization field modulation.Moreover,the P(VDF-TrFE) segregates MoS2 from oxygen and water molecules around surroundings,which enables a cleaner surface state.As a photodetector,an ultra-low dark current of 10^–11 A,on/off ration of more than 10^4 and a fast photoresponse time of 120 μs are achieved.This work provides a new method to make high-performance phototransistors assisted by the ferroelectric domain which can operate without a gate electrode and demonstrates great potential for ultra-low power consumption applications.
基金the Major National Science and Technology Projects:the Technology Reformation of Yindanxinnaotong Capsule(No.2012ZX09201201)
文摘OBJECTIVE: To investigate the effects of Yindanxinnaotong capsule(YDXNTC) and main components compatibility and ratios on myocardium against ischemia/reperfusion injury and the effect's underlying mechanism.METHODS: Myocardial ischemia/reperfusion injury(MIRI) was induced by ischemia for 30 min and reperfusion for 30 min. Electrocardiogram data and coronary flow were recorded, and superoxide dismutase(SOD), malondialdehyde(MDA), lactate dehydrogenase, creatine kinase-MB, cardiac troponin T and I(cT nT, cT n I) and interleukin-1β, interleukin-8,interleukin-18(IL-1β, IL-8, IL-18) in myocardium were measured. Hypoxia/reoxygenation and hydrogen peroxide(H2O2) injury were induced by hypoxia for 3 h/reoxygenation for 2 h, and 100 μM H2O2 for 1 h, respectively, in vitro rat myocardial cells(H9c2). Cell viability, SOD, MDA, cT nT and inflamma-tory factors(IL-1β, IL-8 and IL-18) were determined,and Toll-like receptor 4(TLR-4) expression was measured by western blotting.RESULTS: In the isolated heart experiment, elevated heart function, coronary flow and SOD levels,and decreased MDA levels and inflammatory factors were noted in the YDXNTC, main components and main components compatibility groups. Ventricular tachycardia/ventricular fibrillation occurrence decreased in the ginkgo biloba extract(GBE),and GBE and salvia miltiorrhiza ethanol extract compatibility(SM-E, GSEC) groups. Lactic dehydrogenase levels decreased in the YDXNTC and aqueous extract of salvia miltiorrhiza(SM-H) groups. Creatine kinase-MB decreased with GBE, SM-E, SM-H and GSEC treatment, and cT n I and cT nT levels decreased with GSEC. In the in vitro cell study,YDXNTC and main components ratios improved cell viability and SOD levels, and suppressed MDA,cT nT and inflammatory factors. TLR-4 expression was down-regulated.CONCLUSION: YDXNTC and main components compatibility showed protective effects on MIRI in this rat model and in vitro study. Regulating the Toll-like receptor signaling pathway may affect the mechanism.
基金Supported by the Beijing Traditional Chinese Medicine Science and Technology Project(QN2010-3)National Natural Science Foundation of China(No.81001564)
文摘OBJECTIVE： To investigate the anti-breast cancer （BC） effects and mechanisms of action of Xihuang pill （XHP） by conducting in vitro experiments on hu- man BC cell lines. METHODS： Two human BC cell lines （MCF-7 and MDA- MB231） were cultured and treated with XHP. Cell viability was detected using the 3-（4, 5-Dimeth- ylthiazol-2-yl）-2, 5-diphenyltetrazolium bromide （MTT） assay. Flow cytometry was used to measure the cell cycle and apoptosis. The cell cycle was ana- lyzed with propidium iodide staining. Apoptosis was evaluated using the Annexin V-fluorescein iso- thiocyanate/propidium iodide method. Western blotting was used to analyze the expression of es- trogen receptor （ER）-α and ER-13.RESULTS： XHP had growth-inhibitory effects on MCF-7 and MDA-MB231 cells with a half-maximal inhibitory concentration （IC50） of 10.14 mg/mL （MCF-7） and 8.98 mg/mL （MDA-MB231）. Apoptosis was induced to some extent. Certain changes in the ER were caused. Upregulation of ER-a protein was found in MCF-7 cells. ER-β expression in MDA-MB231 cells was increased. Cell-cycle arrest was not observed in the two BC cell lines. ER-β ex- pression in MCF-7 cells was unchanged. No ER-a ex- pression was shown in MDA-MB231 cells. CONCLUSION： These data suggest that XHP can af- fect cell viability and cause apoptosis, but that the cell cycle is not blocked. XHP has a certain impact on ER expression, but its mechanisms of action of anti-13C effects may not be due to regulation of ER expression.
基金X.W.thanks the supported by the NSFC(61574060)the Projects of Science and Technology Commission of Shanghai Municipality(14DZ2260800)+2 种基金the Shanghai Rising-Star Program(17QA1401400)the Fundamental Research Funds for the Central Universities.Z.S.thanks the financial support from Australian Research Council through an ARC DECRA project(DE150100280)an ARC Future Fellow project(FT180100387).
文摘Two-dimensional material(2D)that possesses atomic thin geometry and remarkable properties is a star material for the fundamental researches and advanced applications.Defects in 2D materials are critical and fundamental to understand the chemical,physical,and optical properties.Photoluminescence arises in 2D materials owing to various physical phenomena including activator/dopant-induced luminescence and defect-related emissions,and so forth.With the advanced transmission electron microscopy(TEM)technologies,such as aberration correction and low voltage technologies,the morphology,chemical compositions and electronic structures of defects in 2D material could be directly characterized at the atomic scale.In this review,we introduce the applications of state-of-the-art TEM technologies on the studies of the role of atomic defects in the photoluminescence characteristics in 2D material.The challenges in spatial and time resolution are also discussed.It is proved that TEM is a powerful tool to pinpoint the relationship between the defects and the photoluminescence characteristics.
基金support from the National Natural Science Foundation of China(61835012,61722408,21771040,61574151,61574152)the Key Research Project of Frontier Sciences of Chinese Academy of Sciences(QYZDB-SSW-JSC016,QYZDB-SSW-JSC042)+1 种基金the National Key Research and Development Program of China(2017YFA0207303,2016YFA0203900)the 1000 Plan Program for Young Talents.
文摘Two-dimensional(2D)materials have attracted increasing attention for their outstanding structural and electrical properties.However,for mass-production of field effect transistors(FETs)and potential applications in integrated circuits,large-area and uniform 2D thin films with high mobility,large on-off ratio,and desired polarity are needed to synthesize firstly.Here,a transfer-free growth method for platinum diselenide(PtSe2)films has been developed.The PtSe2 films have been synthesized with various thicknesses in centimeter-sized scale.Typical FET made from a few layer PtSe2 show p-type unipolar,with a high field-effect hole mobility of 6.2 cm^(2) V^(−1) s^(−1) and an on-off ratio of 5×10^(3).The versatile semimetal-unipolar-ambipolar transition in synthesized PtSe2 films is also firstly observed as the thickness thinning.This work realizes the large-scale preparation of PtSe2 with prominent electrical properties and provides a new strategy for polarity's modulation.
基金supported by the Natural Science Foundation of China(Grant Nos.61835012,61722408,61725505,61521005,and 61905267)the Key Research Project of Frontier Sciences of the Chinese Academy of Sciences(Grant Nos.QYZDB-SSW-JSC016 and QYZDY-SSW-JSC042)+4 种基金the Key Research Program of Frontier Science,CAS(Grant No.ZDBS-LY-JSC045)the Major State Basic Research Development Program(Grant No.2016YFA0203900)the National Postdoctoral Program for Innovative Talents(BX20180329)the Natural Science Foundation of Shanghai(Grant Nos.16ZR1447600 and 17JC1400302)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB44000000).
文摘The advent of low-dimensional materials with peculiar structure and superb band properties provides a new canonical form for the development of photodetectors.However,the limited exploitation of basic properties makes it difficult for devices to stand out.Here,we demonstrate a hybrid heterostructure with ultrathin vanadium dioxide film and molybdenum ditelluride nanoflake.Vanadium dioxide is a classical semiconductor with a narrow bandgap,a high temperature coefficient of resistance,and phase transformation.Molybdenum ditelluride,a typical two-dimensional material,is often used to construct optoelectronic devices.The heterostructure can realize three different functional modes:(i)the p-n junction exhibits ultrasensitive detection(450 nm-2μm)with a dark current down to 0.2 pA and a response time of 17μs,(ii)the Schottky junction works stably under extreme conditions such as a high temperature of 400 K,and(iii)the bolometer shows ultrabroad spectrum detection exceeding 10μm.The flexible switching between the three modes makes the heterostructure a potential candidate for next-generation photodetectors from visible to longwave infrared radiation(LWIR).This type of photodetector combines versatile detection modes,shedding light on the hybrid application of novel and traditional materials,and is a prototype of advanced optoelectronic devices.
基金supported by the National Natural Science Foundation of China (61622406,61904015,11674310,61725505 and 11734016)the National Key Research and Development Program of China (2017YFA0207500)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences (XDB30000000)the “The Pearl River Talent Recruitment Program”(2019ZT08X639)Beijing National Laboratory for Molecular Sciences (BNLMS201908)。
文摘Light polarization could provide critical visual information(e.g., surface roughness, geometry, or orientation) of the imaged objects beyond prevailing signals of intensity and wavelength. The polarization imaging technology thus has a large potential in broad fields such as object detection. However, intricate polarization coding is often required in these fields, and the existing complicated lensed system and polarizers have limited the miniaturization capabilities of the integrated imaging sensor. In this study, we demonstrate the utilization of two-dimensional(2 D) in-plane anisotropic α-Ge Se semiconductor to realize the polarizer-free polarization-sensitive visible/near-infrared(VIS-NIR) photodetector/imager. As the key part of the sensor system, this prototype Au/Ge Se/Au photodetector exhibits impressive performances in terms of high sensitivity, broad spectral response, and fast-speed operation(~10^(3) A W^(-1), 400–1050 nm,and 22.7/49.5 μs). Further, this device demonstrates unique polarization sensitivity in the spectral range of 690–1050 nm and broadband absorption of light polarized preferentially in the y-direction, as predicted by the analysis of optical transition behavior in α-Ge Se. Then we have successfully incorporated the 2 D Ge Se device into an imaging system for the polarization imaging and captured the polarization information of the radiant target with a high contrast ratio of 3.45 at808 nm(NIR band). This proposed imager reveals the ability to sense dual-band polarization signals in the scene withoutpolarizers and paves the way for polarimetric imaging sensor arrays for advanced applications.
基金supported by the Major State Basic Research Development Program(Grant No.2013CB922302)the National Natural Science Foundation of China(Grant No.11374320)
文摘Manganese oxides with a perovskite-type Re_(1-x)D_xMnO_3(Re:heavy rare-earth elements,D:divalent alkali metal)structure have attracted interest because of the complex interaction between their electrons,lattices,and spins[1-5].Generally,manganese oxides with the structure Re_(1-x)D_xMnO_3 have special properties.For example,the half-metallic manganites,such as La_(2/3)Sr_(1/3)MnO_3 and La_(2/3)Ca_(1/3)MnO_3,wherein the conduction electrons are completely spin polarized。
基金supported by the National Key Research and Development Program of China(No.2021YFB2012601)the Fudan University-CIOMP Joint Fund(No.FC2019-006).
文摘The large tunability in the band structure is ubiquitous in two-dimensional(2D)materials,and PtSe_(2) is not an exception,which has attracted considerable attention in electronic and optoelectronic applications due to its high carrier mobility and long-term airstability.Such dimensional dependent properties are closely related to the evolution of electronic band structures.Critical points(CPs),the extrema or saddle points of electronic bands,are the cornerstone of condensed-matter physics and fundamentally determine the optical and transport phenomena of the layered PtSe_(2).Here,we have experimentally revealed the detailed electronic structures in layered PtSe_(2),including the CPs in the Brillouin zones(BZs),by means of reflection contrast spectroscopy and spectroscopic ellipsometry(SE).There are three critical points in the BZs attributed to the excitonic transition,quasi-particle band gap,and the band nesting effect related transition,respectively.Three CPs show red-shifting trends with increasing layer number under the mechanism of strong interlayer coupling.We have further revealed the electron–phonon(e–ph)interaction in such layered material,utilizing temperature-dependent absorbance spectroscopy.The strength of e–ph interaction and the average phonon energy also decline with the increasement of layer number.Our findings give a deep understanding to the physics of the layer-dependent evolution of the electronic structure of PtSe_(2),potentially leading to applications in optoelectronics and electronic devices.
