In high temperature cuprate superconductors,it was found that the superfluid density decreases with the increase of hole doping.One natural question is whether there exists normal fluid in the superconducting state in...In high temperature cuprate superconductors,it was found that the superfluid density decreases with the increase of hole doping.One natural question is whether there exists normal fluid in the superconducting state in the overdoped region.In this paper,we have carried out high-resolution ultra-low temperature laser-based angle-resolved photoemission measurements on a heavily overdoped Bi2212 sample with a T_(c) of 48 K.We find that this heavily overdoped Bi2212 remains in the strong coupling regime with 2Δ_(0)/(k_(B)T_(c))=5.8.The single-particle scattering rate is very small along the nodal direction(~5 meV) and increases as the momentum moves from the nodal to the antinodal regions.A hard superconducting gap opening is observed near the antinodal region with the spectral weight at the Fermi level fully suppressed to zero.The normal fluid is found to be negligibly small in the superconducting state of this heavily overdoped Bi2212.These results provide key information to understand the high T_(c) mechanism in the cuprate superconductors.展开更多
Magnetic topological states of matter provide a fertile playground for emerging topological physics and phenomena.The current main focus is on materials whose magnetism stems from 3d magnetic transition elements,e.g.,...Magnetic topological states of matter provide a fertile playground for emerging topological physics and phenomena.The current main focus is on materials whose magnetism stems from 3d magnetic transition elements,e.g.,MnBi_(2)Te_(4),Fe_(3)Sn_(2),and Co_(3)Sn_(2)S_(2).In contrast,topological materials with the magnetism from rare earth elements remain largely unexplored.Here we report rare earth antiferromagnet GdAuAl_(4)Ge_(2)as a candidate magnetic topological metal.Angle resolved photoemission spectroscopy(ARPES)and first-principles calculations have revealed multiple bulk bands crossing the Fermi level and pairs of low energy surface states.According to the parity and Wannier charge center analyses,these bulk bands possess nontrivial Z2 topology,establishing a strong topological insulator state in the nonmagnetic phase.Furthermore,the surface band pairs exhibit strong termination dependence which provides insight into their origin.Our results suggest GdAuAl_(4)Ge_(2)as a rare earth platform to explore the interplay between band topology,magnetism and f electron correlation,calling for further study targeting on its magnetic structure,magnetic topology state,transport behavior,and microscopic properties.展开更多
The simple kagome-lattice band structure possesses Dirac cones,flat band,and saddle point with van Hove singularities in the electronic density of states,facilitating the emergence of various electronic orders.Here we...The simple kagome-lattice band structure possesses Dirac cones,flat band,and saddle point with van Hove singularities in the electronic density of states,facilitating the emergence of various electronic orders.Here we report a titanium-based kagome metal CsTi_(3)Bi_(5)where titanium atoms form a kagome network,resembling its isostructural compound CsV_3Sb_5.Thermodynamic properties including the magnetization,resistance,and heat capacity reveal the conventional Fermi liquid behavior in the kagome metal CsTi_(3)Bi_(5)and no signature of superconducting or charge density wave(CDW)transition anomaly down to 85 m K.Systematic angle-resolved photoemission spectroscopy measurements reveal multiple bands crossing the Fermi level,consistent with the first-principles calculations.The flat band formed by the destructive interference of hopping in the kagome lattice is observed directly.Compared to Cs V_(3)Sb_(5),the van Hove singularities are pushed far away above the Fermi level in CsTi_(3)Bi_(5),in line with the absence of CDW.Furthermore,the first-principles calculations identify the nontrivial Z_(2)topological properties for those bands crossing the Fermi level,accompanied by several local band inversions.Our results suppose CsTi_(3)Bi_(5)as a complementary platform to explore the superconductivity and nontrivial band topology.展开更多
In our most recently published article,[1]an important reference[2]predicting CsTi_(3)Bi_(5) is missing and should be added,along with Ref.[3](originally Ref.[28]),to the introduction section.
High temperature superconductivity in cuprates is realized by doping the Mott insulator with charge carriers.A central issue is how such an insulating state can evolve into a conducting or superconducting state when c...High temperature superconductivity in cuprates is realized by doping the Mott insulator with charge carriers.A central issue is how such an insulating state can evolve into a conducting or superconducting state when charge carriers are introduced.Here,by in situ vacuum annealing and Rb deposition on the Bi2Sr2Ca0.6Dy0.4Cu2O8+δ(Bi2212)sample surface to push its doping level continuously from deeply underdoped(Tc=25K,doping level p^0.066)to the near-zero doping parent Mott insulator,angle-resolved photoemission spectroscopy measurements are carried out to observe the detailed electronic structure evolution in the lightly hole-doped region for the first time.Our results indicate that the chemical potential lies at about l eV above the charge transfer band for the parent state at zero doping,which is quite close to the upper Hubbard band.With increasing hole doping,the chemical potential moves continuously towards the charge transfer band and the band structure evolution exhibits a rigid band shift-like behavior.When the chemical potential approaches the charge transfer band at a doping level of^0.05,the nodal spectral weight near the Fermi level increases,followed by the emergence of the coherent quasiparticle peak and the insulator-superconductor transition.Our observations provide key insights in understanding the insulator-superconductor transition in doping the parent cuprate compound and for establishing related theories.展开更多
High resolution angle resolved photoemission measurements and band structure calculations are carried out to study the electronic structure of BaMnSb_(2). All the observed bands are nearly linear that extend to a wide...High resolution angle resolved photoemission measurements and band structure calculations are carried out to study the electronic structure of BaMnSb_(2). All the observed bands are nearly linear that extend to a wide energy range. The measured Fermi surface mainly consists of one hole pocket around Γ and a strong spot at Y which are formed from the crossing points of the linear bands. The measured electronic structure of BaMnSb_(2) is unusual and deviates strongly from the band structure calculations. These results will stimulate further efforts to theoretically understand the electronic structure of BaMnSb_(2) and search for novel properties in this Dirac material.展开更多
Atherosclerosis is an inflammatory disease that may cause severe heart disease and stroke.Current pharmacotherapy for atherosclerosis shows limited benefits.In the progression of atherosclerosis,monocyte adhesions and...Atherosclerosis is an inflammatory disease that may cause severe heart disease and stroke.Current pharmacotherapy for atherosclerosis shows limited benefits.In the progression of atherosclerosis,monocyte adhesions and inflammatory macrophages play vital roles.However,precise regulations of inflammatory immune microenvironments in pathological tissues remain challenging.Here,we report an atherosclerotic plaque-targeted selenopeptide nanomedicine for inhibiting atherosclerosis progression by reducing monocyte adhesions and inflammation of macrophages.The targeted nanomedicine has 2.2-fold enhancement in atherosclerotic lesion accumulation.The oxidation-responsibility of selenopeptide enables eliminations of reactive oxygen species and specific release of anti-inflammatory drugs,thereby reducing inflammation responses of macrophages.Notably,we find the oxidative metabolite of selenopeptide,octadecyl selenite,can bind to P-selectin in a high affinity with a dissociation constant of 1.5μM.This in situ generated active seleno-species further inhibit monocyte adhesions for anti-inflammation in synergy.With local regulations of monocyte adhesions and inflammations,the selenopeptide nanomedicine achieves 2.6-fold improvement in atherosclerotic plaque inhibition compared with simvastatin in the atherosclerosis mouse model.Meanwhile,the selenopeptide nanomedicine also displays excellent biological safety in both mice and rhesus monkeys.This study provides a safe and effective platform for regulating inflammatory immune microenvironments for inflammatory diseases such as atherosclerosis.展开更多
Oxidative stress and inflammation are central pathophysiological processes in a traumatic spinal cord injury(SCI).Antioxidant therapies that reduce the reactive oxygen and nitrogen species(RONS)overgeneration and infl...Oxidative stress and inflammation are central pathophysiological processes in a traumatic spinal cord injury(SCI).Antioxidant therapies that reduce the reactive oxygen and nitrogen species(RONS)overgeneration and inflammation are proved promising for improving the outcomes.However,efficient and long-lasting antioxidant therapy to eliminate multiple RONS with effective neuroprotection remains challenging.Here,a single-atom cobalt nanozyme(Co-SAzyme)with a hollow structure was reported to reduce the RONS and inflammation in the secondary injury of SCI.Among SAzymes featuring different single metal-N sites(e.g.,Mn,Fe,Co,Ni,and Cu),this Co-SAzyme showed a versatile property to eliminate hydrogen peroxide(H_(2)O_(2)),superoxide anion(O_(2)·^(-)),hydroxyl radical(·OH),nitric oxide(·NO),and peroxynitrite(ONOO^(-))that overexpressed in the early stage of SCI.The porous hollow structure also allowed the encapsulation and sustained release of minocycline for neuroprotection in synergy.In vitro results showed that the Co-SAzyme reduced the apoptosis and pro-inflammatory cytokine levels of microglial cells under oxidative stress.In addition,the Co-SAzyme combined with minocycline achieved remarkable improved functional recovery and neural repairs in the SCI-rat model.展开更多
Topological states of matter possess bulk electronic structures categorized by topological invariants and edge/surface states due to the bulk-boundary correspondence. Topological materials hold great potential in the ...Topological states of matter possess bulk electronic structures categorized by topological invariants and edge/surface states due to the bulk-boundary correspondence. Topological materials hold great potential in the development of dissipationless spintronics, information storage and quantum computation, particularly if combined with magnetic order intrinsically or extrinsically. Here, we review the recent progress in the exploration of intrinsic magnetic topological materials, including but not limited to magnetic topological insulators, magnetic topological metals, and magnetic Weyl semimetals. We pay special attention to their characteristic band features such as the gap of topological surface state, gapped Dirac cone induced by magnetization (either bulk or surface), Weyl nodal point/line and Fermi arc, as well as the exotic transport responses resulting from such band features. We conclude with a brief envision for experimental explorations of new physics or effects by incorporating other orders in intrinsic magnetic topological materials.展开更多
The mono layer WSe2 is in teresting and important for future application in nanoelectronics,spintronics and valleytronics devices,because it has the largest spin splitting and Ion gest valley coherence time among all ...The mono layer WSe2 is in teresting and important for future application in nanoelectronics,spintronics and valleytronics devices,because it has the largest spin splitting and Ion gest valley coherence time among all the known monolayer transition-metal dichalcogenides(TMDs).Toobtain the large-area monolayer TMDs'crystal is the first step to manu facture scalable and high-performance electronic devices.In this letter,we have successfully fabricated millimeter-sized mono layer WSe2 single crystals with very high quality,based on our improved mecha nicalexfoliation method.With such superior samples,using standard high resolution angle-resolved photoemission spectroscopy,we didcomprehe nsive electronic band structure measurements on our mono layer WSe2.The overall band features point it to be a 1.2 eV direct bandgap semico nductor.Its spin splitting of the valence band at K point is found as 460 meV,which is 30 meV less than the corresponding band splitting in its bulk counterpart.The effective hole masses of valence bands are determined as 2.344 me atГ,and 0.529 me as well as 0.532 meat K for the upper and lower branch of splitting ban ds,respectively.And screening effect from substrate is shown to substa ntially impact onthe electronic properties.Our results provide importa nt insights into band structure engineering in mono layer TMDs.Our mono layer WSe2 crystals may constitute a valuable device platform.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12488201,12374066,12074411,and 12374154)the National Key Research and Development Program of China(Grant Nos.2021YFA1401800,2022YFA1604200,2022YFA1403900,and 2023YFA1406000)+3 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant Nos.XDB25000000 and XDB33000000)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301800)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.Y2021006)the Synergetic Extreme Condition User Facility(SECUF)。
文摘In high temperature cuprate superconductors,it was found that the superfluid density decreases with the increase of hole doping.One natural question is whether there exists normal fluid in the superconducting state in the overdoped region.In this paper,we have carried out high-resolution ultra-low temperature laser-based angle-resolved photoemission measurements on a heavily overdoped Bi2212 sample with a T_(c) of 48 K.We find that this heavily overdoped Bi2212 remains in the strong coupling regime with 2Δ_(0)/(k_(B)T_(c))=5.8.The single-particle scattering rate is very small along the nodal direction(~5 meV) and increases as the momentum moves from the nodal to the antinodal regions.A hard superconducting gap opening is observed near the antinodal region with the spectral weight at the Fermi level fully suppressed to zero.The normal fluid is found to be negligibly small in the superconducting state of this heavily overdoped Bi2212.These results provide key information to understand the high T_(c) mechanism in the cuprate superconductors.
基金Project supported by the National Key Research and Development Program of China (Grant No. 2022YFA1403700)the National Natural Science Foundation of China (Grant No. 12074163)+2 种基金the Basic and Applied Basic Research Foundation of Guangdong Province, China (Grants Nos. 2022B1515020046, 2022B1515130005, and 2021B1515130007)the Innovative and Entrepreneurial Research Team Program of Guangdong Province, China (Grant Nos. 2019ZT08C044)Shenzhen Science and Technology Program (Grant No. KQTD20190929173815000)
文摘Magnetic topological states of matter provide a fertile playground for emerging topological physics and phenomena.The current main focus is on materials whose magnetism stems from 3d magnetic transition elements,e.g.,MnBi_(2)Te_(4),Fe_(3)Sn_(2),and Co_(3)Sn_(2)S_(2).In contrast,topological materials with the magnetism from rare earth elements remain largely unexplored.Here we report rare earth antiferromagnet GdAuAl_(4)Ge_(2)as a candidate magnetic topological metal.Angle resolved photoemission spectroscopy(ARPES)and first-principles calculations have revealed multiple bulk bands crossing the Fermi level and pairs of low energy surface states.According to the parity and Wannier charge center analyses,these bulk bands possess nontrivial Z2 topology,establishing a strong topological insulator state in the nonmagnetic phase.Furthermore,the surface band pairs exhibit strong termination dependence which provides insight into their origin.Our results suggest GdAuAl_(4)Ge_(2)as a rare earth platform to explore the interplay between band topology,magnetism and f electron correlation,calling for further study targeting on its magnetic structure,magnetic topology state,transport behavior,and microscopic properties.
基金the National Key R&D Program of China(Grant No.2022YFA1403700)the National Natural Science Foundation of China(Grant Nos.12074163 and 12004030)+5 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2022B1515020046,2022B1515130005,2021B1515130007,and 2020B1515120100)the Guangdong Innovative and Entrepreneurial Research Team Program(Grant Nos.2017ZT07C062 and 2019ZT08C044)the Shenzhen Science and Technology Program(Grant No.KQTD20190929173815000)Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices(Grant No.ZDSYS20190902092905285)the Shenzhen Fundamental Research Program(Grant No.JCYJ20220818100405013)China Postdoctoral Science Foundation(Grant No.2020M682780 and 2022M711495)。
文摘The simple kagome-lattice band structure possesses Dirac cones,flat band,and saddle point with van Hove singularities in the electronic density of states,facilitating the emergence of various electronic orders.Here we report a titanium-based kagome metal CsTi_(3)Bi_(5)where titanium atoms form a kagome network,resembling its isostructural compound CsV_3Sb_5.Thermodynamic properties including the magnetization,resistance,and heat capacity reveal the conventional Fermi liquid behavior in the kagome metal CsTi_(3)Bi_(5)and no signature of superconducting or charge density wave(CDW)transition anomaly down to 85 m K.Systematic angle-resolved photoemission spectroscopy measurements reveal multiple bands crossing the Fermi level,consistent with the first-principles calculations.The flat band formed by the destructive interference of hopping in the kagome lattice is observed directly.Compared to Cs V_(3)Sb_(5),the van Hove singularities are pushed far away above the Fermi level in CsTi_(3)Bi_(5),in line with the absence of CDW.Furthermore,the first-principles calculations identify the nontrivial Z_(2)topological properties for those bands crossing the Fermi level,accompanied by several local band inversions.Our results suppose CsTi_(3)Bi_(5)as a complementary platform to explore the superconductivity and nontrivial band topology.
文摘In our most recently published article,[1]an important reference[2]predicting CsTi_(3)Bi_(5) is missing and should be added,along with Ref.[3](originally Ref.[28]),to the introduction section.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11888101,11922414,and 11534007)the National Key Research and Development Program of China(Grant Nos.2016YFA0300300 and 2017YFA0302900)+2 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)the Youth Innovation Promotion Association of CAS(Grant No.2017013)the Research Program of Beijing Academy of Quantum Information Sciences(Grant No.Y18G06).
文摘High temperature superconductivity in cuprates is realized by doping the Mott insulator with charge carriers.A central issue is how such an insulating state can evolve into a conducting or superconducting state when charge carriers are introduced.Here,by in situ vacuum annealing and Rb deposition on the Bi2Sr2Ca0.6Dy0.4Cu2O8+δ(Bi2212)sample surface to push its doping level continuously from deeply underdoped(Tc=25K,doping level p^0.066)to the near-zero doping parent Mott insulator,angle-resolved photoemission spectroscopy measurements are carried out to observe the detailed electronic structure evolution in the lightly hole-doped region for the first time.Our results indicate that the chemical potential lies at about l eV above the charge transfer band for the parent state at zero doping,which is quite close to the upper Hubbard band.With increasing hole doping,the chemical potential moves continuously towards the charge transfer band and the band structure evolution exhibits a rigid band shift-like behavior.When the chemical potential approaches the charge transfer band at a doping level of^0.05,the nodal spectral weight near the Fermi level increases,followed by the emergence of the coherent quasiparticle peak and the insulator-superconductor transition.Our observations provide key insights in understanding the insulator-superconductor transition in doping the parent cuprate compound and for establishing related theories.
基金supported by the National Key Research and Development Program of China (Grant Nos. 2016YFA0300600, 2018YFA0305602, 2016YFA0300300,2017YFA0302900)the National Natural Science Foundation of China (Grant Nos. 11974404, 11888101, 11922414, and 11404175)+8 种基金the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant Nos. XDB33000000 and XDB25000000)the Youth Innovation Promotion Association of CAS (Grant No. 2017013)the Natural Science Foundation of Henan Province,China (Grant Nos. 182300410274 and 202300410296)The theoretical calculations are supported by the National Natural Science Foundation of China (Grant Nos. 11674369, 11865019, and 11925408)the Beijing Natural Science Foundation,China (Grant No. Z180008)Beijing Municipal Science and Technology Commission,China (Grant No. Z191100007219013)the National Key Research and Development Program of China (Grant Nos. 2016YFA0300600 and 2018YFA0305700)the K. C. Wong Education Foundation (Grant No. GJTD-2018-01)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB33000000)。
文摘High resolution angle resolved photoemission measurements and band structure calculations are carried out to study the electronic structure of BaMnSb_(2). All the observed bands are nearly linear that extend to a wide energy range. The measured Fermi surface mainly consists of one hole pocket around Γ and a strong spot at Y which are formed from the crossing points of the linear bands. The measured electronic structure of BaMnSb_(2) is unusual and deviates strongly from the band structure calculations. These results will stimulate further efforts to theoretically understand the electronic structure of BaMnSb_(2) and search for novel properties in this Dirac material.
基金financially supported by the National Natural Science Foundation of China(Nos.51890892,22175048,22007024,and 21805058)National Key R&D Program of China(No.2018YFE0205400)Beijing Natural Science Foundation(No.2232072).
文摘Atherosclerosis is an inflammatory disease that may cause severe heart disease and stroke.Current pharmacotherapy for atherosclerosis shows limited benefits.In the progression of atherosclerosis,monocyte adhesions and inflammatory macrophages play vital roles.However,precise regulations of inflammatory immune microenvironments in pathological tissues remain challenging.Here,we report an atherosclerotic plaque-targeted selenopeptide nanomedicine for inhibiting atherosclerosis progression by reducing monocyte adhesions and inflammation of macrophages.The targeted nanomedicine has 2.2-fold enhancement in atherosclerotic lesion accumulation.The oxidation-responsibility of selenopeptide enables eliminations of reactive oxygen species and specific release of anti-inflammatory drugs,thereby reducing inflammation responses of macrophages.Notably,we find the oxidative metabolite of selenopeptide,octadecyl selenite,can bind to P-selectin in a high affinity with a dissociation constant of 1.5μM.This in situ generated active seleno-species further inhibit monocyte adhesions for anti-inflammation in synergy.With local regulations of monocyte adhesions and inflammations,the selenopeptide nanomedicine achieves 2.6-fold improvement in atherosclerotic plaque inhibition compared with simvastatin in the atherosclerosis mouse model.Meanwhile,the selenopeptide nanomedicine also displays excellent biological safety in both mice and rhesus monkeys.This study provides a safe and effective platform for regulating inflammatory immune microenvironments for inflammatory diseases such as atherosclerosis.
基金This research was financially supported by the National Natural Science Foundation of China(Nos.22175048,22005027,and 51890892)Tianjin Health Commission(No.ZC20175).
文摘Oxidative stress and inflammation are central pathophysiological processes in a traumatic spinal cord injury(SCI).Antioxidant therapies that reduce the reactive oxygen and nitrogen species(RONS)overgeneration and inflammation are proved promising for improving the outcomes.However,efficient and long-lasting antioxidant therapy to eliminate multiple RONS with effective neuroprotection remains challenging.Here,a single-atom cobalt nanozyme(Co-SAzyme)with a hollow structure was reported to reduce the RONS and inflammation in the secondary injury of SCI.Among SAzymes featuring different single metal-N sites(e.g.,Mn,Fe,Co,Ni,and Cu),this Co-SAzyme showed a versatile property to eliminate hydrogen peroxide(H_(2)O_(2)),superoxide anion(O_(2)·^(-)),hydroxyl radical(·OH),nitric oxide(·NO),and peroxynitrite(ONOO^(-))that overexpressed in the early stage of SCI.The porous hollow structure also allowed the encapsulation and sustained release of minocycline for neuroprotection in synergy.In vitro results showed that the Co-SAzyme reduced the apoptosis and pro-inflammatory cytokine levels of microglial cells under oxidative stress.In addition,the Co-SAzyme combined with minocycline achieved remarkable improved functional recovery and neural repairs in the SCI-rat model.
基金This work was supported by the National Key R&D Program of China(Grant Nos.2022YFA1403700 and 2020YFA0308900)the National Natural Science Foundation of China(NSFC)(Grant Nos.12074163,12074161,and 11504159)+3 种基金NSFC Guangdong(No.2016A030313650)Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2022B1515020046,2022B1515130005 and 2021B1515130007)the Guangdong Innovative and Entrepreneurial Research Team Program(Grant Nos.2019ZT08C044 and 2016ZT06D348)Shenzhen Science and Technology Program(Grant No.KQTD20190929173815000).
文摘Topological states of matter possess bulk electronic structures categorized by topological invariants and edge/surface states due to the bulk-boundary correspondence. Topological materials hold great potential in the development of dissipationless spintronics, information storage and quantum computation, particularly if combined with magnetic order intrinsically or extrinsically. Here, we review the recent progress in the exploration of intrinsic magnetic topological materials, including but not limited to magnetic topological insulators, magnetic topological metals, and magnetic Weyl semimetals. We pay special attention to their characteristic band features such as the gap of topological surface state, gapped Dirac cone induced by magnetization (either bulk or surface), Weyl nodal point/line and Fermi arc, as well as the exotic transport responses resulting from such band features. We conclude with a brief envision for experimental explorations of new physics or effects by incorporating other orders in intrinsic magnetic topological materials.
基金This work is supported by the National Science Foundation of China(Nos.11574367 and 11874405)the National Key Research and Development Program of China(Nos.2016YFA0300600,2018YFA0704200,and 2019YFA0308000)the Youth Innovation Promotion Association of CAS(Nos.2017013 and 2019007).
文摘The mono layer WSe2 is in teresting and important for future application in nanoelectronics,spintronics and valleytronics devices,because it has the largest spin splitting and Ion gest valley coherence time among all the known monolayer transition-metal dichalcogenides(TMDs).Toobtain the large-area monolayer TMDs'crystal is the first step to manu facture scalable and high-performance electronic devices.In this letter,we have successfully fabricated millimeter-sized mono layer WSe2 single crystals with very high quality,based on our improved mecha nicalexfoliation method.With such superior samples,using standard high resolution angle-resolved photoemission spectroscopy,we didcomprehe nsive electronic band structure measurements on our mono layer WSe2.The overall band features point it to be a 1.2 eV direct bandgap semico nductor.Its spin splitting of the valence band at K point is found as 460 meV,which is 30 meV less than the corresponding band splitting in its bulk counterpart.The effective hole masses of valence bands are determined as 2.344 me atГ,and 0.529 me as well as 0.532 meat K for the upper and lower branch of splitting ban ds,respectively.And screening effect from substrate is shown to substa ntially impact onthe electronic properties.Our results provide importa nt insights into band structure engineering in mono layer TMDs.Our mono layer WSe2 crystals may constitute a valuable device platform.
