We explore the excitonic effects in chiral graphene nanoribbons (cGNRs), whose edges are composed alternatively of armchair-edged and zigzag-edged segments. For cGNRs dominated by armchair edges, their energy gaps and...We explore the excitonic effects in chiral graphene nanoribbons (cGNRs), whose edges are composed alternatively of armchair-edged and zigzag-edged segments. For cGNRs dominated by armchair edges, their energy gaps and exciton energies decrease with increasing chirality angles, and they, as functions of widths, oscillate with the period of three, while the exciton binding energies do not have such distinct oscillation. On the other hand, for cGNRs dominated by zigzag edges, all the energy gaps, exciton energies, and exciton binding energies show oscillation properties with their widths, due to the interactions between the edge states localized at the opposite zigzag edges. In addition, the triplet excitons are energy degenerate when the electrons are spin-unpolarized, while the degeneracy split when the electrons are spin-polarized. All the studied cGNRs show strong excitonic effects with the exciton binding energies of hundreds of meV.展开更多
The electronic structure of semiconductor materials governs the law of electron motion,which profoundly affects the properties such as conductivity and photoelectric conversion.Photo-responsive single-molecule junctio...The electronic structure of semiconductor materials governs the law of electron motion,which profoundly affects the properties such as conductivity and photoelectric conversion.Photo-responsive single-molecule junction technology provides insights into the electronic structure of photogenerated substances at the molecular scale,enabling the characterization of dynamic processes such as charge separation and energy transfer.These processes involve the unique quantum state known as the "exciton".The electrical characterization technique based on single molecule break junction facilities direct measurement of the photoelectric response of molecules at nanometer and subnanometer scale.This study reviews recent research progress of exciton effects and the characterization of optoelectronic phenomena.The mechanisms of exciton effects in three key optoelectronic phenomena—photoconductivity,photovoltaic s,and photoluminescence—are discussed.Furthermore,advanced spectral characterization techniques applied to the in-situ monitoring of single-molecule optoelectronic devices are highlighted.These include Raman spectroscopy with various enhancements,inelastic electron tunneling spectroscopy,and ultrafast spectroscopy with high resolution.展开更多
The exciton states of semiconducting carbon nanotubes are calculated by a tight-binding model supplemented by Coulomb interactions under the combined effect of uniaxial strain and magnetic field. It is found that the ...The exciton states of semiconducting carbon nanotubes are calculated by a tight-binding model supplemented by Coulomb interactions under the combined effect of uniaxial strain and magnetic field. It is found that the excitation energies and absorption spectra of zigzag tubes（11,0） and（10,0） show opposite trends with the strain under the action of the magnetic field. For the（11,0） tube, the excitation energy decreases with the increasing uniaxial strain, with a splitting appearing in the absorption spectra. For the（10,0） tube, the variation trend firstly increases and then decreases, with a reversal point appearing in the absorption spectra. More interesting,at the reversal point the intensity of optical absorption is the largest because of the degeneracy of the two bands nearest to the Fermi Level, which is expected to be observed in the future experiment. The similar variation trend is also exhibited in the binding energy for the two kinds of semiconducting tubes.展开更多
Incorporating low-dimensionalization technologies effectively tackle the challenge of inadequate long-term stability in hybrid halide perovskites,however their wide bandgap and strong quantum well confinement remain s...Incorporating low-dimensionalization technologies effectively tackle the challenge of inadequate long-term stability in hybrid halide perovskites,however their wide bandgap and strong quantum well confinement remain substantial obstacle for various optoelectronic applications.Addressing these issues without compromising longterm stability has emerged as a pivotal focus in materials science,in particular exploring the effects of the functional groups within spacer cations.Our simulations reveal that the robustπ-πstacking interactions involving PEA^(+)and the strong hydrogen bonding interactions between PEA^(+)and MX^(4-)_(6)contribute to narrowing the electronic bandgap in 2D monolayer PEA_(2)MX_(4)(e.g.2D monolayer PEA_(2)SnI_(4):1.34 eV)for reasonable visible-light absorption while simultaneously ensuring their favorable long-term stability.Moreover,the delocalized orbitals and relatively high dielectric constants in PEA^(+),attributed to the conjugated benzene ring,has been observed to weaken the potential barrier,exciton binding effect and quantum well confinement in 2D monolayer PEA2MX4,thus facilitating photogenerated electron-hole separations and out-of-plane carrier transport.The impact of spacer cations on the optoelectronic and transport properties of 2D monolayer perovskites highlights the critical role of meticulously chosen and well-designed spacer cations,especially functional groups,in shaping their photophysical properties and ensuring long-term stability even under extremely operating conditions.展开更多
TiSe_(2)is a narrow-gap insulator with a rich array of unique properties.In addition to being a superconductor under certain modifications,it is commonly thought to be a rare realisation of an excitonic insulator.Belo...TiSe_(2)is a narrow-gap insulator with a rich array of unique properties.In addition to being a superconductor under certain modifications,it is commonly thought to be a rare realisation of an excitonic insulator.Below 200 K,TiSe_(2)undergoes a transition from a high-symmetry(P3^(-)m1)phase to a low-symmetry(P3^(-)c1)charge density wave(CDW).Here we establish that it is indeed an insulator in both P3^(-)m1 and P3^(-)c1 phases.However,the insulating state is driven not by excitonic effects but by symmetry-breaking.In theCDWphase it is static.At high temperature,thermally driven instantaneous deviations from P3^(-)m1 break the symmetry on the characteristic time scale of a phonon.Even though the time-averaged lattice structure assumes P3^(-)m1 symmetry,the time-averaged energy band structure is closer to the CDW phase–a rare instance of a metal-insulator transition induced by dynamical symmetry breaking.We establish these conclusions from quasiparticle self-consistent GW(QSGW)and many-body calculations(QSG b W),incombination withmolecular dynamics simulations to capture the effects of thermal disorder.The many-body theory includes explicitly ladder diagrams in the polarizability,which incorporates excitonic effects in an ab initio manner.We find that the excitonic modification to the potential is weak,ruling out the possibility that TiSe_(2)is an excitonic insulator.展开更多
Excitons have significant impacts on the properties of semiconductors.They exhibit significantly different properties when a direct semiconductor turns in to an indirect one by doping.Huybrecht variational method is a...Excitons have significant impacts on the properties of semiconductors.They exhibit significantly different properties when a direct semiconductor turns in to an indirect one by doping.Huybrecht variational method is also found to influence the study of exciton ground state energy and ground state binding energy in Al_(x)Ga_(1−x)As semiconductor spherical quantum dots.The Al_(x)Ga_(1−x)As is considered to be a direct semiconductor at AI concentration below 0.45,and an indirect one at the concentration above 0.45.With regards to the former,the ground state binding energy increases and decreases with AI concentration and eigenfrequency,respectively;however,while the ground state energy increases with AI concentration,it is marginally influenced by eigenfrequency.On the other hand,considering the latter,while the ground state binding energy increases with AI concentration,it decreases with eigenfrequency;nevertheless,the ground state energy increases both with AI concentration and eigenfrequency.Hence,for the better practical performance of the semiconductors,the properties of the excitons are suggested to vary by adjusting AI concentration and eigenfrequency.展开更多
Strong geometrical confinement and reduced dielectric screening of two-dimensional(2D)materials leads to strong Coulomb interaction and eventually give rise to extraordinary excitonic effects,which dominates the optic...Strong geometrical confinement and reduced dielectric screening of two-dimensional(2D)materials leads to strong Coulomb interaction and eventually give rise to extraordinary excitonic effects,which dominates the optical and optoelectronic properties.For nonlinear 2D photonic or optoelectronic applications,excitonic effects have been proved effective to tune the light-matter interaction strength.However,the modulation of excitonic effects on the other aspect of nonlinear response,i.e.,polarization dependence,has not been fully explored yet.Here we report the first systemic study on the modulation of excitonic effects on the polarization dependence of second and third harmonic generation(SHG and THG)in strained monolayer WS2 by varying excitation wavelength.We demonstrated that polarization-dependent THG patterns undergo a giant evolution near two-photon excitonic resonance,where the long-axis of the parallel component(originally parallel to the strain direction)has a 90°flip when the excitation wavelength increases.In striking contrast,no apparent variation of polarization-dependent SHG patterns occurs at either two-or three-photon excitonic resonance conditions.Our results open a new avenue to modulate the anisotropic nonlinear optical response of 2D materials through effective control of excitonic resonance states,and thus open opportunity for new designs and applications in nonlinear optoelectronic 2D devices.展开更多
Taking into account anisotropy, nonparabolicity of the conduction band, and geometrical confinement, we discuss the heavy-hole excitonic states in a strained GaxIn1-xAs/GaAs quantum dot for various Ga alloy contents. ...Taking into account anisotropy, nonparabolicity of the conduction band, and geometrical confinement, we discuss the heavy-hole excitonic states in a strained GaxIn1-xAs/GaAs quantum dot for various Ga alloy contents. The strained quantum dot is considered as a spherical InAs dot surrounded by a GaAs barrier material. The dependence of the effective excitonic g-factor as a function of dot radius and Ga ion content is numerically measured. Interband optical energy with and without the parabolic effect is computed using structural confinement. The interband matrix element for different Ga concentrations is also calculated. The oscillator strength of interband transitions on the dot radius is studied at different Ga concentrations in the GaxIn1-xAs/GaAs quantum dot. Heavy-hole excitonic absorption spectra are recorded for various Ga alloy contents in the GaxIn1-xAs/GaAs quantum dot. Results show that oscillator strength diminishes when dot size decreases because of the dominance of the quantum size effect. Furthermore, exchange enhancement and exchange sDlitting increase as exciton confinement inereases.展开更多
It is well-known that exciton effects are determinant to understanding the optical absorption spectrum of low-dimensional materials.However,the role of excitons in nonlinear optical responses has been much less invest...It is well-known that exciton effects are determinant to understanding the optical absorption spectrum of low-dimensional materials.However,the role of excitons in nonlinear optical responses has been much less investigated at the experimental level.Additionally,computational methods to calculate nonlinear conductivities in real materials are still not widespread,particularly taking into account excitonic interactions.We present a methodology to calculate the excitonic second-order optical responses in 2D materials relying on:(i)ab initio tight-binding Hamiltonians obtained by Wannier interpolation and(ii)solving the Bethe-Salpeter equation with effective electron-hole interactions.Here,in particular,we explore the role of excitons in the shift current of monolayer materials.Focusing on MoS_(2)and GeS monolayer systems,our results show that 2p-like excitons,which are dark in the linear response regime,yield a contribution to the photocurrent comparable to that of 1s-like excitons.Under radiation with intensity~104W/cm2,the excitonic theory predicts in-gap photogalvanic currents of almost~10 nA in sufficiently clean samples,which is typically one order of magnitude higher than the value predicted by independent-particle theory near the band edge.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
基金Supported by the National Key Scientific Research Projects of China under Grant No 2015CB932400the National Natural Science Foundation of China under Grant Nos 11504158,61474059,and U1432129+1 种基金the Program for New Century Excellent Talents in University of Ministry of Education of China under Grant No NCET-11-1003the Jiangxi Provincial'Ganpo Talentes 555Projects'
文摘We explore the excitonic effects in chiral graphene nanoribbons (cGNRs), whose edges are composed alternatively of armchair-edged and zigzag-edged segments. For cGNRs dominated by armchair edges, their energy gaps and exciton energies decrease with increasing chirality angles, and they, as functions of widths, oscillate with the period of three, while the exciton binding energies do not have such distinct oscillation. On the other hand, for cGNRs dominated by zigzag edges, all the energy gaps, exciton energies, and exciton binding energies show oscillation properties with their widths, due to the interactions between the edge states localized at the opposite zigzag edges. In addition, the triplet excitons are energy degenerate when the electrons are spin-unpolarized, while the degeneracy split when the electrons are spin-polarized. All the studied cGNRs show strong excitonic effects with the exciton binding energies of hundreds of meV.
基金financially supported by the Program of Higher-Level Talents of IMU(No.21300-5223748)the National Natural Science Foundation of China(Nos.22103065 and 21661024)
文摘The electronic structure of semiconductor materials governs the law of electron motion,which profoundly affects the properties such as conductivity and photoelectric conversion.Photo-responsive single-molecule junction technology provides insights into the electronic structure of photogenerated substances at the molecular scale,enabling the characterization of dynamic processes such as charge separation and energy transfer.These processes involve the unique quantum state known as the "exciton".The electrical characterization technique based on single molecule break junction facilities direct measurement of the photoelectric response of molecules at nanometer and subnanometer scale.This study reviews recent research progress of exciton effects and the characterization of optoelectronic phenomena.The mechanisms of exciton effects in three key optoelectronic phenomena—photoconductivity,photovoltaic s,and photoluminescence—are discussed.Furthermore,advanced spectral characterization techniques applied to the in-situ monitoring of single-molecule optoelectronic devices are highlighted.These include Raman spectroscopy with various enhancements,inelastic electron tunneling spectroscopy,and ultrafast spectroscopy with high resolution.
基金Supported by the National Natural Science Foundation of China under Grant No 11304378the Fundamental Research Funds for the Central Universities under Grant No 2017XKQY093
文摘The exciton states of semiconducting carbon nanotubes are calculated by a tight-binding model supplemented by Coulomb interactions under the combined effect of uniaxial strain and magnetic field. It is found that the excitation energies and absorption spectra of zigzag tubes（11,0） and（10,0） show opposite trends with the strain under the action of the magnetic field. For the（11,0） tube, the excitation energy decreases with the increasing uniaxial strain, with a splitting appearing in the absorption spectra. For the（10,0） tube, the variation trend firstly increases and then decreases, with a reversal point appearing in the absorption spectra. More interesting,at the reversal point the intensity of optical absorption is the largest because of the degeneracy of the two bands nearest to the Fermi Level, which is expected to be observed in the future experiment. The similar variation trend is also exhibited in the binding energy for the two kinds of semiconducting tubes.
基金supported by the National Natural Science Foundation of China(Grant Nos.22103012,22173104)Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(FJOEL,Grant No.2021ZR109)the Future-prospective and Stride-across Programs of Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences(Grant No.CXZX-2022-GH02)。
文摘Incorporating low-dimensionalization technologies effectively tackle the challenge of inadequate long-term stability in hybrid halide perovskites,however their wide bandgap and strong quantum well confinement remain substantial obstacle for various optoelectronic applications.Addressing these issues without compromising longterm stability has emerged as a pivotal focus in materials science,in particular exploring the effects of the functional groups within spacer cations.Our simulations reveal that the robustπ-πstacking interactions involving PEA^(+)and the strong hydrogen bonding interactions between PEA^(+)and MX^(4-)_(6)contribute to narrowing the electronic bandgap in 2D monolayer PEA_(2)MX_(4)(e.g.2D monolayer PEA_(2)SnI_(4):1.34 eV)for reasonable visible-light absorption while simultaneously ensuring their favorable long-term stability.Moreover,the delocalized orbitals and relatively high dielectric constants in PEA^(+),attributed to the conjugated benzene ring,has been observed to weaken the potential barrier,exciton binding effect and quantum well confinement in 2D monolayer PEA2MX4,thus facilitating photogenerated electron-hole separations and out-of-plane carrier transport.The impact of spacer cations on the optoelectronic and transport properties of 2D monolayer perovskites highlights the critical role of meticulously chosen and well-designed spacer cations,especially functional groups,in shaping their photophysical properties and ensuring long-term stability even under extremely operating conditions.
基金the National Renewable Energy Laboratory for the U.S.Department of Energy(DOE)under Contract No.DE-AC36-08GO28308 Funding was provided by Office of Science,Basic Energy Sciences,Division of MaterialsWe acknowledge the use of the National Energy Research Scientific Computing Center,under Contract No.DE-AC02-05CH11231 using NERSC award BES-ERCAP0021783we also acknowledge that a portion of the research was performed using computational resources sponsored by the Department of Energy’s Office of Energy Efficiency and Renewable Energy and located at the National Renewable Energy Laboratory,and computational resources provided by the Oakridge leadership Computing Facility.The views expressed in the article do not necessarily represent the views of the DOE or the U.S.Government.The U.S.Government retains and the publisher,by accepting the article for publication,acknowledges that the U.S.Government retains a nonexclusive,paid-up,irrevocable,worldwide license to publish or reproduce the published form of this work,or allow others to do so,for U.S.Government purposes.
文摘TiSe_(2)is a narrow-gap insulator with a rich array of unique properties.In addition to being a superconductor under certain modifications,it is commonly thought to be a rare realisation of an excitonic insulator.Below 200 K,TiSe_(2)undergoes a transition from a high-symmetry(P3^(-)m1)phase to a low-symmetry(P3^(-)c1)charge density wave(CDW).Here we establish that it is indeed an insulator in both P3^(-)m1 and P3^(-)c1 phases.However,the insulating state is driven not by excitonic effects but by symmetry-breaking.In theCDWphase it is static.At high temperature,thermally driven instantaneous deviations from P3^(-)m1 break the symmetry on the characteristic time scale of a phonon.Even though the time-averaged lattice structure assumes P3^(-)m1 symmetry,the time-averaged energy band structure is closer to the CDW phase–a rare instance of a metal-insulator transition induced by dynamical symmetry breaking.We establish these conclusions from quasiparticle self-consistent GW(QSGW)and many-body calculations(QSG b W),incombination withmolecular dynamics simulations to capture the effects of thermal disorder.The many-body theory includes explicitly ladder diagrams in the polarizability,which incorporates excitonic effects in an ab initio manner.We find that the excitonic modification to the potential is weak,ruling out the possibility that TiSe_(2)is an excitonic insulator.
基金supported by the National Natural Science Foundation of China(Nos.12164032 and 11964026)the Natural Science Foundation of Inner Mongolia(No.2019MS01010)+3 种基金Scientific Research Projects in Colleges and Universities in Inner Mongolia(No.NJZZ19145)Graduate Science Innovative Research Projects(No.S20210281Z)the Natural Science Foundation of Inner Mongolia(No.2022MS01014)Doctor Research Start-up Fund of Inner Mongolia Minzu University(No.BS625).
文摘Excitons have significant impacts on the properties of semiconductors.They exhibit significantly different properties when a direct semiconductor turns in to an indirect one by doping.Huybrecht variational method is also found to influence the study of exciton ground state energy and ground state binding energy in Al_(x)Ga_(1−x)As semiconductor spherical quantum dots.The Al_(x)Ga_(1−x)As is considered to be a direct semiconductor at AI concentration below 0.45,and an indirect one at the concentration above 0.45.With regards to the former,the ground state binding energy increases and decreases with AI concentration and eigenfrequency,respectively;however,while the ground state energy increases with AI concentration,it is marginally influenced by eigenfrequency.On the other hand,considering the latter,while the ground state binding energy increases with AI concentration,it decreases with eigenfrequency;nevertheless,the ground state energy increases both with AI concentration and eigenfrequency.Hence,for the better practical performance of the semiconductors,the properties of the excitons are suggested to vary by adjusting AI concentration and eigenfrequency.
基金This work was supported by The Key R&D Program of Guangdong Province(Nos.2019B010931001,2020B010189001,2018B010109009,and 2018B030327001)the National Natural Science Foundation of China(Nos.51991340 and 51991342)+7 种基金the National Key R&D Program of China(Nos.2016YFA0300903 and 2016YFA0300804)Beijing Natural Science Foundation(No.JQ19004)Beijing Excellent Talents Training Support(No.2017000026833ZK11)Beijing Municipal Science&Technology Commission(No.Z191100007219005)Beijing Graphene Innovation Program(No.Z181100004818003)Bureau of Industry and Information Technology of Shenzhen(Graphene platform 201901161512)Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06D348)the Science,Technology and Innovation Commission of Shenzhen Municipality(No.KYTDPT20181011104202253).
文摘Strong geometrical confinement and reduced dielectric screening of two-dimensional(2D)materials leads to strong Coulomb interaction and eventually give rise to extraordinary excitonic effects,which dominates the optical and optoelectronic properties.For nonlinear 2D photonic or optoelectronic applications,excitonic effects have been proved effective to tune the light-matter interaction strength.However,the modulation of excitonic effects on the other aspect of nonlinear response,i.e.,polarization dependence,has not been fully explored yet.Here we report the first systemic study on the modulation of excitonic effects on the polarization dependence of second and third harmonic generation(SHG and THG)in strained monolayer WS2 by varying excitation wavelength.We demonstrated that polarization-dependent THG patterns undergo a giant evolution near two-photon excitonic resonance,where the long-axis of the parallel component(originally parallel to the strain direction)has a 90°flip when the excitation wavelength increases.In striking contrast,no apparent variation of polarization-dependent SHG patterns occurs at either two-or three-photon excitonic resonance conditions.Our results open a new avenue to modulate the anisotropic nonlinear optical response of 2D materials through effective control of excitonic resonance states,and thus open opportunity for new designs and applications in nonlinear optoelectronic 2D devices.
文摘Taking into account anisotropy, nonparabolicity of the conduction band, and geometrical confinement, we discuss the heavy-hole excitonic states in a strained GaxIn1-xAs/GaAs quantum dot for various Ga alloy contents. The strained quantum dot is considered as a spherical InAs dot surrounded by a GaAs barrier material. The dependence of the effective excitonic g-factor as a function of dot radius and Ga ion content is numerically measured. Interband optical energy with and without the parabolic effect is computed using structural confinement. The interband matrix element for different Ga concentrations is also calculated. The oscillator strength of interband transitions on the dot radius is studied at different Ga concentrations in the GaxIn1-xAs/GaAs quantum dot. Heavy-hole excitonic absorption spectra are recorded for various Ga alloy contents in the GaxIn1-xAs/GaAs quantum dot. Results show that oscillator strength diminishes when dot size decreases because of the dominance of the quantum size effect. Furthermore, exchange enhancement and exchange sDlitting increase as exciton confinement inereases.
基金support from the Spanish MICINN(grants nos.PID2019-109539GB-C43,TED2021-131323B-I00,and PID2022-141712NB-C21)the María de Maeztu Program for Units of Excellence in R&D(grant no.CEX2018-000805-M)+2 种基金the Comunidad Autónoma de Madrid through the Recovery,Transformation and Resilience Plan from Spain,the NextGenerationEU plan from the European Union(MAD2D-CM-UAM7)the Generalitat Valenciana through Programa Prometeo(2021/017)The authors thankfully acknowledge RES resources provided by Universidad de Málaga in Picasso to FI-2024-2-0016.M.A.García-Blázquez acknowledges financial support from Universidad Autónoma de Madrid through an FPI-UAM grant.M.C.-G.is grateful to the Azrieli Foundation for the award of an Azrieli International Postdoctoral Fellowship.Additional computational resources were provided by the Weizmann Institute of Science at Chemfarm.M.C.-G.thanks Tonatiuh Rangel for providing the initial geometries of bulk and monolayer GeS.
文摘It is well-known that exciton effects are determinant to understanding the optical absorption spectrum of low-dimensional materials.However,the role of excitons in nonlinear optical responses has been much less investigated at the experimental level.Additionally,computational methods to calculate nonlinear conductivities in real materials are still not widespread,particularly taking into account excitonic interactions.We present a methodology to calculate the excitonic second-order optical responses in 2D materials relying on:(i)ab initio tight-binding Hamiltonians obtained by Wannier interpolation and(ii)solving the Bethe-Salpeter equation with effective electron-hole interactions.Here,in particular,we explore the role of excitons in the shift current of monolayer materials.Focusing on MoS_(2)and GeS monolayer systems,our results show that 2p-like excitons,which are dark in the linear response regime,yield a contribution to the photocurrent comparable to that of 1s-like excitons.Under radiation with intensity~104W/cm2,the excitonic theory predicts in-gap photogalvanic currents of almost~10 nA in sufficiently clean samples,which is typically one order of magnitude higher than the value predicted by independent-particle theory near the band edge.
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.
