By using scanning tunneling microscope induced luminescence(STML)technique,we investigate systematically the bias-polarity dependent electroluminescence behavior of a single platinum phthalocyanine(PtPc)molecule and t...By using scanning tunneling microscope induced luminescence(STML)technique,we investigate systematically the bias-polarity dependent electroluminescence behavior of a single platinum phthalocyanine(PtPc)molecule and the electron excitation mechanisms behind.The molecule is found to emit light at both bias polarities but with different emission energies.At negative excitation bias,only the fluorescence at 637 nm is observed,which originates from the LUMOtHOMO transition of the neutral PtPc molecule and exhibits stepwise-like increase in emission intensities over three different excitation-voltage regions.Strong fluorescence in region(I)is excited by the carrier injection mechanism with holes injected into the HOMO state first;moderate fluorescence in region(II)is excited by the inelastic electron scattering mechanism;and weak fluorescence in region(III)is associated with an up-conversion process and excited by a combined carrier injection and inelastic electron scattering mechanism involving a spintriplet relay state.At positive excitation bias,more-than-one emission peaks are observed and the excitation and emission mechanisms become complicated.The sharp moleculespecific emission peak at〜911 nm is attributed to the anionic emission of PtPc-originated from the LUMO+1 tLUMO transition,whose excitation is dominated by a carrier injection mechanism with electrons first injected into the LUMO+1 or higher-lying empty orbitals.展开更多
We performed ultra-low temperature thermal conductivity measurements on the single crystal of a new gold-based quasi-two-dimensional superconductor Au Te2Se(4/3), which has a superconducting transition temperature T...We performed ultra-low temperature thermal conductivity measurements on the single crystal of a new gold-based quasi-two-dimensional superconductor Au Te2Se(4/3), which has a superconducting transition temperature Tc = 2.70 K. A negligible residual linear term κ0/T in zero magnetic field is observed, which suggests fully gapped superconducting state.Furthermore, the field dependence of κ0/T is similar to that of the multi-band s-wave superconductor Ba Fe1.9 Ni0.1 As2 at low field. These results reveal multiple nodeless superconducting gaps in this interesting quasi-two-dimensional superconductor with Berezinsky–Kosterlitz–Thouless topological transition.展开更多
Single-molecule tip-enhanced Raman spectroscopy(TERS)has emerged as an important technique for structural analysis at sub-molecular scale.Here in this work,we report a TERS study of an isolated free-base porphyrin mol...Single-molecule tip-enhanced Raman spectroscopy(TERS)has emerged as an important technique for structural analysis at sub-molecular scale.Here in this work,we report a TERS study of an isolated free-base porphyrin molecule adsorbed on the Ag(100)surface at cryogenic temperature(~7 K).Site-dependent TERS spectra reveal distinct local vibrational information for the chemical constituents within a single molecule.Moreover,distinct spatial features among different Raman peaks can be resolved from the TERS mapping images.These images are found to associate with related vibrational modes,enabling to resolve the mode associated with N-H bonds at the sub-nanometer level.This study will provide deep insights into the symmetry of adsorption configurations and local vibrational information within a single molecule.展开更多
基金This work is supported by the National Key R&D Program of China(No.2016YFA0200600 and No.2017YFA0303500)the National Natural Science Foundation of China,the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36000000)Anhui Initiative in Quantum Information Technologies.
文摘By using scanning tunneling microscope induced luminescence(STML)technique,we investigate systematically the bias-polarity dependent electroluminescence behavior of a single platinum phthalocyanine(PtPc)molecule and the electron excitation mechanisms behind.The molecule is found to emit light at both bias polarities but with different emission energies.At negative excitation bias,only the fluorescence at 637 nm is observed,which originates from the LUMOtHOMO transition of the neutral PtPc molecule and exhibits stepwise-like increase in emission intensities over three different excitation-voltage regions.Strong fluorescence in region(I)is excited by the carrier injection mechanism with holes injected into the HOMO state first;moderate fluorescence in region(II)is excited by the inelastic electron scattering mechanism;and weak fluorescence in region(III)is associated with an up-conversion process and excited by a combined carrier injection and inelastic electron scattering mechanism involving a spintriplet relay state.At positive excitation bias,more-than-one emission peaks are observed and the excitation and emission mechanisms become complicated.The sharp moleculespecific emission peak at〜911 nm is attributed to the anionic emission of PtPc-originated from the LUMO+1 tLUMO transition,whose excitation is dominated by a carrier injection mechanism with electrons first injected into the LUMO+1 or higher-lying empty orbitals.
基金supported by the Key Basic Research Program of China(Grant Nos.2015CB921401 and 2016YFA0300503)the National Natural Science Foundation of China(Grant Nos.11422429 and 11421404)+2 种基金China Postdoctoral Science Foundation(Grant No.2016T90332)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,and STCSM of China(Grant No.15XD1500200)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB04040200)
文摘We performed ultra-low temperature thermal conductivity measurements on the single crystal of a new gold-based quasi-two-dimensional superconductor Au Te2Se(4/3), which has a superconducting transition temperature Tc = 2.70 K. A negligible residual linear term κ0/T in zero magnetic field is observed, which suggests fully gapped superconducting state.Furthermore, the field dependence of κ0/T is similar to that of the multi-band s-wave superconductor Ba Fe1.9 Ni0.1 As2 at low field. These results reveal multiple nodeless superconducting gaps in this interesting quasi-two-dimensional superconductor with Berezinsky–Kosterlitz–Thouless topological transition.
基金supported by the National Key R&D Program of China(No.2016YFA0200600)the National Natural Science Foundation of China,the Chinese Academy of Sciences+1 种基金Anhui Initiative in Quantum Information TechnologiesAtif Ghafoor acknowledges support by the China Scholarship Council
文摘Single-molecule tip-enhanced Raman spectroscopy(TERS)has emerged as an important technique for structural analysis at sub-molecular scale.Here in this work,we report a TERS study of an isolated free-base porphyrin molecule adsorbed on the Ag(100)surface at cryogenic temperature(~7 K).Site-dependent TERS spectra reveal distinct local vibrational information for the chemical constituents within a single molecule.Moreover,distinct spatial features among different Raman peaks can be resolved from the TERS mapping images.These images are found to associate with related vibrational modes,enabling to resolve the mode associated with N-H bonds at the sub-nanometer level.This study will provide deep insights into the symmetry of adsorption configurations and local vibrational information within a single molecule.