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Single- and Few-Electron States in Deformed Topological Insulator Quantum Dots

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Chinese Physics Letters 2015年第4期32卷 101-104页

作者：李健张东 sklsm Institute of SemiconductorsChinese Academy of Sciences

We theoretically investigate the single- and few-electron states in deformed HgTe quantum dots （QDs） with an inverted band structure using the full configuration interaction method. For the circular and deformed QD, it is found that the energy of edge states is robust against the shape from the circular QD in various elliptic ones. For the few electron states, electrons will firstly fill the edge states localized at the short axis, then the states localized at the long axis of the QD before filling the bulk states. The filling of the edge states can be controlled by tuning the dot size or the deformation of the geometry of the HgTe QD, respectively.

关键词： QDs Single and Few-Electron States in Deformed Topological Insulator Quantum Dots

Quantum pump effect in a four-terminal mesoscopic structure

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Journal of Semiconductors 2015年第2期36卷 6-9页

作者：王凯凯 sklsm Institute of Semiconductors Chinese Academy of Sciences

Quantum pump effect in a four-terminal mesoscopic structure constructed from a homogeneous two- dimensional electron gas is investigated. Oscillating electric potentials are applied to the two opposite terminals of the four-terminal mesoscopic structure. In both the remaining two opposite terminals and in the central region there are constant potentials that do not change with time. The oscillating potentials change slowly in comparison with all of the internal time scales of the structure and the amplitude of the oscillating potentials is small in comparison with the Fermi energy. The current of each lead and the transmission coefficients from one lead to another are calculated by using the non-equilibrium Green＇s function approach under the adiabatic approximation. In the remaining two opposite terminals of the four-terminal structure, the quantum pump effect can produce an electric current whose magnitude and direction depends on the Fermi energy. The pumped currents are ascribed to the asymmetry of transmission coefficients with respect to the Fermi energy.

关键词： quantum pump effect mesoscopic structure

Molybdenum Carbide:A Stable Topological Semimetal with Line Nodes and Triply Degenerate Points

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Chinese Physics Letters 2017年第2期34卷 83-87页

作者： Jian-Peng Sun Dong Zhang Kai Chang sklsm Institute of SemiconductorsChinese Academy of SciencesBeijing 100083

We propose that the hexagonal crystal form of MoC is a stable and new type of topological semimetal. It hosts an exotic Fermi surface consisting of two concentric nodal rings in the presence of spin-orbit coupling, and possesses four pairs of triply degenerate points （TDPs） in the vicinity of the Fermi energy. The coexistence of the nodal ring Fermi surface and TDPs in MoC leads to extraordinary properties such as distinguishable drumhead surface states and manipulatable new fermions, which make MoC a fertile platform for in-depth understanding of topological phenomena and a potential candidate material for topological electronic devices.

关键词： Topology

Topological Nodal Line Semimetal in Non-Centrosymmetric PbTaS2

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Chinese Physics Letters 2017年第7期34卷 199-202页

作者：孙建鹏 sklsm Institute of SemiconductorsChinese Academy of SciencesBeijing 100083

Topological semimetals are a new type of matter with one-dimensional Fermi lines or zero-dimensional Weyl or Dirac points in momentum space. Here using first-principles calculations, we find that the non-centrosymmetric PbTaS2 is a topological nodal line semimetal. In the absence of spin-orbit coupling （SOC）, one band inversion happens around a high symmetrical H point, which leads to forming a nodal line. The nodal line is robust and protected against gap opening by mirror reflection symmetry even with the inclusion of strong SOC. In addition, it also hosts exotic drumhead surface states either inside or outside the projected nodal ring depending on surface termination. The robust bulk nodal lines and drumhead-like surface states with SOC in PbTaS2 make it a potential candidate material for exploring the freakish properties of the topological nodal line fermions in condensed matter systems.

关键词： SOC Topological Nodal Line Semimetal in Non-Centrosymmetric PbTaS2 Pb

Spin Relaxation of Electrons in Single InAs Quantum Dots

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Chinese Physics Letters 2009年第11期26卷 177-179页

作者：马珊珊窦秀明常秀英孙宝权熊永华牛智川倪海桥 sklsm Institute of Semiconductors Chinese Academy of Sciences PO Box 912 Beijing 100083

By using polarization-resolved photoluminescence spectra, we study the electron spin relaxation in single InAs quantum dots （QDs） with the configuration of positively charged excitons X＋（one electron, two holes）. The spin relaxation rate of the hot electrons increases with the increasing energy of exciting photons. For electrons localized in QDs the spin relaxation is induced by hyperfine interaction with the nuclei. A rapid decrease of polarization degree with increasing temperature suggests that the spin relaxation mechanisms are mainly changed from the hyperfine interaction with nuclei into an electron-hole exchange interaction.

关键词： Condensed matter: electrical magnetic and optical Semiconductors Surfaces interfaces and thin films Nanoscale science and low-D systems

Tuning Photoluminescence Energy and Fine Structure Splitting in Single Quantum Dots by Uniaxial Stress

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Chinese Physics Letters 2008年第3期25卷 1120-1123页

作者：窦秀明孙宝权王宝瑞马珊珊周蓉黄社松倪海桥牛智川 sklsm Institute of Semiconductors Chinese Academy of Sciences PO Box 912 Beijing 100083

We report a photoluminescence （PL） energy red-shift of single quantum dots （QDs） by applying an in-plane compressive uniaxial stress along the [110] direction at a liquid nitrogen temperature. Uniaxial stress has an effect not only on the confinement potential in the growth direction which results in the PL shift, but also on the cylindrical symmetry of QDs which can be reflected by the change of the full width at half maximum of PL peak. This implies that uniaxial stress has an important role in tuning PL energy and fine structure splitting of QDs.

关键词： supernova explosion proto-neutron star shock wave

Topological insulating phase in commonly used semiconductors

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National Science Review 2014年第1期1卷 34-35页

作者： Kai Chang sklsm Institute of Semiconductors Chinese Academy of Sciences

Interface polarization between commonly used semiconductors provides a possible method to drive commonly used semiconductors into their topological insulating *** insulators(TIs)have attracted interest over recent years,with properties such as an insulating bulk region,robust metallic edges or surface modes and topological *** have potential applications ranging from spintronic devices to quantum computation[1–8].Despite recent progress,

关键词： Ga As Topological insulating phase in commonly used semiconductors

Single-Photon Emission from a Single InAs Quantum Dot

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Chinese Physics Letters 2008年第2期25卷 501-504页

作者：窦秀明孙宝权黄杜松倪海桥牛智川 sklsm Institute of Semiconductors Chinese Academy of Sciences PO Box 912 Beijing 100083

Excitation power-dependent micro-photoluminescence spectra and photon-correlation measurement are used to study the optical properties and photon statistics of single InAs quantum dots. Exciton and biexciton emissions, whose photoluminescence intensities have linear and quadratic excitation power dependences, respectively, are identified. Under pulsed laser excitation, the zero time delay peak of second order correlation function corresponding to exciton emission is well suppressed, which is a clear evidence of single photon emission.

关键词： pulsars x-ray spectra relativity and gravitation redshift

Single-Photon Emission at Liquid Nitrogen Temperature from a Single InAs/GaAs Quantum Dot

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Chinese Physics Letters 2008年第9期25卷 3231-3233页

作者：窦秀明孙宝权常秀英熊永华黄社松倪海桥牛智川 sklsm Institute of Semiconductors Chinese Academy of Sciences PO Box 912 Beijing 100083

We report on the single photon emission from single InAs/GaAs self-assembled Stranski-Krastanow quantum dots up to 80 K under pulsed and continuous wave excitations. At temperature 8OK, the second-order correlation function at zero time delay, g^（2）（0）, is measured to be 0.422 for pulsed excitation. At the same temperature under continuous wave excitation, the photon antibunching effect is observed. Thus, our experimental results demonstrate a promising potential application of self-assembled InAs/GaAs quantum dots in single photon emission at liquid nitrogen temperature.

关键词： the power-law exponents precipitation durative abrupt precipitation change