Because of the helicity of electrons in HgTe quantum wells（QWs） with inverted band structures,the electrons cannot be confined by electric barriers since electrons can tunnel the barriers perfectly without backscatt...Because of the helicity of electrons in HgTe quantum wells（QWs） with inverted band structures,the electrons cannot be confined by electric barriers since electrons can tunnel the barriers perfectly without backscattering in the HgTe QWs.This behavior is similar to Dirac electrons in graphene.In this paper,we propose a scheme to confine carriers in HgTe QWs using an electric-magnetic barrier.We calculate the transmission of carriers in 2-dimensional HgTe QWs and find that the wave-vector filtering effect of local magnetic fields can confine the carriers.The confining effect will have a potential application in nanodevices based on HgTe QWs.展开更多
The quantum spin Hall effect （QSHE） was first realized in HgTe quantum wells （QWs）, which remain the only known two-dimensional topological insulator so far. In this paper, we have systematically studied the effec...The quantum spin Hall effect （QSHE） was first realized in HgTe quantum wells （QWs）, which remain the only known two-dimensional topological insulator so far. In this paper, we have systematically studied the effect of the thickness fluctuation of HgTe QWs on the QSHE. We start with the case of constant mass with random distributions, and reveal that the disordered system can be well described by a virtual uniform QW with an effective mass when the number of components is small. When the number is infinite and corresponds to the real fluctuation, we find that the QSHE is not only robust, but also can be generated by relatively strong fluctuation. Our results imply that the thickness fluctuation does not cause backscattering, and the QSHE is robust to it.展开更多
We investigate theoretically the carrier transport in a two-dimensional topological insulator of(001)HgTe/CdTe quantum-well heterostructure with inverted band,and find distinct switchable features of the transmission ...We investigate theoretically the carrier transport in a two-dimensional topological insulator of(001)HgTe/CdTe quantum-well heterostructure with inverted band,and find distinct switchable features of the transmission spectra in the topological edge states by designing the double-electric modulation potentials.The transmission spectra exhibit the significant Fabry–Pérot resonances for the double-electric transport system.Furthermore,the transmission properties show rich behaviors when the Fermi energy lies in the different locations in the energy spectrum and the double-electric barrier regions.The opacity and transparency of the double-modulated barrier regions can be controlled by tuning the modulated potentials,Fermi energy and the length of modulated regions.This electrical switching behavior can be realized by tuning the voltages applied on the metal gates.The Fabry–Pérot resonances leads to oscillations in the transmission which can be observed in experimentally.This electric modulated-mechanism provides us a realistic way to switch the transmission in edge states which can be constructed in low-power information processing devices.展开更多
Theelectronicstructureof（InSb）m/（HgTe）nshortperiodsuperlatticesgrownalongthe（001）directionis studiedtheoreticallyusingnorm-conservingpseudo-potentialstogetherwiththelocal-densityapproximationforthe exchange-corr...Theelectronicstructureof（InSb）m/（HgTe）nshortperiodsuperlatticesgrownalongthe（001）directionis studiedtheoreticallyusingnorm-conservingpseudo-potentialstogetherwiththelocal-densityapproximationforthe exchange-correlationpotential.Thebandstructuredependsonthevalueofmandn,thenumberofmono-layersand on the ordering of atoms at the InSb/HgTe interface in one unit cell. Our calculation indicates that the superlattice can be a semiconductor having a band gap between the occupied and unoccupied bands, or a metal with no band gap at the Fermi energy. According to the further calculation of total charge density between（InSb）m/（HgTe）nwith different structures, a clearly different behavior happens when the structure changes from a system with a gap and a system without a gap.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10821403 and 11047131)the National Basic Research Program of China(Grant No. 2009CB929100)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20101303120005)
文摘Because of the helicity of electrons in HgTe quantum wells（QWs） with inverted band structures,the electrons cannot be confined by electric barriers since electrons can tunnel the barriers perfectly without backscattering in the HgTe QWs.This behavior is similar to Dirac electrons in graphene.In this paper,we propose a scheme to confine carriers in HgTe QWs using an electric-magnetic barrier.We calculate the transmission of carriers in 2-dimensional HgTe QWs and find that the wave-vector filtering effect of local magnetic fields can confine the carriers.The confining effect will have a potential application in nanodevices based on HgTe QWs.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11104189 and 11074023)the National Basic Research Program of China (Grant Nos. 2011CBA00102,2011CB921700,and 2012CB821403)
文摘The quantum spin Hall effect （QSHE） was first realized in HgTe quantum wells （QWs）, which remain the only known two-dimensional topological insulator so far. In this paper, we have systematically studied the effect of the thickness fluctuation of HgTe QWs on the QSHE. We start with the case of constant mass with random distributions, and reveal that the disordered system can be well described by a virtual uniform QW with an effective mass when the number of components is small. When the number is infinite and corresponds to the real fluctuation, we find that the QSHE is not only robust, but also can be generated by relatively strong fluctuation. Our results imply that the thickness fluctuation does not cause backscattering, and the QSHE is robust to it.
基金Project supported by the College Innovation Project of Guangdong Province(Grant No.2020KTSCX329)the Social Public Welfare and Basic Research Project of Zhongshan City(Grant No.2020B2044)+2 种基金Zhongshan Polytechnic Highlevel Talents Project(Grant No.KYG2102)the National Key R&D Program of China(Grant No.2021YFA1200502)the National Natural Science Foundation of China(Grant No.12174423)。
文摘We investigate theoretically the carrier transport in a two-dimensional topological insulator of(001)HgTe/CdTe quantum-well heterostructure with inverted band,and find distinct switchable features of the transmission spectra in the topological edge states by designing the double-electric modulation potentials.The transmission spectra exhibit the significant Fabry–Pérot resonances for the double-electric transport system.Furthermore,the transmission properties show rich behaviors when the Fermi energy lies in the different locations in the energy spectrum and the double-electric barrier regions.The opacity and transparency of the double-modulated barrier regions can be controlled by tuning the modulated potentials,Fermi energy and the length of modulated regions.This electrical switching behavior can be realized by tuning the voltages applied on the metal gates.The Fabry–Pérot resonances leads to oscillations in the transmission which can be observed in experimentally.This electric modulated-mechanism provides us a realistic way to switch the transmission in edge states which can be constructed in low-power information processing devices.
文摘Theelectronicstructureof（InSb）m/（HgTe）nshortperiodsuperlatticesgrownalongthe（001）directionis studiedtheoreticallyusingnorm-conservingpseudo-potentialstogetherwiththelocal-densityapproximationforthe exchange-correlationpotential.Thebandstructuredependsonthevalueofmandn,thenumberofmono-layersand on the ordering of atoms at the InSb/HgTe interface in one unit cell. Our calculation indicates that the superlattice can be a semiconductor having a band gap between the occupied and unoccupied bands, or a metal with no band gap at the Fermi energy. According to the further calculation of total charge density between（InSb）m/（HgTe）nwith different structures, a clearly different behavior happens when the structure changes from a system with a gap and a system without a gap.
