Two-dimensional systems with chiral symmetry allow stable discrete band crossings(nodal points) in Brillouin zones.Here we study the local evolutions of these nodal points under chiral symmetry preserving perturbation...Two-dimensional systems with chiral symmetry allow stable discrete band crossings(nodal points) in Brillouin zones.Here we study the local evolutions of these nodal points under chiral symmetry preserving perturbations.We find that these evolutions can be classified by different types of local k·p models around the nodal points.Several concrete examples are calculated to illustrate our results.展开更多
通过10带k·p模型计算,设计了能够激发3μm波长的In x Ga1-x As1-y Ny/AlAs量子阱结构的量子级联激光器有源区。In x Ga1-x As1-y Ny/AlAs异质结结构具有极宽的导带阶跃(～1.5 eV),并且能够通过成熟的GaAs基工艺生长,因此采用这种...通过10带k·p模型计算,设计了能够激发3μm波长的In x Ga1-x As1-y Ny/AlAs量子阱结构的量子级联激光器有源区。In x Ga1-x As1-y Ny/AlAs异质结结构具有极宽的导带阶跃(～1.5 eV),并且能够通过成熟的GaAs基工艺生长,因此采用这种结构制作短波量子级联激光器已成为研究热点。通过计算能带结构以及相应的波函数,发现当导带带阶非常大以致于第一激发态位于氮能级之上时,电子基态以及第一激发态会分裂为两条能级。正是由于这种效应的存在,提升了激光上能级的能量而促使激发波长缩短。通过一系列计算得出了一种最优化的基于In0.2Ga0.8As0.99N0.01/AlAs的三重耦合量子阱结构。在工作电压为65 kV/cm以及室温的条件下,最短的激光波长可以达到3μm。展开更多
The past decade has witnessed a surge of interest in exploring emergent particles in condensed matter systems.Novel particles,emerged as excitations around exotic band degeneracy points,continue to be reported in real...The past decade has witnessed a surge of interest in exploring emergent particles in condensed matter systems.Novel particles,emerged as excitations around exotic band degeneracy points,continue to be reported in real materials and artificially engineered systems,but so far,we do not have a complete picture on all possible types of particles that can be achieved.Here,via systematic symmetry analysis and modeling,we accomplish a complete list of all possible particles in time-reversal-invariant systems.This includes both spinful particles such as electron quasiparticles in solids,and spinless particles such as phonons or even excitations in electric-circuit and mechanical networks.We establish detailed correspondence between the particle,the symmetry condition,the effective model,and the topological character.This obtained encyclopedia concludes the search for novel emergent particles and provides concrete guidance to achieve them in physical systems.展开更多
The electronic properties of CdTe/ZnTe quantum rings （QRs） are investigated as functions of size and temperature using an eight-band strain-dependent k.p Hamiltonian. The size effects of diameter and height on the s...The electronic properties of CdTe/ZnTe quantum rings （QRs） are investigated as functions of size and temperature using an eight-band strain-dependent k.p Hamiltonian. The size effects of diameter and height on the strain distributions around the QRs are studied. We find that the interband transition energy, defined as the energy difference between the ground electronic and the ground heavy-hole subbands, increases with the increasing QR inner diameter regardless of the temperature, while the interband energy decreases with the increasing QR height, This is attributed to the reduction of subband energies in both the conduction and the valence bands due to the strain effects. Our model, in the framework of the finite element method and the theory of elasticity of solids, shows a good agreement with the temperature-dependent photoluminescence measurement of the interband transition energies.展开更多
基金Project supported by the National Basic Research Program of China(Grant Nos.2015CB921300 and 2017YFA0303100)the National Natural Science Foundation of China(Grant Nos.1190020,11534014,and 11334012)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB07000000 and XDB28000000)
文摘Two-dimensional systems with chiral symmetry allow stable discrete band crossings(nodal points) in Brillouin zones.Here we study the local evolutions of these nodal points under chiral symmetry preserving perturbations.We find that these evolutions can be classified by different types of local k·p models around the nodal points.Several concrete examples are calculated to illustrate our results.
基金supported by the National Key R&D Program of China(2020YFA0308800,2016YFA0300600,and 2017YFB0701600)the National Natural Science Foundation of China(11734003,12061131002,12004028,and 12004035)+3 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(XDB30000000)the China Postdoctoral Science Foundation(2020M670106)the Singapore Ministry of Education AcRF Tier 2(MOE2019-T2-1-001)Beijing Institute of Technology Research Fund Program for Young Schola。
文摘The past decade has witnessed a surge of interest in exploring emergent particles in condensed matter systems.Novel particles,emerged as excitations around exotic band degeneracy points,continue to be reported in real materials and artificially engineered systems,but so far,we do not have a complete picture on all possible types of particles that can be achieved.Here,via systematic symmetry analysis and modeling,we accomplish a complete list of all possible particles in time-reversal-invariant systems.This includes both spinful particles such as electron quasiparticles in solids,and spinless particles such as phonons or even excitations in electric-circuit and mechanical networks.We establish detailed correspondence between the particle,the symmetry condition,the effective model,and the topological character.This obtained encyclopedia concludes the search for novel emergent particles and provides concrete guidance to achieve them in physical systems.
基金Project supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF)the Ministry of Education,Science,and Technology,Korea (Grant No.2010-0024703)
文摘The electronic properties of CdTe/ZnTe quantum rings （QRs） are investigated as functions of size and temperature using an eight-band strain-dependent k.p Hamiltonian. The size effects of diameter and height on the strain distributions around the QRs are studied. We find that the interband transition energy, defined as the energy difference between the ground electronic and the ground heavy-hole subbands, increases with the increasing QR inner diameter regardless of the temperature, while the interband energy decreases with the increasing QR height, This is attributed to the reduction of subband energies in both the conduction and the valence bands due to the strain effects. Our model, in the framework of the finite element method and the theory of elasticity of solids, shows a good agreement with the temperature-dependent photoluminescence measurement of the interband transition energies.
