2017/03/31 by Jie Lu, Mei Li, Bin Xi · 1 citation
Chemistry · Physics and Astronomy · #Advanced Physical and Chemical Molecular Interactions #Degenerate energy levels #Electron #Hamiltonian (control theory) #Phase diagram #Phase transition #Quantum and electron transport phenomena #Quantum phase transition #Quantum tunnelling #Scalar (mathematics) #Symplectic geometry #Topological Materials and Phenomena #Unitary state #cond-mat.mes-hall
paper · pdf · doi:10.1088/1367-2630/aad6d6
published in New Journal of Physics 20(8), 083017 (IOP Publishing) · 17 pages, 12 figures
arxiv created 2017/10/19 · openalex publication_date 2018/07/30 · arxiv updated 2018/08/13 · openalex created_date 2019/07/30 · openalex updated_date 2026/08/05
We consider Anderson transitions in two-dimensional (2D) spinful electron gases subject to random scalar potentials with time-reversal-symmetric spin-mixing tunneling (SMT) and spin-preserving tunneling (SPT) at potential saddle points (PSPs). A symplectic quantum network model (QNM), named as SMT-QNM, is constructed in which SMT and SPT have the same status and contribute independent tunneling channels rather than sharing a total-probability-fixed one. 2D continuous Dirac Hamiltonian is then extracted out from this discrete network model as the generator of certain unitary transformation. With the help of high-accuracy numerics based on transfer matrix technique, finite-size analysis on two-terminal conductance and normalized localization length provides a phase diagram drawn in the SMT–SPT plane. As a manifestation of symplectic ensembles, a normal-metal (NM) phase emerges between the quantum spin Hall (QSH) and normal-insulator (NI) phases when SMT appears. We systematically analyze the quantum phases on the boundary and in the interior of the phase space. Particularly, the phase diagram is closely related to that of disordered three-dimensional weak topological insulators by appropriate parameter mapping. At last, if time-reversal symmetry in electron trajectories between PSPs is destroyed, the system falls into unitary class with no more NM phase. A direct SMT-driven transition from QSH to NI phases exists and can be explained by spin-flip backscattering between the degenerate doublets at the same sample edge.