4,837 research outputs found
Quantum percolation in quantum spin Hall antidot systems
We study the influences of antidot-induced bound states on transport
properties of two- dimensional quantum spin Hall insulators. The bound
statesare found able to induce quantum percolation in the originally insulating
bulk. At some critical antidot densities, the quantum spin Hall phase can be
completely destroyed due to the maximum quantum percolation. For systems with
periodic boundaries, the maximum quantum percolationbetween the bound states
creates intermediate extended states in the bulk which is originally gapped and
insulating. The antidot in- duced bound states plays the same role as the
magnetic field inthe quantum Hall effect, both makes electrons go into
cyclotron motions. We also draw an analogy between the quantum percolation
phenomena in this system and that in the network models of quantum Hall effect
Surface-edge state and half quantized Hall conductance in topological insulators
We propose a surface-edge state theory for half quantized Hall conductance of
surface states in topological insulators. The gap opening of a single Dirac
cone for the surface states in a weak magnetic field is demonstrated. We find a
new surface state resides on the surface edges and carries chiral edge current,
resulting in a half-quantized Hall conductance in a four-terminal setup. We
also give a physical interpretation of the half quantized conductance by
showing that this state is the product of splitting of a boundary bound state
of massive Dirac fermions which carries a conductance quantum
Electric field modulation of topological order in thin film semiconductors
We propose a method that can consecutively modulate the topological orders or
the number of helical edge states in ultrathin film semiconductors without a
magnetic field. By applying a staggered periodic potential, the system
undergoes a transition from a topological trivial insulating state into a
non-trivial one with helical edge states emerging in the band gap. Further
study demonstrates that the number of helical edge state can be modulated by
the amplitude and the geometry of the electric potential in a step-wise
fashion, which is analogous to tuning the integer quantum Hall conductance by a
megntic field. We address the feasibility of experimental measurement of this
topological transition.Comment: 4 pages, 4 figure
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