12,635 research outputs found
Electron fractionalization in two-dimensional graphenelike structures
Electron fractionalization is intimately related to topology. In
one-dimensional systems, fractionally charged states exist at domain walls
between degenerate vacua. In two-dimensional systems, fractionalization exists
in quantum Hall fluids, where time-reversal symmetry is broken by a large
external magnetic field. Recently, there has been a tremendous effort in the
search for examples of fractionalization in two-dimensional systems with
time-reversal symmetry. In this letter, we show that fractionally charged
topological excitations exist on graphenelike structures, where quasiparticles
are described by two flavors of Dirac fermions and time-reversal symmetry is
respected. The topological zero-modes are mathematically similar to fractional
vortices in p-wave superconductors. They correspond to a twist in the phase in
the mass of the Dirac fermions, akin to cosmic strings in particle physics.Comment: 4 pages, 2 figure
Corner Junction as a Probe of Helical Edge States
We propose and analyze inter-edge tunneling in a quantum spin Hall corner
junction as a means to probe the helical nature of the edge states. We show
that electron-electron interactions in the one-dimensional helical edge states
result in Luttinger parameters for spin and charge that are intertwined, and
thus rather different than those for a quantum wire with spin rotation
invariance. Consequently, we find that the four-terminal conductance in a
corner junction has a distinctive form that could be used as evidence for the
helical nature of the edge states.Comment: 4+ pages, 3 figure
"Wormhole" geometry for entrapping topologically-protected qubits in non-Abelian quantum Hall states and probing them with voltage and noise measurements
We study a tunneling geometry defined by a single point-contact constriction
that brings to close vicinity two points sitting at the same edge of a quantum
Hall liquid, shortening the trip between the otherwise spatially separated
points along the normal chiral edge path. This ``wormhole''-like geometry
allows for entrapping bulk quasiparticles between the edge path and the tunnel
junction, possibly realizing a topologically protected qubit if the
quasiparticles have non-Abelian statistics. We show how either noise or simpler
voltage measurements along the edge can probe the non-Abelian nature of the
trapped quasiparticles.Comment: 5 pages, 2 figue
- …