12,849 research outputs found
Thermopower and the Mott formula for a Majorana edge state
We study the thermoelectric effect between a conducting lead and a Majorana
edge state. In the tunneling limit, we first use the Landuaer-Buttiker
formalism to derive the Mott formula relating the thermopower and the
differential conductance between a conducting lead and a superconductor. When
the tunneling takes place between a conducting lead and a Majorana edge state,
we show that a non-vanishing thermopower can exist. Combining measurements of
the differential conductance and the voltage difference induced by the
temperature difference between the conducting lead and the edge state, the Mott
formula provides a unique way to infer the temperature of the Majorana edge
state.Comment: 9 pages, 3 figure
Topological Quantum Infidelity
Can topological quantum entanglement between anyons in one topological medium
"stray" into a different, topologically distinct medium? In other words, can
quantum information encoded non-locally in the combined state of non-Abelian
anyons be shared between two distinct topological media? We consider a setup
with two p-wave superconductors of opposite chirality and demonstrate that such
scenario is indeed possible. The information encoded in the fermionic parity of
two Majorana zero modes, originally within the same superconducting domain, can
be shared between the domains or moved entirely from one domain to another
provided that vortices can tunnel between them in a controlled fashion.Comment: 10 pages, 2 figure
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
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