725 research outputs found
Phase-locked magnetoconductance oscillations as a probe of Majorana edge states
We calculate the Andreev conductance of a superconducting ring interrupted by
a flux-biased Josephson junction, searching for electrical signatures of
circulating edge states. Two-dimensional pair potentials of spin-singlet d-wave
and spin-triplet p-wave symmetry support, respectively, (chiral) Dirac modes
and (chiral or helical) Majorana modes. These produce h/e-periodic
magnetoconductance oscillations of amplitude \simeq (e^{2}/h)N^{-1/2}, measured
via an N-mode point contact at the inner or outer perimeter of the grounded
ring. For Dirac modes the oscillations in the two contacts are independent,
while for an unpaired Majorana mode they are phase locked by a topological
phase transition at the Josephson junction.Comment: 10 pages, 6 figures. New appendix on the gauge invariant
discretization of the Bogoliubov-De Gennes equation. Accepted for publication
in PR
The "Coulomb phase" in frustrated systems
The "Coulomb phase" is an emergent state for lattice models (particularly
highly frustrated antiferromagnets) which have local constraints that can be
mapped to a divergence-free "flux". The coarse-grained version of this flux or
polarization behave analogously to electric or magnetic fields; in particular,
defects at which the local constraint is violated behave as effective charges
with Coulomb interactions. I survey the derivation of the characteristic
power-law correlation functions and the pinch-points in reciprocal space plots
of diffuse scattering, as well as applications to magnetic relaxation,
quantum-mechanical generalizations, phase transitions to long-range-ordered
states, and the effects of disorder.Comment: 30 pp, 5 figures (Sub. to Annual Reviews of Condensed Matter Physics
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