Tai Kai Ng

Majorana Fermion Induced Resonant Andreev Reflection

We describe experimental signatures of Majorana fermion edge states, which form at the interface between a superconductor and the surface of a topological insulator. If a lead couples to the Majorana fermions through electron tunneling, the Majorana fermions induce resonant Andreev reflections from the lead to the grounded superconductor. The linear tunneling conductance is 0 (2e(2)/h) if there is an even (odd) number of vortices in the superconductor. Similar resonance occurs for tunneling into the zero mode in the vortex core. We also study the current and noise of a two-lead device.

SU(2) FORMULATION OF THE T-J MODEL : APPLICATION TO UNDERDOPED CUPRATES

We develop a slave-boson theory for the

Broken Time-reversal Symmetry in Josephson Junction Involving Two-band Superconductors

t\ensuremath{-}J

Realization of 2D Spin-Orbit Interaction and Exotic Topological Orders in Cold Atoms

model at finite doping that respects an SU(2) symmetry: a symmetry previously known to be important at half filling. The mean-field phase diagram is found to be consistent with the phases observed in the cuprate superconductors, which contain

Spontaneous Vortex Phase Discovered

d

Selective equal-spin Andreev reflections induced by Majorana fermions.

-wave superconductor, spin-gap, strange metal, and Fermi-liquid phases. The spin-gap phase is best understood as the staggered flux phase, which is nevertheless translationally invariant for physical quantities. The physical electron spectral function shows small Fermi segments at low doping that continuously evolve into the large Fermi surface at high-doping concentrations. The close relation between the SU(2) and the U(1) slave-boson theory is discussed. The low-energy effective theory for the low-lying fluctuations is derived and additional lying modes [which were overlooked in the U(1) theory] are identified.

Detecting topological phases in cold atoms.

A novel time-reversal symmetry breaking state is found theoretically in the Josephson junction between a two-gap superconductor and a conventional s-wave superconductor. This occurs as a result of frustration between the three order parameters analogous to two antiferromagnetically coupled XY-spins put under a magnetic field. This leads to formation of interface states with energies inside the superconducting gap and modified flux quantization condition for a ring composed of the two types of superconductors.

Power-law conductivity inside the Mott gap: application to kappa-(BEDT-TTF)2Cu2(CN){3}.

Majorana zero bound mode exists in the vortex core of a chiral

Quantum Dot in a Two-Dimensional Topological Insulator: The Two-Channel Kondo Fixed Point

p+ip

EDGE STATES IN OPEN ANTIFERROMAGNETIC HEISENBERG CHAINS

superconductor or superfluid, which can be driven from an s-wave pairing state by two-dimensional (2D) spin-orbit (SO) coupling. We propose here a novel scheme based on realistic cold atom platforms to generate 2D SO interactions in a blue-detuned square optical lattice, and predict both the quantum anomalous Hall effect and chiral topological superfluid phase in the experimentally accessible parameter regimes. This work opens a new direction with experimental feasibility to observe non-Abelian topological orders in cold atom systems.