Publications (3)0 Total impact
ABSTRACT: Exotic excitations arise at the interface between a three-dimensional
topological insulator (TI) and superconductors. For example, Majorana fermions
with a linear dispersion, $E\sim k$, exist in a short $\pi$ Josephson junction
on the TI surface. We show that in these systems, the Andreev bound states
spectrum becomes nearly flat at zero energy when the chemical potential is
sufficiently away from the Dirac point. The flat dispersion is well
approximated by $E\sim k^N$, where $N$ scales with the chemical potential.
Similar evolution from linear to flat dispersion also occurs for the subgap
spectrum of a periodic superconducting proximity structure, such as a TI
surface in contact with a stripe superconductor.
ABSTRACT: We present microscopic, self-consistent calculations of the superconducting
order parameter and pairing correlations near the interface of an $s$-wave
superconductor and a three-dimensional topological insulator with spin-orbit
coupling. We discuss the suppression of the order parameter by the topological
insulator and show that the equal-time pair correlation functions in the
triplet channel, induced by spin-flip scattering at the interface, are of
$p_x\pm i p_y$ symmetry. We verify that the spectrum at sub-gap energies is
well described by the Fu-Kane model. The sub-gap modes are viewed as interface
states with spectral weight penetrating well into the superconductor. We
extract the phenomenological parameters of the Fu-Kane model from microscopic
calculations, and find they are strongly renormalized from the bulk material
parameters. This is consistent with previous results of Stanescu et al for a
lattice model using perturbation theory in the tunneling limit.
ABSTRACT: We compute the spin-active scattering matrix and the local spectrum at the
interface between a metal and a three-dimensional topological band insulator.
We show that there exists a critical incident angle at which complete (100%)
spin flip reflection occurs and the spin rotation angle jumps by $\pi$. We
discuss the origin of this phenomena, and systematically study the dependence
of spin-flip and spin-conserving scattering amplitudes on the interface
transparency and metal Fermi surface parameters. The interface spectrum
contains a well-defined Dirac cone in the tunneling limit, and smoothly evolves
into a continuum of metal induced gap states for good contacts. We also
investigate the complex band structure of Bi$_2$Se$_3$.