Andreev spectroscopy and surface density of states for a three-dimensional time-reversal invariant topological superconductor

A topological superconductor is a fully gapped superconductor that exhibits exotic zero-energy Andreev surface states at interfaces with a normal metal. In this paper we investigate the properties of a three-dimensional time reversal invariant topological superconductor by means of a two-band model with unconventional pairing in both the inter- and intraband channels. Due to the bulk-boundary correspondence the presence of Andreev surface states in this system is directly related to the topological structure of the bulk wavefunctions, which is characterized by a winding number. Using quasiclassical scattering theory we construct the spectrum of the Andreev bound states that appear near the surface and compute the surface density of states for various surface orientations. Furthermore, we consider the effects of band splitting, i.e., the breaking of an inversion-type symmetry, and demonstrate that in the absence of band splitting there is a direct transition between the fully gapped topologically trivial phase and the nontrivial phase, whereas in the presence of band splitting there exists a finite region of a gapless nodal superconducting phase between the fully gapped topologically trivial and nontrivial phases.Comment: 7 pages, 4 figures, typos corrected, two footnotes adde

Varieties of liberalism: Anglo-Saxon capitalism in crisis?

‘Global financial crisis’ is an inaccurate description of the current upheaval in the world’s financial markets. The initial banking crisis did not affect all countries to the same degree. Notably, while the US and UK banking systems were badly hit, those of the other two major Anglo-Saxon economies, Canada and Australia, remain largely unscathed and have even gained in terms of global market share. The national business systems and comparative corporate governance literatures underscore the similarities among these four ‘liberal market economies’ (LMEs) and would predict similar trajectories. This paper investigates the reasons behind the differing performance of the Anglo-Saxon banking systems, which defy a verdict of failure of the LME variety of capitalism as such

Influence of higher d-wave gap harmonics on the dynamical magnetic susceptibility of high-temperature superconductors

Using a fermiology approach to the computation of the magnetic susceptibility measured by neutron scattering in hole-doped high-Tc superconductors, we estimate the effects on the incommensurate peaks caused by higher d-wave harmonics of the superconducting order parameter induced by underdoping. The input parameters for the Fermi surface and d-wave gap are taken directly from angle resolved photoemission (ARPES) experiments on Bi{2}Sr{2}CaCu{2}O{8+x} (Bi2212). We find that higher d-wave harmonics lower the momentum dependent spin gap at the incommensurate peaks as measured by the lowest spectral edge of the imaginary part in the frequency dependence of the magnetic susceptibility of Bi2212. This effect is robust whenever the fermiology approach captures the physics of high-Tc superconductors. At energies above the resonance we observe diagonal incommensurate peaks. We show that the crossover from parallel incommensuration below the resonance energy to diagonal incommensuration above it is connected to the values and the degeneracies of the minima of the 2-particle energy continuum.Comment: 13 pages, 7 figure

Fermion zero modes at the boundary of superfluid 3He-B

Superfluid 3He-B belongs to the important special class of time-reversal invariant topological superfluids. It has Majorana fermions as edge states on the surface of bulk 3He-B. On the rough wall these fermion zero modes have finite density of states at E=0. It is possible that Lancaster experiments with a wire vibrating in 3He-B have already probed Majorana fermions living on the surface of the wire.Comment: 4 pages, no Figures, JETP Letters style, version to be published in JETP Letter

Origin of Rashba-splitting in the quantized subbands at Bi2Se3 surface

We study the band structure of the $\text{Bi}_2\text{Se}_3$ topological insulator (111) surface using angle-resolved photoemission spectroscopy. We examine the situation where two sets of quantized subbands exhibiting different Rashba spin-splitting are created via bending of the conduction (CB) and the valence (VB) bands at the surface. While the CB subbands are strongly Rashba spin-split, the VB subbands do not exhibit clear spin-splitting. We find that CB and VB experience similar band bending magnitudes, which means, a spin-splitting discrepancy due to different surface potential gradients can be excluded. On the other hand, by comparing the experimental band structure to first principles LMTO band structure calculations, we find that the strongly spin-orbit coupled Bi 6$p$ orbitals dominate the orbital character of CB, whereas their admixture to VB is rather small. The spin-splitting discrepancy is, therefore, traced back to the difference in spin-orbit coupling between CB and VB in the respective subbands' regions