Manipulation of the induced pair potential in topological insulator-superconductor hybrid junctions

DIPC Seminars

Dr. Pablo Burset. University of Würzburg
Seminar room at the first floor of DIPC 1.
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Manipulation of the induced pair potential in topological insulator-superconductor hybrid junctions The interplay between the spin-orbit coupling at the surface of a topological insulator (TI), the conventional pair potential from a superconductor, and an external magnetic field creates a very exotic induced pair potential in a TI- based normal-superconductor junction. In addition to a superposition of spin- singlet and triplet components, a new, unconventional type of superconducting condensate can be induced in this system: one with a spin-triplet component that is both odd in frequency and even in its spatial coordinates. An unambiguous experimental detection of such odd-frequency condensate has not been achieved. We propose a detection scheme based on nonlocal conductance measurements on the one-dimensional edge of a two-dimensional TI: we show a one-to-one correspondence between crossed Andreev reflection processes and the emergence of odd-frequency triplet superconductivity [1]. We also consider the proximity effect on a three-dimensional TI-superconductor junction under the effect of an external magnetic field [2]. We find that the magnetic field induces even- and odd-frequency spin-triplet terms in the pairing amplitude, which are always superposed with an even-frequency spin- singlet term. The competition between all these components results in a rich subgap structure with emerging zero-energy peaks. Using very basic ingredients such as a conventional superconductor and an external magnetic field, standard experimental techniques like conductance spectroscopy can be used to detect signatures of odd-frequency superconductivity. [1] F. Crépin, P. Burset, B. Trauzettel, arXiv:1503.07784. [2] P. Burset, B. Lu, G. Tkachov, Y. Tanaka, E.M. Hankiewicz, B. Trauzettel, in preparation.