Odd-parity superconductivity from phonons

Date

May 6, 2014

Time

2:50 PM - 3:50 PM

Speaker

Dr. Philip M. R. Brydon

Affiliation

Condensed Matter Theory Center, University of Maryland, USA

Language

en

Main Topic

Physik

Other Topics

Physik

Host

Dr. Marion Malkoc, DFG-Graduiertenkolleg "Itineranter Magnetismus und Supraleitung in intermetallischen Verbindungen"

Description

Doping a topological insulator has recently been proposed as a simple route to realizing a topological superconductor [1]. Much excitement has been generated by the apparent observation of topologically-protected edge states in superconducting Cu-doped Bi$_2$Se$_3$ [2], but the experimental situation remains controversial. Since these materials are weakly-correlated, the pairing is likely mediated by phonons. Although this usually favours a nontopological even-parity state, the presence of strong spin-orbit coupling has been suggested to favour topological odd-parity pairing. We resolve this controversy by proving that that for a purely phonon-mediated pairing interaction, the critical temperature of the leading odd-parity state cannot exceed that of the leading even-parity [3]. Electronic interactions are thus crucial for stabilizing a topological superconductor. Furthermore, for a given odd-parity state, we show how to identify the pair-forming and pair-breaking electron-phonon vertices according as they preserve or flip a "chirality" quantum number. To exemplify the power of our method, we study the
topological state in Cu-doped Bi$_2$Se$_3$, and identify the electron-phonon vertices which produce an attractive or repulsive interaction in the triplet channel. Implications for the physical pairing state our discussed.

[1] L. Fu and E. Berg, Phys. Rev. Lett. {\bf 105}, 097001 (2010).
[2] S. Sasaki, M. Kriener, K. Segawa, K. Yada, Y. Tanaka, M. Sato, and Y. Ando, Phys. Rev. Lett. {\bf 107}, 217001 (2011).
[3] P. M. R. Brydon, S. Das Sarma, H.-Y. Hui, and J. D. Sau, arXiv:1402.7061.

Links

• http://tu-dresden.de/veranstaltungen/termin?id=TUD53674c781b36c

Last modified: May 6, 2014, 9:36:44 AM