Dirac surface states and nature of superconductivity in Noncentrosymmetric BiPd

In non-magnetic bulk materials, inversion symmetry protects the spin degeneracy. If the bulk crystal structure lacks a centre of inversion, however, spin–orbit interactions lift the spin degeneracy, leading to a Rashba metal whose Fermi surfaces exhibit an intricate spin texture. In superconducting...

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Main Authors:	Sun, Zhixiang, Enayat, Mostafa, Maldonado, Ana, Lithgow, Calum, Yelland, Ed, Peets, Darren C., Yaresko, Alexander, Schnyder, Andreas P., Wahl, Peter
Format:	Online
Language:	English
Published:	Nature Pub. Group 2015
Online Access:	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4389226/

id	pubmed-4389226
recordtype	oai_dc
spelling	pubmed-43892262015-04-17 Dirac surface states and nature of superconductivity in Noncentrosymmetric BiPd Sun, Zhixiang Enayat, Mostafa Maldonado, Ana Lithgow, Calum Yelland, Ed Peets, Darren C. Yaresko, Alexander Schnyder, Andreas P. Wahl, Peter Article In non-magnetic bulk materials, inversion symmetry protects the spin degeneracy. If the bulk crystal structure lacks a centre of inversion, however, spin–orbit interactions lift the spin degeneracy, leading to a Rashba metal whose Fermi surfaces exhibit an intricate spin texture. In superconducting Rashba metals a pairing wavefunction constructed from these complex spin structures will generally contain both singlet and triplet character. Here we examine the possible triplet components of the order parameter in noncentrosymmetric BiPd, combining for the first time in a noncentrosymmetric superconductor macroscopic characterization, atomic-scale ultra-low-temperature scanning tunnelling spectroscopy, and relativistic first-principles calculations. While the superconducting state of BiPd appears topologically trivial, consistent with Bardeen–Cooper–Schrieffer theory with an order parameter governed by a single isotropic s-wave gap, we show that the material exhibits Dirac-cone surface states with a helical spin polarization. Nature Pub. Group 2015-03-30 /pmc/articles/PMC4389226/ /pubmed/25818338 http://dx.doi.org/10.1038/ncomms7633 Text en Copyright © 2015, Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved. http://creativecommons.org/licenses/by/4.0/ This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
repository_type	Open Access Journal
institution_category	Foreign Institution
institution	US National Center for Biotechnology Information
building	NCBI PubMed
collection	Online Access
language	English
format	Online
author	Sun, Zhixiang Enayat, Mostafa Maldonado, Ana Lithgow, Calum Yelland, Ed Peets, Darren C. Yaresko, Alexander Schnyder, Andreas P. Wahl, Peter
spellingShingle	Sun, Zhixiang Enayat, Mostafa Maldonado, Ana Lithgow, Calum Yelland, Ed Peets, Darren C. Yaresko, Alexander Schnyder, Andreas P. Wahl, Peter Dirac surface states and nature of superconductivity in Noncentrosymmetric BiPd
author_facet	Sun, Zhixiang Enayat, Mostafa Maldonado, Ana Lithgow, Calum Yelland, Ed Peets, Darren C. Yaresko, Alexander Schnyder, Andreas P. Wahl, Peter
author_sort	Sun, Zhixiang
title	Dirac surface states and nature of superconductivity in Noncentrosymmetric BiPd
title_short	Dirac surface states and nature of superconductivity in Noncentrosymmetric BiPd
title_full	Dirac surface states and nature of superconductivity in Noncentrosymmetric BiPd
title_fullStr	Dirac surface states and nature of superconductivity in Noncentrosymmetric BiPd
title_full_unstemmed	Dirac surface states and nature of superconductivity in Noncentrosymmetric BiPd
title_sort	dirac surface states and nature of superconductivity in noncentrosymmetric bipd
description	In non-magnetic bulk materials, inversion symmetry protects the spin degeneracy. If the bulk crystal structure lacks a centre of inversion, however, spin–orbit interactions lift the spin degeneracy, leading to a Rashba metal whose Fermi surfaces exhibit an intricate spin texture. In superconducting Rashba metals a pairing wavefunction constructed from these complex spin structures will generally contain both singlet and triplet character. Here we examine the possible triplet components of the order parameter in noncentrosymmetric BiPd, combining for the first time in a noncentrosymmetric superconductor macroscopic characterization, atomic-scale ultra-low-temperature scanning tunnelling spectroscopy, and relativistic first-principles calculations. While the superconducting state of BiPd appears topologically trivial, consistent with Bardeen–Cooper–Schrieffer theory with an order parameter governed by a single isotropic s-wave gap, we show that the material exhibits Dirac-cone surface states with a helical spin polarization.
publisher	Nature Pub. Group
publishDate	2015
url	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4389226/
_version_	1613208857999310848

Dirac surface states and nature of superconductivity in Noncentrosymmetric BiPd

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