Relation of Superconducting Pairing Symmetry and Non-Magnetic Impurity Effects in Vortex States

Yasuaki Sera,Hiroto Adachi,Masanori Ichioka,Takahiro Ueda

doi:10.3390/sym12010175

Yasuaki Sera, Hiroto Adachi + Show 2 more

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https://doi.org/10.3390/sym12010175

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Journal: Symmetry	Publication Date: Jan 18, 2020
Citations: 3	License type: CC BY 4.0

Affiliation: Okayama University, Okayama University of Science

Abstract

Non-magnetic impurity scattering effects on the vortex core states are theoretically studied to clarify the contributions from the sign-change of the pairing function in anisotropic superconductors. The vortex states are calculated by the Eilenberger theory in superconductors with p x -wave pairing symmetry, as well as the corresponding anisotropic s-wave symmetry. From the spatial structure of the pair potential and the local electronic states around a vortex, we examine the differences between anisotropic superconductors with and without sign-change of the pairing function, and estimate how twofold symmetric vortex core images change with increasing the impurity scattering rate both in the Born and the unitary limits. We found that twofold symmetric vortex core image of zero-energy local density of states changes the orientation of the twofold symmetry with increasing the scattering rate when the sign change occurs in the pairing function. Without the sign change, the vortex core shape reduces to circular one with approaching dirty cases. These results of the impurity effects are valuable for identifying the pairing symmetry by observation of the vortex core image by the STM observation.

Highlights

Superconductivity is caused by the long-range order of the pair potential, which is wave function of Cooper pair
To clarify contributions from the sign-change of the pairing function φ(θ ) in the non-magnetic impurity scattering effects on the vortex state, we studied the twofold symmetric vortex core structure of the pair potential |∆(r)| and the local density of states (LDOS) N ( E, r) in anisotropic superconductors with p x -wave pairing symmetry φ px (θ ) and anisotropic s-wave pairing φ| px | (θ )
The LDOS is accessible by the scanning tunneling microscope (STM) observation

Summary

Introduction

Superconductivity is caused by the long-range order of the pair potential, which is wave function of Cooper pair. At the vortex core where the pair potential is suppressed, low-energy bound states called. The local electronic structure of the bound state at the vortex core was experimentally observed by the scanning tunneling microscope (STM) observation by Hess et al [7,8,9]. The STM observations of the vortex core image have been performed to study exotic properties of superconductivity in many superconductors [10,11,12,13], including high-Tc cuprate superconductors [14,15,16,17,18,19], iron-based superconductors [20,21,22,23,24], and topological superconductors [24,25]

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