CePt3Si: an unconventional superconductor without inversion center

TL;DR

This paper investigates the unconventional superconductivity in CePt3Si, a heavy-fermion material lacking inversion symmetry, revealing unique pairing properties, gap structures, and electronic characteristics due to strong spin-orbit coupling.

Contribution

It provides a theoretical analysis of how the absence of inversion symmetry affects pairing symmetry and gap structure, supported by ab initio calculations showing strong spin-orbit effects.

Findings

Order parameter is an odd function of momentum.

Presence of lines of zeros in the excitation energy gap.

Strong spin-orbit coupling lifts band degeneracy except along high symmetry lines.

Abstract

Most superconducting materials have an inversion center in their crystal lattices. One of few exceptions is the recently discovered heavy-fermion superconductor CePt3Si [E. Bauer et al, Phys. Rev. Lett. 92, 027003 (2004)]. In this paper, we analyze the implications of the lack of inversion symmetry for the superconducting pairing. We show that the order parameter is an odd function of momentum, and that there always are lines of zeros in the excitation energy gap for one-component order parameters, which seems to agree with the experimental data. The superconducting phase can be non-uniform, even without external magnetic field, due to the presence of unusual gradient terms in the Ginzburg-Landau free energy. Also, we performed ab initio electronic structure calculations for CePt3Si, which showed that the spin-orbit coupling in this material is strong, and the degeneracy of the bands is lifted everywhere except along some high symmetry lines in the Brillouin zone.