Helical vortex phase in the non-centrosymmetric CePt_3Si

TL;DR

This paper investigates the influence of magnetic fields on the non-centrosymmetric superconductor CePt_3Si, revealing a helical vortex phase that affects critical fields and can be experimentally detected via Josephson junction interference patterns.

Contribution

It introduces the concept of a helical vortex phase in CePt_3Si and demonstrates its necessity for explaining experimental critical field measurements, proposing a method to detect this phase.

Findings

Weak paramagnetic effect for fields along the c-axis

Strong reduction of in-plane paramagnetic effect due to helical order

Predicted Josephson interference pattern as a signature of helical order

Abstract

We consider the role of magnetic fields on the broken inversion superconductor CePt_3Si. We show that upper critical field for a field along the c-axis exhibits a much weaker paramagnetic effect than for a field applied perpendicular to the c-axis. The in-plane paramagnetic effect is strongly reduced by the appearance of helical structure in the order parameter. We find that to get good agreement between theory and recent experimental measurements of H_{c2}, this helical structure is required. We propose a Josephson junction experiment that can be used to detect this helical order. In particular, we predict that Josephson current will exhibit a magnetic interference pattern for a magnetic field applied perpendicular to the junction normal. We also discuss unusual magnetic effects associated with the helical order.