Stability of magnetic-field induced helical phase in Rashba superconductors

TL;DR

This paper develops a microscopic theory for Rashba superconductors, showing that the helical phase is generally stable over most of the phase diagram but can transition to a multiple-q phase with spatially varying order parameters.

Contribution

It provides a detailed analysis of the stability of the helical phase in Rashba superconductors and identifies conditions for phase transitions to multiple-q states.

Findings

Helical phase occupies most of the magnetic field-temperature phase diagram.

Transition point identified between helical and multiple-q phases.

Unique density of states features associated with the helical phase.

Abstract

Due to the lack of both parity and time reversal symmetries, the Rashba superconductors CePt_3Si, CeRhSi_3, and CeIrSi_3, in the presence of a magnetic field, are unstable to helical (single plane-wave) order. We develop a microscopic theory for such superconductors and examine the stability of this helical phase. We show that the helical phase typically occupies most of the magnetic field-temperature phase diagram. However, we also find that this phase is sometimes unstable to a multiple-q phase, in which both the magnitude and the phase of the order parameter are spatially varying. We find the position of this helical to multiple-q phase transition. We further examine the density of states and identify features unique to the helical phase.