Quantum Dynamics of Small-Size Triplet Superconductors with Broken Time-Reversal Symmetry

TL;DR

This paper predicts that small triplet superconductors with broken time-reversal symmetry can exhibit macroscopic quantum tunneling and coherent oscillations, leading to observable effects like oscillating voltages and boundary current sign changes.

Contribution

It introduces the concept of quantum tunneling lifting degeneracy in small triplet superconductors and predicts observable quantum oscillations in such systems.

Findings

Degeneracy can be lifted via macroscopic quantum tunneling.

Coherent oscillations of magnetic momentum are possible.

Oscillating voltage features are predicted in the spontaneous Hall effect.

Abstract

Symmetry of the order parameter in some triplet superconductors corresponds to doubly-degenerate chiral states. We predict that in a sufficiently small sample this degeneracy can be lifted via macroscopic quantum tunneling. Moreover, if the initial state is prepared correspondingly, 'instanton'-like quantum behavior is possible in a single-domain sample. In this case coherent oscillations of magnetic momentum should take place, as well as the sign alternations of the boundary currents. In particular, spontaneous Hall-effect recently predicted for ruthenates should posses the oscillating voltage feature.