Dynamic generation of nonequilibrium superconducting states in Kitaev chain

TL;DR

This paper explores how non-equilibrium dynamics in a Kitaev chain can lead to the formation of superconducting states, revealing that different pairing channels behave distinctly but both can identify phase diagrams.

Contribution

It introduces a method to analyze non-equilibrium superconducting states via two order parameters, revealing their behavior during quench dynamics and topological phase transitions.

Findings

In equilibrium, the two order parameters are identical, indicating a balance between pairing channels.

Out of equilibrium, the two order parameters differ but still reveal phase boundaries.

Non-equilibrium states favor BCS-like pairing in topologically non-trivial regions.

Abstract

Non-equilibrium state can exhibit the same macroscopic properties, such as conductivity or superconductivity, as a static state when they share the identical average of an observable over a period of time. We investigate the quench dynamics of a Kitaev chain by introducing two kinds of order parameters which relate to two channels of pairing, local pair in real space and BCS-like pair in momentum space. Based on exact solutions, we find that two order parameters are identical for the ground state, indicating the balance between two kinds of pairing channels, and can identify the quantum phase diagram. However, for a non-equilibrium state obtained by the time evolution from initially prepared vacuum state, the two are different but both can still clearly identify the phase diagram. In the topologically non-trivial region, the non-equilibrium states prefer the BCS-like pairing state. Our finding provides an alternative way to dynamically generate a superconducting state from a trivial empty state and sheds light on the mechanism of pairing.