Persistent oscillation of a Cooper-pair condensate of topological defects in a nonintegrable quantum Ising chain

TL;DR

This paper discovers persistent oscillations of a Cooper-pair condensate of topological defects in a nonintegrable quantum Ising chain, revealing quantum coherence phenomena beyond integrable models.

Contribution

It demonstrates that adding next-nearest neighbor interactions induces persistent oscillations of a Cooper-pair condensate in a nonintegrable quantum Ising chain, a novel quantum coherence effect.

Findings

Persistent oscillations observed in nonintegrable zigzag Ising chain

Cooper pairs form among topological defects (kinks)

Oscillation frequency depends on binding energy gap

Abstract

We identify persistent oscillations in a nonintegrable quantum Ising chain. In the integrable chain with nearest-neighbor interactions, the nature, origin, and decay of post-transition oscillations are tied to the Kibble-Zurek mechanism. Remarkably, when coupling to the next-nearest neighbor is added, the resulting nonintegrable ''zigzag'' chain (still in the quantum Ising universality class) supports persistent oscillation: Topological defects (kinks) appear as a result of the quantum phase transition. However, in a ''zigzag'' Ising chain defects can form Cooper pairs. The oscillation of the Cooper-pair condensate has a frequency that depends on the binding energy gap between the paired and the unpaired defects, so it can be excited by resonant driving. While one might have expected that the integrability-breaking ''zigzag'' coupling causes relaxation, the oscillations we identify are persistent: Their longevity in our simulations is likely limited only by numerical accuracy. This oscillation of the Cooper-pair condensate of kinks is a manifestation of quantum coherence and should be experimentally accessible.