Observation of dynamical phase transitions in a topological nanomechanical system

TL;DR

This paper demonstrates the experimental observation of dynamical phase transitions in a topological nanomechanical system by measuring the Pancharatnam geometric phase, utilizing chiral symmetry to eliminate dynamical phase interference.

Contribution

It introduces a novel scheme to observe DPTs via PGP measurement in a nanomechanical SSH model, overcoming previous experimental challenges.

Findings

DPTs are observed directly through PGP measurement.

DPTs are robust against weak structural disorders.

The method links DPTs with equilibrium phase boundaries.

Abstract

Dynamical phase transitions (DPTs), characterized by non-analytic behaviors in time domain, extend the equilibrium phase transitions to far-from-equilibrium situations. It has been predicted that DPTs can be precisely identified by the discontinuities of the Pancharatnam geometric phase (PGP) during the time evolution. However, PGP always mixes with dynamical phase and the experimental observation of DPTs by PGP is still absent. Here, we theoretically present a novel scheme for eliminating the dynamical phase by taking advantage of chiral symmetry in the Su-Schrieffer-Heeger (SSH) model, and experimentally observe DPTs by directly measuring PGP in a quenched topological nanomechanical lattice. Time-dependent topological structures of the SSH model are configured by eight strong-coupled high-quality-factor nanomechanical oscillators. By measuring the vibration phase and the normalized amplitude of the edge oscillator, we show a direct classical analog of DPTs. Furthermore, we experimentally demonstrate the robustness of DPTs against weak structure disorders, and numerically explore the relation between DPTs and the equilibrium phase boundary. This work not only establishes the quantitative method to identify DPTs, but also opens the door for studying non-equilibrium topological dynamics with a well-controlled nanomechanical system.