Light-Driven Raman Coherence as a Non-Thermal Route to Ultrafast Topology Switching

TL;DR

This paper demonstrates a non-thermal, light-driven method to induce ultrafast topological phase transitions in Dirac materials using vibrational coherence, revealing new pathways for quantum control and potential quantum information applications.

Contribution

It introduces a THz pulse technique that leverages Raman-active phonons to control topological phases dynamically, a novel approach compared to traditional optical methods.

Findings

Observation of a long-lived metastable phase induced by vibrational coherence

Identification of a mode-selective Raman coupling driving topological transitions

Spectral and relaxation features indicating non-thermal control of topological states

Abstract

A grand challenge underlies the entire field of topology-enabled quantum logic and information science: how to establish topological control principles driven by quantum coherence and understand the time-dependence of such periodic driving? Here we demonstrate a THz pulse-induced phase transition in Dirac materials that is periodically driven by vibrational coherence due to excitation of the lowest Raman-active mode. Above a critical field threshold, there emerges a long-lived metastable phase with unique Raman coherent phonon-assisted switching dynamics, absent for optical pumping. The switching also manifest itself by non-thermal spectral shape, relaxation slowing down near the Lifshitz transition where the critical Dirac point (DP) occurs, and diminishing signals at the same temperature that the Berry curvature induced Anomalous Hall Effect varnishes. These results, together with first-principles modeling, identify a mode-selective Raman coupling that drives the system from strong to weak topological insulators, STI to WTI, with a Dirac semimetal phase established at a critical atomic displacement controlled by the phonon pumping. Harnessing of vibrational coherence can be extended to steer symmetry-breaking transitions, i.e., Dirac to Weyl ones, with implications on THz topological quantum gate and error correction applications.