Light-Driven Raman Coherence as a Nonthermal Route to Ultrafast Topology Switching in a Dirac Semimetal

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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 few-cycle THz-pulse-induced phase transition in a Dirac semimetal ZrTe5 that is periodically driven by vibrational coherence due to excitation of the lowest Raman active mode. Above a critical THz-pump field threshold, there emerges a long-lived metastable phase, approximately 100 ps, with unique Raman phonon-assisted topological switching dynamics absent for optical pumping. The switching also manifests itself by distinct features: nonthermal spectral shape, relaxation slowing near the Lifshitz transition where the critical Dirac point occurs, and diminishing signals at the same temperature that the Berry-curvature-induced anomalous Hall effect magnetoresistance vanishes. These results, together with first-principles modeling, identify a mode-selective Raman coupling that drives the system from strong to weak topological insulators with a Dirac semimetal phase established at a critical atomic displacement controlled by the phonon coherent pumping. Harnessing of vibrational coherence can be extended to steer symmetry-breaking transitions, i.e., Dirac to Weyl ones, with implications for THz topological quantum gate and error correction applications.

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Vaswani, C., Wang, L. L., Mudiyanselage, D. H., Li, Q., Lozano, P. M., Gu, G. D., … Wang, J. (2020). Light-Driven Raman Coherence as a Nonthermal Route to Ultrafast Topology Switching in a Dirac Semimetal. Physical Review X, 10(2). https://doi.org/10.1103/PhysRevX.10.021013

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