Switching Topological Phases in Quantum Materials by Phonons

Zirconium pentatelluride (ZrTe₅) is a material at the phase boundary between topological insulator and Dirac semimetal. It was shown theoretically that atomic displacements corresponding to five of the six zone-center A_g (symmetry-preserving) phonon modes can drive a topological transition from a strong to a weak topological insulator with a Dirac semimetal state emerging at the transition.¹ Experimentally, a few-cycle THz-pulse-induced phase transition was demonstrated by the excitation of the lowest Raman active mode.² 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. Using first-principles and effective Hamiltonian methods, it is shown that lattice distortions corresponding to all three types of zone-center infrared optical phonon modes can drive the system from a topological insulator to a Weyl semimetal.³ Experimentally, the light induced switching to Weyl phase was dynamically created by B_1u phonons that led to helicity-dependent current, orthogonal to the dynamical inversion symmetry breaking axis, via circular photogalvanic effect. Such phononic control breaks ground for coherent manipulation of Weyl nodes and robust quantum transport without application of static electric or magnetic fields, which is desirable for high-temperature fault-tolerant multi-qubit computation and communication.<br/><br/>The work at Brookhaven National Laboratory was supported by the U.S. Department of Energy (DOE) the Office of Basic Energy Sciences, Materials Sciences, and Engineering Division under Contract No. DESC0012704.<br/><br/>References:<br/><br/>1) N. Aryal et al, Phys. Rev. Lett. 126, 016401 (2021)<br/>2) C. Vaswani et al Phys. Rev. X 10, 021013 (2020)<br/>3) N. Aryal et al, npj Computational Materials 8, 113 (2022)<br/>4) L. Luo et al, Nature Materials 20, 329 (2021)