Wide-scale adoption of quantum computing requires building devices in which fragile quantum states are protected from their noisy environments. One approach is based on “symmetry-protected” topological quasiparticles that are theoretically immune to noise.
Such topological control principles are demonstrated using a few-cycle THz pulse to driven coherent Raman phonons and, in turn, induce a topological phase transition in a Dirac semimetal ZrTe5. This is achieved by periodically driving using vibrational coherence of the lattice due to excitation of its lowest Raman-active mode. Above a critical THz pump field threshold, there emerges a long-lived (~100 ps) metastable phase ~100 ps with unique Raman phonon-assisted topological switching dynamics, which is absent for optical pumping.
This quantum control principle is achieved by a mode-selective Raman phonon coherent oscillations, i.e. light-induced atomic motions of Raman symmetry about the equilibrium position. Experimental results combined with first-principles modeling shows that the system transitions from strong to weak topological insulators with a Dirac semimetal phase in-between. The critical atomic displacements are controlled by the phonon coherent pumping. This work opens a new arena of light-wave speed topological electronics and phase transitions controlled by quantum coherence.
C. Vaswani, L.-L. Wang, D.H. Mudiyanselage, Q. Li, P. M. Lozano, G. Gu, D. Cheng, B. Song, L. Luo, R. H. J. Kim, C. Huang, Z. Liu, M. Mootz, I.E. Perakis, Y. Yao, K. M. Ho, and J. Wang “Light-Driven Raman Coherence as a Non-Thermal Route to Ultrafast Topology Switching in a Dirac Semimetal”, Physical Review X, 021013 (2020): https://doi.org/10.1103/PhysRevX.10.021013