Symmetry governs the properties of every crystalline material with time-reversal symmetry, playing an important role for both conventional and topological states of matter. This makes the ability to optically control symmetry on ultrafast timescales a critical step in future applications such as a topological transistor, which relies on the ability to switch between different topological phases. Previous works have achieved such control by directly exciting vibrational modes in a crystal, which requires intense, ultrashort infrared (IR) pulses. In contrast, we here demonstrate an all-electronic mechanism relying on photocurrents that offers a new way of tuning symmetry in quantum materials using ultrashort near-IR pulses. We explicitly break magnetic symmetries including time-reversal symmetry in the Weyl semimetal TaAs by inducing large photocurrents away from high-symmetry directions. The resulting transient symmetry changes were sensitively detected with time-resolved second harmonic generation. Finally, we control the degree of symmetry breaking via the polarization of the optical driving pulses, which sets the photocurrent direction. This general approach for optically breaking symmetry should apply to other classes of quantum materials, and could thus be used to optically control symmetry in a variety of systems on ultrafast timescales and ultimately drive phase transitions between symmetry-protected states.
“Photocurrent-driven transient symmetry breaking in the Weyl semimetal TaAs”, N Sirica, P. P. Orth, M. S. Scheurer, Y.M. Dai, M.-C. Lee, P. Padmanabhan, L.T. Mix, S.W. Teitelbaum, M. Trigo, L.X. Zhao, G.F. Chen, B. Xu, R. Yang, B. Shen, C.-C. Lee, H. Lin, T.A. Cochran, S.A. Trugman, J.-X. Zhu, M.Z. Hasan, N. Ni, X.G. Qiu, A.J. Taylor, D.A. Yarotski, R.P. Prasankumar. Nat. Mater. 21, 62 (2022).