Ultrafast control of topological transport in quantum materials

J.W. McIver1,2

1Columbia University, Department of Physics, New York, NY, USA

2Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany

Quantum materials exhibit remarkable non-equilibrium phenomena when driven by the strong fields in femtosecond laser pulses. Recent years have seen a surge of interest in using ultrafast light-matter interaction to create and manipulate photon-dressed Floquet-Bloch states as a strategy for controlling material properties. This excitement is fueled by the predictive power of Floquet theory, which has been used, for example, to correctly predict the formation of topological edge modes in periodically-driven systems that exhibit no topological properties in equilibrium. Many of these proposals have been verified in quantum simulation settings, but are only just beginning to be explored in solids.

In this talk, I will present results on the electrical transport properties of quantum materials driven by mid-infrared laser pulses, probed using an ultrafast optoelectronic device architecture. The talk will primarily focus on recent results obtained on the Weyl semimetal Td-MoTe2, where a rectified, helicity-dependent injection current that scales linearly with the applied laser field was observed. This scaling violates the perturbative description of nonlinear optics/transport, which demands a quadratic field scaling for current rectification to occur. The results can be explained using Floquet theory, which predicts that the observed linear scaling arises from the stimulated emission that accompanies the hybridization of Floquet-Bloch states.