Coherence Control of Directional Nonlinear Photocurrent in Spatially Symmetric Systems

TL;DR

This paper demonstrates that centrosymmetric materials can generate bulk photovoltaic currents through coherent phonon excitation, revealing new ways to control nonlinear optical responses involving spin and orbital degrees of freedom.

Contribution

It introduces a novel mechanism for bulk photovoltaic effects in symmetric materials via coherent phonons, expanding the understanding of light-matter interactions.

Findings

Generation of unidirectional static electric current in centrosymmetric materials

Observation of terahertz alternating currents driven by coherent phonons

Extension of injection charge current to include spin and orbital angular momentum

Abstract

The interplay between crystal symmetry and its optical responses is at the heart of tremendous recent advances in light-matter interactions and applications. Nonlinear optical processes that produce electric currents, for example bulk photovoltaic (BPV) effect, require inversion symmetry broken materials, such as ferroelectrics. In the current work, we demonstrate that such BPV current could be generated in centrosymmetric materials with excitation of out-of-equilibrium coherent phonons. This is much different from the generally studied static or thermally excited states. We show that depending on the oscillating phase factor of the coherent phonon, uni-directional static electric current can be observed, in addition to some terahertz alternating currents. We also generalize the conventional injection charge current into angular momentum (spin and orbital) degrees of freedom, and demonstrate spin and orbital BPV photocurrents under coherent phonons. Our findings open the pathway to exploring the exotic phonon-photon-electron coherent interactions in quantum materials.