Abstract
We demonstrate how the properties of light-induced electronic Floquet states in solids impact natural physical observables, such as transport properties, by capturing the environmental influence on the electrons. We include the environment as dissipative processes, such as inter-band decay and dephasing, often ignored in Floquet predictions. These dissipative processes determine the Floquet band occupations of the emergent steady state, by balancing out the optical driving force. In order to benchmark and illustrate our framework for Floquet physics in a realistic solid, we consider the light-induced Hall conductivity in graphene recently reported by J.~W.~McIver, et al., Nature Physics (2020). We show that the Hall conductivity is estimated by the Berry flux of the occupied states of the light-induced Floquet bands, in addition to the kinetic contribution given by the average band velocity. Hence, Floquet theory provides an interpretation of this Hall conductivity as a geometric-dissipative effect. We demonstrate this mechanism within a master equation formalism, and obtain good quantitative agreement with the experimentally measured Hall conductivity, underscoring the validity of this approach which establishes a broadly applicable framework for the understanding of ultrafast non-equilibrium dynamics in solids.
Highlights
INTRODUCTIONWhile the established approach to solid state physics is to probe equilibrium or near-equilibrium properties of a given material, we take a more active stance, to design nonequilibrium states with desired properties by periodic driving
Light control of matter has emerged as a new chapter of condensed matter physics
We show that the Hall conductivity is estimated by the Berry flux of the occupied states of the light-induced Floquet bands, in addition to the kinetic contribution given by the average band velocity
Summary
While the established approach to solid state physics is to probe equilibrium or near-equilibrium properties of a given material, we take a more active stance, to design nonequilibrium states with desired properties by periodic driving This new vantage point is reflected in recent experimental work on light-controlled superconductivity References [17,18,19,20,21] have proposed to illuminate graphene with circularly polarized light with the purpose of inducing a topologically insulating state [22,23,24,25,26], with the same low-energy behavior as the Haldane model [27] We note that these proposed experiments would only reproduce the behavior of the Haldane model in a band insulating state, under the above-mentioned assumption of a large driving frequency. Theoretical studies on dissipative dynamics in graphene have been reported in Refs. [33,34,35]
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