arXiv subjects

Tsan Huang

Publications and source records attributed to Tsan Huang.

3 recordsLinked to original sources

arXiv2026

Floquet polaritons in optically driven materials

Polaritons are coupled collective modes of light and matter in quantum materials. In modern pump-probe experiments, a pump light pulse may dramatically alter the properties of the polaritons, rendering them Floquet polaritons that can be detected by a probe pulse. We present a practical framework to describe Floquet polaritons in terms of the linear and nonlinear optical properties of the material. The central quantity that yields the spectra of Floquet polaritons is an effective linear optical susceptibility contributed by the pump through nonlinear optical susceptibilities. We apply this method to graphene and show that via its third-order optical nonlinearity, infrared pump leads to Floquet plasmon bands. Notably, near plasmonic band crossings, parametric instability leads to flat bands with unstable modes and exceptional points that closely resemble those of non-Hermitian systems. As a second example, we show that in hexagonal boron nitride pumped by mid-infrared laser, the pump induces Floquet phonon polariton bands via phononic nonlinearity, which can be detected with either far-field or near-field optical technique. Finally, in layered superconductors pumped by THz light polarized along the out-of-plane direction, the Josephson-type optical nonlinearity leads to Floquet Josephson plasmons, which manifest as new peaks in the THz reflectivity of a probe pulse.

cond-mat.mes-hall↗

arXiv2025

Universal Phase Transitions of Matter in Optically Driven Cavities

Optical cavities have been widely applied to manipulate the properties of solid state materials inside them. We propose that in systems embedded within optical cavities driven by incident pump light, the pump induces generic phase transitions into new nonequilibrium steady states. This effect arises from the ponderomotive potential, the effective static potential exerted by the pump on the low energy degrees of freedom, which exhibits a universal steplike structure that pushes the matter degrees of freedom in the direction that redshifts the cavity photon modes. For a two dimensional electron liquid in a driven cavity, this steplike potential pushes the electron density to jump to a smaller value so that a hybrid cavity photon mode is redshifted to slightly below the pump frequency. Similarly, for a dirty superconductor in such a driven cavity, this potential acts on the superconducting order parameter and causes a first order phase transition to a new steady state with a smaller gap. By realistic electromagnetic modeling of the cavity that includes all cavity modes, we construct the nonequilibrium phase diagrams for experimentally relevant devices.

cond-mat.mes-hall↗

arXiv2025

Interaction effects on electronic Floquet spectra: Excitonic effects

Floquet engineering of electronic states by light is a central topic in modern experiments. However, the impact of many-body interactions on the single-electron properties remains unclear in this non-equilibrium situation. We propose that interaction effects could be reasonably understood by performing perturbative expansion in both the pump field and the electron-electron interaction when computing physical quantities. As an example, we apply this approach to semiconductors and show analytically that excitonic effects, i.e., effects of electron-hole interaction, lead to dramatic corrections to the single-electron Floquet spectra even when the excitons are only virtually excited by the pump light. We compute these effects in phosphorene and monolayer MoS$_2$ for time- and angle-resolved photoemission spectroscopy and ultrafast optical experiments.

cond-mat.other↗