Light-induced emergent phenomena in 2D materials and topological materials

Abstract

Light–matter interaction in 2D and topological materials provides a fascinating control knob for inducing emergent, non-equilibrium properties and achieving new functionalities in the ultrafast timescale (from femtosecond to picosecond). Over the past decade, intriguing light-induced phenomena, such as Bloch–Floquet states and photo-induced phase transitions, have been reported experimentally, but many still await experimental realization. In this Review, we discuss recent progress on the light-induced phenomena, in which the light field could act as a time-periodic field to drive Floquet states, induce structural and topological phase transitions in quantum materials, couple with spin and various pseudospins, and induce nonlinear optical responses that are affected by the geometric phase. Perspectives on the opportunities of proposed light-induced phenomena, as well as open experimental challenges, are also discussed. Light–matter interaction in 2D and topological materials provides a fascinating control knob for inducing emergent, non-equilibrium properties and achieving new functionalities in the ultrafast timescale. This Review discusses recent experimental progress on the light-induced phenomena and provides perspectives on the opportunities of proposed light-induced phenomena, as well as open experimental challenges. Light–matter interaction plays critical roles in emerging exotic phenomena in 2D materials and topological materials not only as an experimental probe but also as a control knob for inducing emergent non-equilibrium properties that are otherwise not possible to be achieved in the equilibrium state. Light, regarded as a time-periodic electric field, can induce the photo-dressing Floquet states, which can be further utilized to dynamically engineer the electronic properties of quantum materials, especially topological properties, dubbed Floquet engineering. By resonantly exciting electrons or lattices, light–matter interaction can dynamically change the energy landscape of 2D and topological materials, leading to the light-induced phase transitions, such as the emergence of light-induced superconductivity or hidden states. By coupling the angular momentum of light with spins and pseudospins, light–matter interaction can be used to detect and manipulate various quantum degrees of freedom for new concepts of device applications. By coupling to geometric phase of the Bloch wavefunctions, light–matter interaction can be used as a powerful probe of geometric-phase-related properties and to manipulate the material’s response, leading to rich, nonlinear optical responses.