Speaker
Description
Two-dimensional materials offer a versatile platform for nonlinear optoelectronics, where light can generate electrical currents and optical signals that are strongly tunable, symmetry-sensitive, and intrinsically linked to the microscopic dynamics of electrons. In contrast to conventional photodetection, nonlinear photocurrent generation can provide direct access to electronic structure, collective motion, nonequilibrium carrier dynamics, and energy flow in quantum materials.
In this talk, I will present a broad, non-technical overview of nonlinear optical and optoelectronic phenomena in two-dimensional systems, with emphasis on their physical principles and potential device relevance. I will first highlight selected examples of nonlinear optics in graphene and related materials, including electrically tunable harmonic generation and ultrafast optical control. I will then introduce two central mechanisms of photocurrent generation: shift current, associated with real-space charge displacement during optical excitation, and injection current, arising from the asymmetric population of photoexcited carriers. These mechanisms illustrate how material symmetry and band geometry can convert light directly into directed electrical motion.
The second part of the talk will focus on emerging regimes beyond standard single-particle descriptions. I will discuss hydrodynamic and plasmon-assisted photodetection, where collective electron motion can enhance and shape the nonlinear electrical response, as well as light-induced thermoelectric effects, where optical heating and nonequilibrium energy relaxation generate photocurrents. Together, these examples show that nonlinear photocurrent measurements are not only relevant for ultrafast and tunable photodetectors, but also provide a sensitive probe of collective, geometric, and thermal electronic processes in low-dimensional materials.
The talk aims to provide an accessible perspective on nonlinear photocurrent generation as a bridge between fundamental condensed matter physics and future optoelectronic and photodetection technologies based on two-dimensional quantum materials.