Phat Nguyen, Monash
Ultra-fast photocurrents and dynamic conductivity have been utilized as multiphysics diagnostic tools for various quantum materials. A complete understanding of the dynamic conductivity in graphene across a wide frequency range is required for the development of modern electronic and optoelectronic devices. In this study, we use terahertz time-domain spectroscopy to measure the complex dynamic electrical conductivity of graphene deposited on a SiO2/Si substrate at room temperature as a function of charge carrier density. In the THz frequency domain, the conductivity of heavily doped graphene generally follows the conventional Drude model with predominating intraband processes.
Our experimental results reveal a significant deviation from the Drude-type spectral response around the charge neutrality point. To better elucidate the observed conductivity, we propose a model based on quantum kinetic equations and density matrix theory. This model accounts for the scatterings that occur on a vector potential, which is in turn generated by the pseudo-magnetic field resulting from deformations in graphene. Our findings demonstrate how Dirac electron scatterings on the pseudo-magnetic field influence the conductivity spectra of graphene around the charge-neutrality point at room temperature.
About the presenter
Phat Tan Nguyen is a PhD student working under the supervision of A/Prof Agustin Schiffrin and Dr Gary Beane at Monash University, where he is investigating optically-driven topological phases of matter using terahertz time-domain spectroscopy and pump-probe spectroscopy with sub-picosecond time resolution, and at the scale of a single atom. He is mainly involved in Research theme 1: topological materials and Research theme 3: light-transformed materials.