Determining hot-carrier transport dynamics from terahertz emission
Mohammad Taghinejad, Chenyi Xia, Martin Hrtoň, Kyu‐Tae Lee, Andrew S. Kim, Qitong Li, Burak Güzeltürk, Radek Kalousek, Fenghao Xu, Wenshan Cai, Aaron M. Lindenberg, Mark L. Brongersma
Abstract
Understanding the ultrafast excitation and transport dynamics of plasmon-driven hot carriers is critical to the development of optoelectronics, photochemistry, and solar-energy harvesting. However, the ultrashort time and length scales associated with the behavior of these highly out-of-equilibrium carriers have impaired experimental verification of ab initio quantum theories. Here, we present an approach to studying plasmonic hot-carrier dynamics that analyzes the temporal waveform of coherent terahertz bursts radiated by photo-ejected hot carriers from designer nano-antennas with a broken symmetry. For ballistic carriers ejected from gold antennas, we find an ~11-femtosecond timescale composed of the plasmon lifetime and ballistic transport time. Polarization- and phase-sensitive detection of terahertz fields further grant direct access to their ballistic transport trajectory. Our approach opens explorations of ultrafast carrier dynamics in optically excited nanostructures.