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HL: Fachverband Halbleiterphysik

HL 52: THz and MIR Physics in Semiconductors

HL 52.4: Vortrag

Freitag, 13. März 2026, 10:15–10:30, POT/0006

Elucidating carrier dynamics in bismuth thin film with time-resolved terahertz spectroscopy — •Gurivireddy Yettapu, Fabian Thiemann, Michael Horn-von Hoegen, and Martin Mittendorff — University of Duisburg-Essen, Duisburg, Germany

Bismuth (Bi) is a Peierls distorted semimetal in its bulk state that transforms into a semiconductor for thicknesses below ~30 nm [1]. Time-resolved terahertz spectroscopy is an ideal tool to investigate the charge carrier dynamics by following the pump-induced change in electric field with pump-probe delay. Herein, we employed optical-pump terahertz-probe spectroscopy to elucidate the carrier dynamics in single crystalline Bi film with a thickness ~36 nm, including spectrally resolved measurements to determine the frequency dependent complex conductivity. At a pump fluence of 30 uJ/cm2, we observe a pump-induced change of the electric field of about 20 %, followed by an exponential decay with a relaxation time of ~7 ps. Our results reveal that carrier relaxation times are hardly affected by the pump fluence, the complex conductivity can be well described by the Drude model. Our future studies include thickness- and temperature-dependent measurements to gain insights about the carrier-lattice interactions in the semiconductor and semimetal phase. [1] C. A. Hoffman et al., Phys. Rev. B. 48, 11431-11434 (1993).

Keywords: Bismuth; Drude; Time-resolved; Terahertz; Spectroscopy