Observation of Photoinduced Terahertz Gain in GaAs Quantum Wells: Evidence for Radiative Two-Exciton-to-Biexciton Scattering

Xinwei Li, Katsumasa Yoshioka, Qi Zhang, Nicolas Marquez Peraca, Fumiya Katsutani, Weilu Gao, G. Timothy Noe, II, John D. Watson, Michael J. Manfra, Ikufumi Katayama, Jun Takeda, and Junichiro Kono

Phys. Rev. Lett. 125, 167401 – Published 16 October 2020

Abstract

We have observed photoinduced negative optical conductivity, or gain, in the terahertz frequency range in a GaAs multiple-quantum-well structure in a strong perpendicular magnetic field at low temperatures. The gain is narrow band: it appears as a sharp peak (linewidth $< 0.45 meV$ ) whose frequency shifts with applied magnetic field. The gain has a circular-polarization selection rule: a strong line is observed for hole-cyclotron-resonance-active polarization. Furthermore, the gain appears only when the exciton $1 s$ state is populated, which rules out intraexcitonic transitions to be its origin. Based on these observations, we propose a possible process in which the stimulated emission of a terahertz photon occurs while two free excitons scatter into one biexciton in an energy and angular-momentum conserving manner.

Received 18 April 2020
Revised 19 June 2020
Accepted 16 September 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.167401

Physics Subject Headings (PhySH)

Biexcitons Excitons Optical conductivity Photoinduced effect

III-V semiconductors Quantum wells

Photoluminescence Terahertz spectroscopy

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Xinwei Li ^1,*, Katsumasa Yoshioka^2,*, Qi Zhang³, Nicolas Marquez Peraca⁴, Fumiya Katsutani¹, Weilu Gao¹, G. Timothy Noe, II¹, John D. Watson⁵, Michael J. Manfra⁵, Ikufumi Katayama ², Jun Takeda ², and Junichiro Kono ^1,4,6,†

¹Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005, USA
²Department of Physics, Graduate School of Engineering Science, Yokohama National University, Yokohama 240-8501, Japan
³School of Physics, Nanjing University, Nanjing 210093, China
⁴Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
⁵Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
⁶Department of Material Science and NanoEngineering, Rice University, Houston, Texas 77005, USA

^*These authors contributed equally to this work.
^†kono@rice.edu

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Vol. 125, Iss. 16 — 16 October 2020

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