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arXiv · 2004.11459

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

X. Li·K. Yoshioka·Q. Zhang·N. Marquez Peraca·F. Katsutani·W. Gao·G. T. Noe II·J. D. Watson·M. J. Manfra·I. Katayama·J. Takeda·J. Kono
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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 $1s$ 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.

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X. Li, K. Yoshioka, Q. Zhang, N. Marquez Peraca, F. Katsutani, W. Gao, G. T. Noe II, J. D. Watson, M. J. Manfra, I. Katayama, J. Takeda, J. Kono. 2020-04-18. Observation of Photoinduced Terahertz Gain in GaAs Quantum Wells: Evidence for Radiative Two-Exciton-to-Biexciton Scattering. https://doi.org/10.1103/physrevlett.125.167401

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