Stability of High-Density Two-Dimensional Excitons against a Mott Transition in High Magnetic Fields Probed by Coherent Terahertz Spectroscopy

Abstract

We have performed time-resolved terahertz absorption measurements on photoexcited electron-hole pairs in undoped GaAs quantum wells in magnetic fields. We probed both unbound- and bound-carrier responses via cyclotron resonance and intraexciton resonance, respectively. The stability of excitons, monitored as the pair density was systematically increased, was found to dramatically increase with increasing magnetic field. Specifically, the 1$s$-2$p_{-}$ intraexciton transition at 9 T persisted up to the highest density, whereas the 1$s$-2$p$ feature at 0 T was quickly replaced by a free-carrier Drude response. Interestingly, at 9 T, the 1$s$-2$p_{-}$ peak was replaced by free-hole cyclotron resonance at high temperatures, indicating that 2D magnetoexcitons do dissociate under thermal excitation, even though they are stable against a density-driven Mott transition.

5 pages, 4 figures

References in corpus (4)

• Broadband THz study of excitonic resonances in the high-density regime
• Ultrafast terahertz probes of interacting dark excitons in chirality-specific semiconducting single-walled carbon nanotubes
• Observation of Coulomb-Assisted Dipole-Forbidden Intraexciton Transitions in Semiconductors
• Transient terahertz spectroscopy of excitons and unbound carriers in quasi two-dimensional electron-hole gases

Cited by in corpus (8)

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• Time-Domain Terahertz Spectroscopy in High Magnetic Fields
• A Hubbard exciton fluid in a photo-doped antiferromagnetic Mott insulator
• Hot electron cooling in InSb probed by ultrafast time-resolved terahertz cyclotron resonance
• Transient transition from free carrier metallic state to exciton insulating state in GaAs by ultrafast photoexcitation
• Observation of Photoinduced Terahertz Gain in GaAs Quantum Wells: Evidence for Radiative Two-Exciton-to-Biexciton Scattering
• Observation of excitons bound by antiferromagnetic correlations
• Distinct terahertz third-harmonic generation of many-body excitonic states