Collective non-perturbative coupling of 2D electrons with high-quality-factor terahertz cavity photons

• Published in: Nature physics Vol. 12; no. 11; pp. 1005 - 1011
• Main Authors: Zhang, Qi, Lou, Minhan, Li, Xinwei, Reno, John L, Pan, Wei, Watson, John D, Manfra, Michael J, Kono, Junichiro
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 01.11.2016
• Subjects: Atoms & subatomic particles; Cyclotron resonance; Decay; Electron gas; Electronics; Holes; Magnetic fields; Magnetic resonance; Optics; Photons; Quantum physics; Splitting
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys3850

The collective interaction of electrons with light in a high-quality-factor cavity is expected to reveal new quantum phenomena1, 2, 3, 4, 5, 6, 7 and find applications in quantum-enabled technologies8, 9. However, combining a long electronic coherence time, a large dipole moment, and a high quality-factor has proved difficult10, 11, 12, 13. Here, we achieved these conditions simultaneously in a two-dimensional electron gas in a high-quality-factor terahertz cavity in a magnetic field. The vacuum Rabi splitting of cyclotron resonance exhibited a square-root dependence on the electron density, evidencing collective interaction. This splitting extended even where the detuning is larger than the resonance frequency. Furthermore, we observed a peak shift due to the normally negligible diamagnetic term in the Hamiltonian. Finally, the high-quality-factor cavity suppressed superradiant cyclotron resonance decay, revealing a narrow intrinsic linewidth of 5.6 GHz. High-quality-factor terahertz cavities will enable new experiments bridging the traditional disciplines of condensed-matter physics and cavity-based quantum optics.