Thursday, October 20, 2016 - 3:30pm
Junichiro Kono, Departments of Physics and of Electrical and Computer Engineering, Rice University
Nonperturbative coupling of light with condensed matter in an optical cavity is expected to reveal a host of coherent many-body phenomena and states. In addition, strong coherent light-matter interaction in a solid-state environment is of great interest to emerging quantum-based technologies. However, creating a system that combines a long electronic coherence time, a large dipole moment, and a high cavity quality (Q) factor has been a challenging goal. This talk will describe our recent observation of collective ultrastrong light-matter coupling in an ultrahigh-mobility two-dimensional electron gas (2DEG) in a high-Q terahertz photonic-crystal cavity in a quantizing magnetic field, demonstrating a cooperativity of 360 . The electron cyclotron resonance (CR) peak exhibited splitting into the lower and upper polariton branches with a magnitude that is proportional to the square-root of the 2DEG density, a hallmark of collective vacuum Rabi splitting. Remarkably, the influence of this large splitting can be seen even in a frequency region where the detuning is larger than the resonance frequency itself. Furthermore, a small but definite blue shift was observed for the polariton frequencies due to the normally negligible A^2 term in the light-matter interaction Hamiltonian. Finally, the high-Q cavity suppressed the superradiant decay of coherent CR, which resulted in an unprecedentedly narrow intrinsic CR inewidth of 5.6 GHz at 2 K. These results open up a variety of new possibilities to combine the traditional disciplines of many-body condensed matter physics and cavity-based quantum optics.
October 13, 2016 - 2:39pm