VIRTUAL COLLOQUIUM ONLY
Recent experiments have demonstrated that light and matter (and also matter and matter) can mix together to an extreme degree, and previously uncharted regimes are currently being explored . This talk will summarize a series of experiments we have recently performed in such regimes [2-6]. We will first describe our observation of ultrastrong light-matter coupling in a 2D electron gas in a terahertz cavity in a magnetic field, demonstrating a record-high cooperativity . The observed vacuum Rabi splitting was proportional to the square-root of the electron density, a hallmark of Dicke cooperativity, accompanied by a vacuum Bloch-Siegert shift . We also studied microcavity exciton polaritons in an aligned carbon nanotube film , which exhibited polarization-dependent cooperative ultrastrong coupling . Finally, we have generalized the concept of Dicke cooperativity to magnetism in the form of resonant spin-magnon coupling . Our results provide a route for understanding, controlling, and predicting novel phases of condensed matter using concepts and tools available in quantum optics.
1. Forn-Díaz, L. Lamata, E. Rico, J. Kono, and E. Solano, Reviews of Modern Physics 91, 025005 (2019).
2. Zhang et al., Nature Physics 12, 1005 (2016).
3. Li et al., Nature Photonics 12, 324 (2018).
4. He et al., Nature Nanotechnology 11, 633 (2016).
5. Gao et al., Nature Photonics 12, 362 (2018).
6. Li et al., Science 361, 794 (2018).