TEP Seminar - Julian Schmitt

Quantum gases of atoms, exciton-polaritons, and photons provide a test bed for many-body physics under both in- and out-of-equilibrium settings. Experimental control over dimensionality, potentials, or the coupling to reservoirs offers wide possibilities to explore phases of matter, for example, by probing susceptibilities, as the compressibility. For gases of material particles, studies of the mechanical response are well established; for optical quantum gases, they have so far remained elusive. In my talk, I will discuss experimental work demonstrating a measurement of the compressibility of a two-dimensional quantum gas of photons in a box potential inside a dye-filled microcavity, from which we obtain the equation of state for the optical medium. Finally, I will present more recent work observing critical behavior in the spatially uniform quantum gas of light by measurements of the correlations close to the phase transition.

[1]  E. Busley, L. Espert Miranda, A. Redmann, C. Kurtscheid, K. Karkihalli Umesh, F. Vewinger, M. Weitz, and J. Schmitt, Science 375, 1403–1406 (2022)