Dilute two dimensional interacting quantum fluids

William J. Mullin, Markus Holzmann, Franck Laloë

G. Gervais

E. J. Melé

A quasiparticle description of the hole doped "short range" RVB state is developed and it is applied to study the ground state properties of the interacting many holon fluid. The model is based on the conjecture that the elementary charged excitation of the RVB state, the holon, corresponds to an quantized vortex in a condensed quantum fluid of mobile singlets. The doped RVB state is described as a two component fluid of these quasiparticles with repulsive electrostatic interparticle interactions and an effective U(1) gauge field coupling the motion of these objects to the condensed particles of the parent RVB fluid. In this model for the doped state we find: (1) Quantum commensurability effects in the doped state, similar to those encountered in the fractional quantum Hall problem, lead to phase segregation of a doped state which corresponds to a 20% dilution of the doped antiferromagnet. (2) The ground state of the interacting holon fluid at this density is found to exhibit off diagonal long range order, describing a two-dimensional pairing condensation of the holons.

Rajinder M. Kumar

R. Y. Chiao, T. H. Hansson, Jon Magne Leinaas +1 more

We formulate an effective theory for the atom-mediated photon-photon interactions in a two-dimensional ``photon fluid'' confined in a Fabry-P\'erot resonator. With the atoms modeled by a collection of anharmonic Lorentz oscillators, the effective interaction is evaluated to second order in the coupling constant (the anharmonicity parameter). The interaction has the form of a renormalized two-dimensional delta-function potential, with the renormalization scale determined by the physical parameters of the system, such as density of atoms and the detuning of the photons relative to the resonance frequency of the atoms. For realistic values of the parameters, the perturbation series has to be resummed, and the effective interaction becomes independent of the ``bare'' strength of the anharmonic term. The resulting expression for the nonlinear Kerr susceptibility is parametrically equal to the one found earlier for a dilute gas of two-level atoms. Using our result for the effective interaction parameter, we derive conditions for the formation of a photon fluid, both for Rydberg atoms in a microwave cavity and for alkali atoms in an optical cavity.

Jelena Stajic

Quantum Fluids In recent years, quantum fluids have been studied largely in gaseous form, such as the Bose-Einstein condensates (BECs) of alkali atoms and related species. Quantum liquids, other than liquid helium, have been comparatively more difficult to come by. Cabrera et al. combined two BECs and manipulated the atomic interactions to create droplets of a quantum liquid (see the Perspective by Ferrier-Barbut and Pfau). Because the interactions were not directional, the droplets had a roughly round shape. The simplicity of this dilute system makes it amenable to theoretical modeling, enabling a better understanding of quantum fluids. Science , this issue p. [301][1]; see also p. [274][2] [1]: /lookup/doi/10.1126/science.aao5686 [2]: /lookup/doi/10.1126/science.aar3785