Frustrated Superradiant Phase Transition

TL;DR

This paper introduces the concept of a frustrated superradiant phase transition in cavity QED systems, revealing unique critical behaviors and symmetry breaking due to geometric frustration in light-matter interactions.

Contribution

It demonstrates the occurrence of frustrated superradiant phases in a Dicke trimer model with both positive and negative photon hopping energies, uncovering novel critical exponents and symmetry-breaking phenomena.

Findings

Identification of a six-fold degenerate ground state in frustrated superradiance.

Discovery of coexisting diverging time and fluctuation scales with different critical exponents.

Proposal of experimental probes based on site-dependent photon number critical exponents.

Abstract

Frustration occurs when a system cannot find a lowest-energy configuration due to conflicting constraints. We show that a frustrated superradiant phase transition occurs when the ground-state superradiance of cavity fields due to local light-matter interactions cannot simultaneously minimize the positive photon hopping energies. We solve the Dicke trimer model on a triangle motif with both negative and positive hopping energies and show that the latter results in a six-fold degenerate ground-state manifold in which the translational symmetry is spontaneously broken. In the frustrated superradiant phase, we find that two sets of diverging time and fluctuation scales coexist, one governed by the mean-field critical exponent and another by a novel critical exponent. The latter is associated with the fluctuation in the difference of local order parameters and gives rise to site-dependent photon number critical exponents, which may serve as an experimental probe for the frustrated superradiant phase. We provide a qualitative explanation for the emergence of unconventional critical scalings and demonstrate that they are generic properties of the frustrated superradiant phase at the hand of a one-dimensional Dicke lattice with an odd number of sites. The mechanism for the frustrated superradiant phase transition discovered here applies to any lattice geometries where the anti-ferromagnetic ordering of neighboring sites are incompatible and therefore our work paves the way towards the exploration of frustrated phases of coupled light and matter.