First-Order Superradiant Phase Transitions in a Multiqubit Cavity System

We predict the existence of novel first-order phase transitions in a general class of multiqubit cavity systems. Apart from atomic systems, the associated superradiant phase transition should be observable in a variety of solid-state experimental systems, including the technologically important case of interacting quantum dots coupled to an optical cavity mode.

Figure 1

The function $\Omega (x)$, which governs the phase transitions in the system, shown for various values of $J$ and $ϵ$ with $\lambda$ fixed at 1.3. The $y$ axis is shifted for each curve so that all curves are zero at the origin.

Figure 2

Regimes of behavior of the function $\Omega (x)$ which governs the phase transitions in the system. The red broken lines represent various values of $J$ ($J=0.1,0.2,0.3,0.4,0.5,0.6$ from bottom to top). Above the red broken line and to the left of the blue solid line signifies the region where $\Omega (x)$ has two local maxima. Below the red broken line and to the left of the blue solid line signifies the region where $\Omega (x)$ has three local maxima. $\Omega (x)$ has only one maximum to the right of the blue solid line. $\beta$ is taken to be 100.

Figure 3

Plot of the maximizer of the function $\Omega (x)$, which governs the phase transitions in the system, as a function of $J$ and $ϵ$. $\lambda$ and $\beta$ are fixed to 1.3 and 100, respectively.