Gaoqing Cao, Lianyi He, Pengfei Zhuang
It is generally believed that the BCS-BEC evolution in fermionic systems with s-wave pairing is a smooth crossover. However, for nonzero orbital-angular-momentum pairing such as p- or d-wave pairing, the system undergoes a quantum phase transition at the point where the chemical potential $\mu$ vanishes. In this paper, we study the BCS-BEC quantum phase transition and the collective excitations associated with the order-parameter fluctuations in two-dimensional fermionic systems with p- and d-wave pairings. We show that the quantum phase transition in such systems can be generically traced back to the infrared behavior of the fermionic excitation at $\mu=0$: $E_k \sim k^l$, where $l=1,2$ is the quantum number of the orbital angular momentum. The nonanalyticities of the thermodynamic quantities are due to the infrared divergence caused by the fermionic excitation at $\mu=0$. As a result, the evolution of the Anderson-Bogoliubov mode is not smooth: its velocity is nonanalytical across the quantum phase transition.
View original:
http://arxiv.org/abs/1211.2470
No comments:
Post a Comment