BCS-BEC quantum phase transition and collective excitations in two-dimensional Fermi gases with p- and d-wave pairings

Abstract

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 $\mu =0$: $E_{\mathbf{k}}\sim k^l$, where $l=1,2$ is the quantum number of the orbital angular momentum. The nonanalyticity of the thermodynamic quantities is 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.

V2: published version

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Cited by in corpus (7)

• Local nodal Cooper pairs in multiorbital systems
• Quantum fluctuations of a resonantly interacting $p$-wave Fermi superfluid in two dimensions
• Resonantly interacting $p$-wave Fermi superfluid in two dimensions: Tan's contact and breathing mode
• Kosterlitz-Thouless transition and vortex-antivortex lattice melting in two-dimensional Fermi gases with $p$- or $d$-wave pairing
• Pairing properties of an odd-frequency superfluid Fermi gas
• Effect of Weak Disorder on the BCS-BEC crossover in a two-dimensional Fermi Gas
• Speed of sound of a spin balanced Fermi gas with s- and d-wave pairings across the BCS-BEC evolution