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arXiv · 2102.12348

Squeezed-field path-integral description of BCS superconductors

Kazuma Nagao·Dapeng Li·Ludwig Mathey
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Abstract

We develop a squeezed-field path-integral representation for BCS superconductors utilizing a generalized completeness relation of squeezed-fermionic coherent states. We derive a Grassmann path integral of fermionic quasiparticles that explicitly includes the collective degrees of freedom of the order-parameter dynamics governed by the classical Anderson pseudospin model. Based on this method, we analyze the spectral function of the single-particle excitations, and show that the squeezed-field path integral for the BCS Hamiltonian describes a bosonic sideband branch that corresponds to the Higgs amplitude mode of BCS superconductors, in addition to reproducing the quasiparticle and quasihole excitation branches described by the BCS mean-field approximation.

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Kazuma Nagao, Dapeng Li, Ludwig Mathey. 2021-02-24. Squeezed-field path-integral description of BCS superconductors. https://arxiv.org/abs/2102.12348

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