Higgs mode in a superfluid of Dirac fermions

Article

关键词: COLLECTIVE MODES;    PHASE;    SUPERCONDUCTORS;    FLUCTUATIONS;   

DOI  :  10.1103/PhysRevB.88.014527

来源: SCIE

【 摘 要 】

We study the Higgs amplitude mode in the s-wave superfluid state on the honeycomb lattice inspired by recent cold atom experiments. We consider the attractive Hubbard model and focus on the vicinity of a quantum phase transition between semimetal and superfluid phases. On either side of the transition, we find collective mode excitations that are stable against decay into quasiparticle pairs. In the semimetal phase, the collective modes have Cooperon and exciton character. These modes smoothly evolve across the quantum phase transition, and become the Anderson-Bogoliubov mode and the Higgs mode of the superfluid phase. The collective modes are accommodated within a window in the quasiparticle-pair continuum, which arises as a consequence of the linear Dirac dispersion on the honeycomb lattice, and allows for sharp collective excitations. Bragg scattering can be used to measure these excitations in cold atom experiments, providing a rare example wherein collective modes can be tracked across a quantum phase transition.

【 授权许可】

Free