Goldstone mode and pair-breaking excitations in atomic Fermi superfluids
Abstract
Spontaneous symmetry breaking is a central paradigm of elementary particle physics, magnetism, superfluidity and superconductivity. According to Goldstone's theorem, phase transitions that break continuous symmetries lead to the existence of gapless excitations in the long-wavelength limit. These Goldstone modes generally dominate the low-energy excitations, showing that symmetry breaking has a profound impact on the physical properties of matter. Here, we present the first comprehensive study of the elementary excitations in a homogeneous strongly interacting Fermi gas through the crossover from a Bardeen-Cooper-Schrieffer (BCS) superfluid to a Bose-Einstein condensate (BEC) of molecules using two-photon Bragg spectroscopy. The spectra exhibit a discrete Goldstone mode, associated with the broken symmetry superfluid phase, as well as pair breaking single-particle excitations. Our techniques yield a direct determination of the superfluid pairing gap and speed of sound in close agreement with a strong-coupling theory.
Cite
@article{arxiv.1707.00406,
title = {Goldstone mode and pair-breaking excitations in atomic Fermi superfluids},
author = {Sascha Hoinka and Paul Dyke and Marcus G. Lingham and Jami J. Kinnunen and Georg M. Bruun and Chris J. Vale},
journal= {arXiv preprint arXiv:1707.00406},
year = {2017}
}
Comments
Original version, full text published online in Nature Physics