Higgs Amplitude Modes, Goldstone Modes, Pair Density Waves

by Tommy on 9/03/2017

And of course Eduardo Fradkin et al., at the University of Illinois Urbana-Champaign rocks.

Check out this study. They’re doing quantum cosmology and they don’t even know it!


Higgs Modes in the Pair Density Wave Superconducting State, Rodrigo Soto-Garrido, Yuxuan Wang, Eduardo Fradkin and S. Lance Cooper (7 March 2017)

The pair density wave (PDW) superconducting state has been proposed to explain the layer- decoupling effect observed in the compound La2−xBaxCuO4 at x = 1/8 (Phys. Rev. Lett. 99, 127003). In this state the superconducting order parameter is spatially modulated, in contrast with the usual superconducting (SC) state where the order parameter is uniform. In this work, we study the properties of the amplitude (Higgs) modes in a unidirectional PDW state. To this end we consider a phenomenological model of PDW type states coupled to a Fermi surface of fermionic quasiparticles. In contrast to conventional superconductors that have a single Higgs mode, unidirectional PDW superconductors have two Higgs modes. While in the PDW state the Fermi surface largely remains gapless, we find that the damping of the PDW Higgs modes into fermionic quasiparticles requires exceeding an energy threshold. We show that this suppression of damping in the PDW state is due to kinematics. As a result, only one of the two Higgs modes is significantly damped. In addition, motivated by the experimental phase diagram, we discuss the mixing of Higgs modes in the coexistence regime of the PDW and uniform SC states. These results should be observable directly in a Raman spectroscopy, in momentum resolved electron energy loss spectroscopy, and in resonant inelastic X-ray scattering, thus providing evidence of the PDW states.

You need to read this paper because this is as good as it gets nowadays.


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