CMT151

Bosonic Surface States and Acoustic Spectroscopy of Confined Superfluid ³He-B

• Author(s): Takeshi Mizushima and J. A. Sauls
• Address: Department of Physics & Astronomy, Northwestern University, Evanston, IL 60208
• Date: January 8, 2018
• Journal: Physical Review Letters, submitted [DOI] [PDF]
• Abstract: Using an effective field theory we study the low-lying bosonic excitations and their couplings to phonons at ultrasonic frequencies in superfluid ³He-B under strong confinement. We show that confinement induces a rich spectrum of low-lying bosons, including surface-bound bosonic states, as well as fine structure of long-lived massive bosons. Under sufficiently strong confinement we find a dynamical instability of the ³He-B film: the frequency of the surface-bound boson softens at finite wavevector, then develops a pole in the upper half of the complex frequency plane, signalling a dynamical instability of the translationally invariant superfluid vacuum towards pair-density-wave "crystallization". We discuss the signatures and observability of the low-lying bosonic spectrum based on analysis of the ultrasound attenuation from resonant excitation of the bosonic modes. We also note that surface-bound bosonic modes are not unique to ³He-B, but are expected to be common to unconventional superconductors with a multi-component order parameter.

• Comment: 5 pages, 5 figures

• Eprint: [PDF] [arXiv]

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