Critical Ultrasonics Near the Superfluid Transition : Finite Size Effects

TL;DR

This paper investigates how finite size effects near the superfluid transition influence ultrasonic attenuation, showing that ultrasonic measurements are highly sensitive to boundary-induced fluctuations, especially above the lambda point.

Contribution

It provides explicit calculations of the first deviation in ultrasonic attenuation due to finite size effects near the superfluid transition, highlighting ultrasonic methods as effective probes.

Findings

Ultrasonic attenuation is suppressed below bulk values near the transition.

Finite size effects cause larger deviations in ultrasonic attenuation than in static thermodynamic quantities.

Ultrasonics are highly effective for detecting finite size effects in superfluid systems.

Abstract

The suppression of order parameter fluctuations at the boundaries causes the ultrasonic attenuation near the superfluid transition to be lowered below the bulk value. We calculate explicitly the first deviation from the bulk value for temperatures above the lambda point. This deviation is significantly larger than for static quantities like the thermodynamic specific heat or other transport properties like the thermal conductivity. This makes ultrasonics a very effective probe for finite size effects.