Ultrasonic propagation in /sup 3/He--/sup 4/He mixtures near the tricritical point

Journal Article · Wed Jun 01 00:00:00 EDT 1977 · J. Low Temp. Phys.; (United States)

DOI:https://doi.org/10.1007/BF00655706· OSTI ID:7319306

Roe, D B; Ruppeiner, G; Meyer, H

We present measurements of the singular sound attenuation ..cap alpha../sub sing/ in liquid mixtures of /sup 3/He and /sup 4/He near the superfluid transition and at temperatures above the phase separation curve. The mole fraction X of /sup 3/He ranged from 0.55 to 0.73 and the frequency ..omega../2..pi.. varied between 1 and 45 MHz. The temperature range was 0.75--1.4 K, with the greatest emphasis on the tricritical region near X/sub t/=0.67 and T/sub t/=0.87 K. From the change in slope dU/dT of the sound velocity U, we present a new determination of the phase separation curve, which is compared with previous measurements. The sound attenuation peak along the superfluid transition becomes broader in temperature as T/sub lambda/is decreased. In addition, there is also an increase in sound attenuation as the phase separation temperature T/sub sigma/is approached. For X0.55 the observed attenuation can be analyzed solely in terms of the diffusive relaxation mechanism. The mass diffusion parameter D is then determined from the data. At X=0.55, D diverges as T/sub lambda/is approached, which is consistent with theoretical expectations and experimental results. Near T/sub t/, there is a crossover to a tricritical regime, and it is found that approximately Dproportional (T-T/sub t/)/sup Z/ with Z=0.32 +- 0.1. Mode coupling predictions are that Z=1/2 while recent renormalization group calculations give Z=1/3.

• Research Organization: Department of Physics, Duke University, Durham, North Carolina
• OSTI ID: 7319306
• Journal Information: J. Low Temp. Phys.; (United States), Vol. 27:5
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
HELIUM 3
ULTRASONIC WAVES
HELIUM 4
ABSORPTION
MHZ RANGE 01-100
PHASE TRANSFORMATIONS
QUANTITY RATIO
SUPERFLUIDITY
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FREQUENCY RANGE
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
MHZ RANGE
NUCLEI
SOUND WAVES
STABLE ISOTOPES
640450* - Fluid Physics- Superfluidity