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Title: Entropy of solid {sup 4}He: The possible role of a dislocation-induced glass

Abstract

Solid {sup 4}He is viewed as a nearly perfect Debye solid. Yet recent calorimetry indicates that its low-temperature specific heat has both cubic and linear contributions. These features appear in the same temperature range (T{approx}200 mK) where measurements of the torsional oscillator period suggest a supersolid transition. We analyze the specific heat to compare the measured with the estimated entropy for a proposed supersolid transition with 1% superfluid fraction. We find that the experimental entropy is substantially less than the calculated entropy. We suggest that the low-temperature linear term in the specific heat is due to a glassy state that develops at low temperatures and is caused by a distribution of tunneling systems in the crystal. It is proposed that small scale dislocation loops produce those tunneling systems. We argue that the reported mass decoupling is consistent with an increase in the oscillator frequency, as expected for a glasslike transition.

Authors:
; ;  [1];  [2]
  1. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
  2. Department of Physics, Washington University, St. Louis, Missouri 63160 (United States)
Publication Date:
OSTI Identifier:
20976719
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 9; Other Information: DOI: 10.1103/PhysRevB.75.094201; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CALORIMETRY; COMPARATIVE EVALUATIONS; CRYSTALS; DECOUPLING; DISLOCATIONS; ENTROPY; GLASS; HELIUM; HELIUM 4; OSCILLATORS; SOLIDS; SPECIFIC HEAT; TEMPERATURE RANGE 0065-0273 K; TUNNEL EFFECT

Citation Formats

Balatsky, A. V., Graf, M. J., Trugman, S. A., and Nussinov, Z. Entropy of solid {sup 4}He: The possible role of a dislocation-induced glass. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.094201.
Balatsky, A. V., Graf, M. J., Trugman, S. A., & Nussinov, Z. Entropy of solid {sup 4}He: The possible role of a dislocation-induced glass. United States. doi:10.1103/PHYSREVB.75.094201.
Balatsky, A. V., Graf, M. J., Trugman, S. A., and Nussinov, Z. Thu . "Entropy of solid {sup 4}He: The possible role of a dislocation-induced glass". United States. doi:10.1103/PHYSREVB.75.094201.
@article{osti_20976719,
title = {Entropy of solid {sup 4}He: The possible role of a dislocation-induced glass},
author = {Balatsky, A. V. and Graf, M. J. and Trugman, S. A. and Nussinov, Z.},
abstractNote = {Solid {sup 4}He is viewed as a nearly perfect Debye solid. Yet recent calorimetry indicates that its low-temperature specific heat has both cubic and linear contributions. These features appear in the same temperature range (T{approx}200 mK) where measurements of the torsional oscillator period suggest a supersolid transition. We analyze the specific heat to compare the measured with the estimated entropy for a proposed supersolid transition with 1% superfluid fraction. We find that the experimental entropy is substantially less than the calculated entropy. We suggest that the low-temperature linear term in the specific heat is due to a glassy state that develops at low temperatures and is caused by a distribution of tunneling systems in the crystal. It is proposed that small scale dislocation loops produce those tunneling systems. We argue that the reported mass decoupling is consistent with an increase in the oscillator frequency, as expected for a glasslike transition.},
doi = {10.1103/PHYSREVB.75.094201},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 9,
volume = 75,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}
  • The density of liquid /sup 4/He has been measured along the melting curve in the temperature range 0.1--0.82 K by observing the change with temperature of the resonant frequency of a superconducting microwave cavity immersed in the liquid. Relative changes in density as small as 4 x 10/sup -9/ could be resolved. From the results the entropy of solid /sup 4/He was obtained by using the Clausius-Clapeyron equation in conjunction with values for the isobaric-thermal-expansion coefficient and entropy of the liquid calculated from other data. No evidence for an anomalous linear temperature term in the entropy of the solid wasmore » found. The data are shown to be in good agreement with published measurements of the Debye temperature of the solid by Gardner, Hoffer, and Phillips. (AIP)« less
  • The properties of pure /sup 6/He and /sup 6/He--/sup 4/He and /sup 6/He--/sup 3/He mixtures are studied within the context of the quantum theorem of corresponding states. For pure /sup 6/He, it is found that there is a small, but definite, region where it is expected to be superfluid. For the /sup 6/He--/sup 4/He mixture, it is found that there is a ''lambda-eutectic'' temperature, approximately 1.2 K, below which it is expected that both /sup 6/He and /sup 4/He will be part of the superfluid at all concentrations. Experiments to observe /sup 6/He superfluidity are discussed, and it is concludedmore » that such experiments are feasible, although they may be quite difficult to carry out. Experiments are discussed to use a /sup 6/He generator (should it be possible to construct it) as a probe to study various properties of liquid and solid helium.« less
  • Using a capacitive pressure gauge, the pressure of a constant-volume {sup 4}He-sample was measured in the temperature range 1.5-120 mK, at pressures of 25.3 bar (on the melting curve) and 26.0 bar. A gradual pressure change occurring as a consequence of the ideal-gas behavior of vacancies, or a pressure anomaly corresponding to a Bose-Einstein condensation of the vacancies, was not observed. Within the sensitivity of the pressure gauge (2 Pa), this result sets upper limits to the density of zero-point vacancies.