• Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Journal of the Acoustical Society of America

SECTION LISTING

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Nov 1989

Volume 86, Issue S1, pp. S1-S125

Return to All Sections
back to top
RSS Feeds
back to top Session EE. Physical Acoustics V: Mechanical Wave Propagation in Condensed Matter Physics
Invited Papers
FREE

Ultrasonic absorption in the magnetic superconducting system Er1−x\HoxRh4B4 (A)

Keun J. Sun

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S73-S73 (1989); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
Ultrasonic attenuation measurements as a function of temperature at constant magnetic fields and as a function of magnetic field at constant temperatures in Er1−xHoxRh4B4 show interesting behavior at low temperatures. The enhanced attenuation observed in the superconducting state and the sharp change in attenuation at magnetic phase transition for the superconductors in this system are attributed to spin‐phonon interaction. The peculiar dependence of attenuation on orientation of magnetic field with respect to sound wave propagation direction evidences indirectly the coexistence of magnetic order and superconductivity. A two‐level model of phonon‐phonon interaction is proposed to elucidate the occurrence of relaxation type attenuation maxima observed in the temperature‐dependent attenuation curves of all the samples. Furthermore, the attenuation behavior at low temperatures in high magnetic fields may also manifest the occurrence of a new magnetoelastic coupling effect.
FREE

Ultrasonic attenuation measurements on the heavy fermion superconductor UPt3 (A)

B. K. Sarma, M. Levy, A. Schenstrom, Y.‐J. Qian, M.‐F. Xu, S. Adenwalla, J. B. Ketterson, Z. Zhao, and D. Hinks

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S73-S73 (1989); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
The superconducting pairing mechanism in the heavy fermion superconductor UPt3 is unconventional, as evidenced from any of its low‐temperature properties. Recent ultrasonic absorption, heat capacity, and magnetization measurements show a multiplicity of phases in the H‐T plane, suggesting an exotic order parameter. The experimental results will be reviewed. [Work supported by ONR and NSF.]
FREE

Ultrasonic studies of collective modes in superfluid 3He (A)

John B. Ketterson

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S73-S73 (1989); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
Liquid 3He undergoes a transition at a temperature of 2×10−3 K into a superfluid state. The state is related to the paired‐electron state of the BCS theory of superconductivity but differs in that the 3He atoms are paired in an L = 1 (p wave), S = 1 (triplet) state [rather than the L = 0 (s wave), S = 0 (singlet) state of conventional superconductivity]. Various excited states of the superfluid exist, which are referred to as excitonic or collective modes, and, loosely, they correspond to various values of the total angular momentum J = L + S. Some of these modes couple strongly with ultrasound. A brief review is presented of these collective modes and of the ultrasonic experiments performed to date, which probe their behavior as a function of temperature and magnetic field.
FREE

Wave localization in anisotropic random media (A)

Ping Sheng

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S74-S74 (1989); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
As a phenomenon generic to waves in random media, localization has many general features common to both quantum particles, e.g., electrons, and classical waves, e.g., electromagnetic and elastic waves. One such aspect is that all waves localize in two‐ or one‐dimensional systems with an arbitrary amount of randomness, and that in three dimensions a wave localizes only in certain energy regimes that are separated from the delocalized regimes by so‐called mobility edges. In this paper, the results of recent work on the anisotropic dimensional crossover behavior for wave localization are described. Starting from a randomly layered medium, some scattering centers were introduced, i.e., inhomogeneities, into each of the layers in a controlled manner. These inhomogeneities cause the wave to scatter out of the layering direction. When the strength and the density of the scattering inhomogeneities become equal to the randomness encountered in propagating from layer to layer, then the system becomes an isotropic, 3‐D random medium. Therefore, in increasing the scattering strength and density of the scatterers there is essentially a “cross over” from one‐dimensional randomness, where all waves are localized, to isotropic three‐dimensional randomness, where there can be mobility edges. What is found is that there is a critical anisotropy below which the system behaves as 1 D and above which the system behaves as 3 D. In other words, the transition is achieved in a discontinuous manner. The talk will emphasize the underlying physics of the localization and its anisotropic critical transition.
FREE

Surface acoustic waves on nonlinear substrates (A)

Alexei A. Maradudin

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S74-S74 (1989); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
The nonlinearity of the substrate on which a surface acoustic wave propagates causes acoustical rectification of the surface wave, harmonic generation and nonlinear mixing of surface waves, and the acoustoelastic effect. It gives rise to weakly nonlinear surface acoustic waves, and to associated surface acoustic solitary waves. The spatial dispersion required for the existence of the latter is introduced by coating the substrate by a thin film with different material properties. Explicit conditions for the formation of envelope solitons are presented, as well as for self‐focusing of the surface acoustic waves. The nonlinearity can also cause Love waves to become leaky with an amplitude‐dependent damping constant. Finally, a periodic corrugation of the surface of a nonlinear elastic substrate is used to introduce spatial dispersion into the system. An amplitude dependence of the stop bands for the propagation of weakly nonlinear surface acoustic waves across the resulting periodic structure, and an amplitude‐dependent attenuation in the case of sagittal polarization, are found. [Work supported by NSF Grant No. DMR 88‐15866.]
FREE

Relating macroscopic deformation to site symmetry changes around the Cr+++ in shocked ruby crystals (A)

Y. M. Gupta

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S74-S74 (1989); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
An important but very difficult problem in shock wave research is to understand and interpret time‐resolved, continuum measurements in condensed materials in terms of changes at the atomic/molecular level. As a start toward this challenging problem, experimental and theoretical studies on understanding the luminescence R‐line spectra in shocked ruby crystals have been carried out. Time‐resolved experiments have been performed to obtain wavelength shifts under macroscopically, well‐defined compression and tension loading, and for shock wave propagation along the crystal c and a axes. Below the Hugoniot elastic limit (≈13 GPa), the observed R‐line spectra are strongly anisotropic and show nonlinear shifts with density for both compression and tension. For the theoretical analysis, the deformation potential is written in terms of symmetry adapted basis according to the irreducible representation of local octahedral group. Using the symmetry of the macroscopic strain, the perturbative effects of the deformation potential are evaluated for the 2E state that gives rise to the R lines. Results not only from the shock experiments but also from hydrostatic and uniaxial stress experiments can be analyzed consistently using these analytic developments. A summary of the experimental and analytical work will be presented. [This work was carried out in collaboration with S. M. Sharma, X. A. Shen, P. D. Horn, and J. A. Butt and supported by ONR Contract N00014‐86‐0307.]
FREE

Ballistic phonon mediated detection of elementary particles in silicon (A)

B. Neuhauser, B. Cabrera, A. T. Lee, B. A. Young, C. J. Martoff, and J. P. McVittie

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S74-S75 (1989); (2 pages)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
When an incident particle collides with an electron or nucleus in a silicon crystal, 70% of the recoil energy is converted into a burst of low‐energy phonons. These phonons propagate ballistically for distances of several centimeters if the crystal has very few defects or impurities and if it is cooled to a temperature well below 1 K. Direct sensing of the phonons is the basis for a new type of elementary particle detector, called a silicon crystal acoustic detector (SiCAD), which will be used in neutrino experiments and in the search for other weakly interacting particles. The first generation of ultrasensitive phonon detectors consists of a thin film strip of a superconducting material, which is current biased just below the critical temperature. Incident phonons drive a segment of the film normal and thereby produce a voltage pulse. These devices have sufficient sensitivity and resolution to detect energy depositions of several keV in standard 3‐in. silicon wafers. Research currently is in progress on the next generation of phonon detectors that will make use of superconducting tunnel junctions. [Work supported by DOE, NSF, and Research Corporation.]
Contributed Paper
FREE

Using a SQUID acoustomagnetic spectrometer to characterize continuous wave acoustic response observations (A)

Ronald K. Sundfors and Mark R. Holland

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S75-S75 (1989); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
A SQUID acoustomagnetic spectrometer is used to detect changes of magnetization of tantalum metal produced by a continuous wave composite resonator in an external magnetic field. Acoustic power variations produce temperature variations in the spectrum and thus cause changes in the Curie susceptibility of the paramagnetic impurities present in the sample. Swept frequency acoustic spectra of single‐crystal tantalum standing wave resonances at the normal mode frequencies (mechanical resonances) are studied at 4.2 K. Depending on the rate of frequency sweep through a mechanical resonance, the applied acoustic power, and the magnetic field, the observed structure at the mechanical resonance frequencies can be both above and below the baseline. The low‐frequency side of each structure has a Lorentz line shape and the high‐frequency side has an exponential decay that is explained by heat exchange between sample and surroundings. This interpretation allows these structures to be used in general in continuous wave velocity of sound and ultrasonic attenuation studies while making use of the high sensitivity of the SQUID acoustomagnetic spectrometer.
Return to All Sections
Close

Home Publications Meetings Contact ASA Site Map Back to Top

Copyright © Acoustical Society of America

close