Anomalous Attenuation of Transverse Sound in 3He (2008)
Davis, J. P., Pollanen, J., Choi, H., Sauls, J. A., Halperin, W. P., Vorontsov, A. B.
We present the first measurements of the attenuation of transverse sound in superfluid 3He-B. We use fixed path length interferometry combined with the magneto-acoustic Faraday effect to vary the...
Impurity Effects of Aerogel in Superfluid $^{3}$He (2008)
Halperin, W. P., Choi, H., Davis, J. P., Pollanen, J.
The discovery of superfluid $^{3}$He in high porosity silica aerogels, and subsequent experimental and theoretical work, have led to a better general understanding of quasiparticle scattering from...
Superfluid Phase Stability of $^3$He in Axially Anisotropic Aerogel (2008)
Pollanen, J., Davis, J. P., Reddy, B., Shirer, K. R., Choi, H., Halperin, W. P.
Measurements of superfluid $^3$He in 98% aerogel demonstrate the existence of a metastable \emph{A}-like phase and a stable \emph{B}-like phase. It has been suggested that the relative stability of...
Low temperature thermal resistance for a new design of silver sinter heat exchanger (2008)
Pollanen, J., Choi, H., Davis, J. P., Rolfs, B. T., Halperin, W. P.
We have developed a novel procedure for constructing high surface area silver sinter heat exchangers. Our recipe incorporates nylon fibers having a diameter of ~ 50 microns and thin wires of bulk...
High frequency sound in superfluid 3He-B (2008)
Davis, J. P., Choi, H., Pollanen, J., Halperin, W. P.
We present measurements of the absolute phase velocity of transverse and longitudinal sound in superfluid 3He-B at low temperature, extending from the imaginary squashing mode to near pair-breaking....
Davis, J. P., Pollanen, J., Reddy, B., Shirer, K. R., Choi, H., Halperin, W. P.
It has been suggested that anisotropic quasiparticle scattering will stabilize anisotropic phases of superfluid $^3$He contained within highly porous silica aerogel. For example, global anisotropy...
Discovery of an Excited Pair State in Superfluid 3He (2008)
Davis, J. P., Pollanen, J., Choi, H., Sauls, J. A., Halperin, W. P.
Order parameter collective modes are the fingerprint of a condensed phase. The spectroscopy of these modes in superfluid $^3$He and unconventional superconductors can provide key information on the...
Globally Anisotropic High Porosity Silica Aerogels (2007)
Pollanen, J., Shirer, K., Blinstein, S., Davis, J. P., Choi, H., Lippman, T. M., ...
We discuss two methods by which high porosity silica aerogels can be engineered to exhibit global anisotropy. First, anisotropy can be introduced with axial strain. In addition, intrinsic anisotropy...
Strong Coupling Corrections to the Ginzburg-Landau Theory of Superfluid ^{3}He (2007)
Choi, H., Davis, J. P., Pollanen, J., Haard, T. M., Halperin, W. P.
In the Ginzburg-Landau theory of superfluid $^{3}$He, the free energy is expressed as an expansion of invariants of a complex order parameter. Strong coupling effects, which increase with increasing...
Intrinsic Impurity in the High Temperature Superconductor Bi_2Sr_2CaCu_2O$_{8+\delta}$ (2007)
Chen, Bo, Mukhopadhyay, Sutirtha, Halperin, W. P., Guptasarma, Prasenjit, Hinks, D. G.
The {}^{17}O NMR spectra of Bi_2Sr_2CaCu_2O$_{8+\delta}$ (Bi-2212) single crystals were measured in the temperature range from 4 K to 200 K and magnetic fields from 3 to 29 T, reported here...
Two-dimensional Vortices in Superconductors (2007)
Chen, Bo, Halperin, W. P., Guptasarma, Prasenjit, Hinks, D. G., Mitrovic, V. F., Reyes, A. P., ...
Superconductors have two key characteristics. They expel magnetic field and they conduct electrical current with zero resistance. However, both properties are compromised in high magnetic fields...
The Stokes-Einstein Relation in Supercooled Aqueous Solutions of Glycerol (2006)
Chen, Bo, Sigmund, Eric E., Halperin, W. P.
The diffusion of glycerol molecules decreases with decreasing temperature as its viscosity increases in a manner simply described by the Stokes-Einstein(SE) relation. Approaching the glass...
Anisotropy and Penetration Depth of MgB$_{2}$ from ${}^{11}$B NMR (2006)
Chen, Bo, Sengupta, Pratim, Halperin, W. P., Sigmund, E. E., Mitrovic, V. F., Lee, M. H., ...
The ${}^{11}$B NMR spectra in polycrystalline MgB$_2$ were measured for several magnetic fields (1.97 T and 3.15 T) as a function of temperature from 5 K to 40 K. The composite spectra in the...
Collective Modes and f-wave Pairing Interactions in Superfluid 3He (2006)
Davis, J. P., Choi, H., Pollanen, J., Halperin, W. P.
Precision measurements of a collective mode in superfluid 3He B are sensitive to quasiparticle and f wave pairing interactions. Measurements were performed at various pressures using interference of...
Anisotropic Aerogels for Studying Superfluid $^3$He (2006)
Pollanen, J., Blinstein, S., Choi, H., Davis, J. P., Lippman, T. M., Lurio, L. B., ...
It may be possible to stabilize new superfluid phases of $^{3}$He with anisotropic silica aerogels. We discuss two methods that introduce anisotropy in the aerogel on length scales relevant to...
Magnetoresistance of UPt3 (2006)
Lippman, T. M., Davis, J. P., Choi, H., Pollanen, J., Halperin, W. P.
We have performed measurements of the temperature dependence of the magnetoresistance up to 9 T in bulk single crystals of UPt3 with the magnetic field along the b axis, the easy magnetization axis....
Imaginary Squashing Mode Spectroscopy of Helium Three B (2006)
Davis, J. P., Choi, H., Pollanen, J., Halperin, W. P.
We have made precision measurements of the frequency of a collective mode of the superfluid 3He-B order parameter, the J=2- imaginary squashing mode. Measurements were performed at multiple pressures...
Specific Heat of Disordered $^{3}$He (2006)
Choi, H., Davis, J. P., Pollanen, J., Mulders, N., Halperin, W. P.
Porous aerogel is a source of elastic scattering in superfluid 3He and modifies the properties of the superfluid, suppressing the transition temperature and order parameter. The specific heat jumps...
Analysis of Strong-Coupling Parameters for Superfluid 3He (2006)
Choi, H., Davis, J. P., Pollanen, J., Haard, T. M., Halperin, W. P.
Superfluid $^{3}$He experiments show strong deviation from the weak-coupling limit of the Ginzburg-Landau theory, and this discrepancy grows with increasing pressure. Strong-coupling contributions to...
Acoustic Spectroscopy of Superfluid 3He in Aerogel (2006)
Davis, J. P., Choi, H., Pollanen, J., Halperin, W. P.
We have designed an experiment to study the role of global anisotropic quasiparticle scattering on the dirty aerogel superfluid 3He system. We observe significant regions of two stable phases at...
Compressed Silica Aerogels for the Study of Superfluid 3He (2006)
Pollanen, J., Choi, H., Davis, J. P., Blinstein, S., Lippman, T. M., Lurio, L. B., ...
We have performed Small Angle X-ray Scattering (SAXS) on uniaxially strained aerogels and measured the strain-induced structural anisotropy. We use a model to connect our SAXS results to anisotropy...
Surface Specific Heat of $^{3}$He and Andreev Bound States (2006)
Choi, H., Davis, J. P., Pollanen, J., Halperin, W. P.
High resolution measurements of the specific heat of liquid $^{3}$He in the presence of a silver surface have been performed at temperatures near the superfluid transition in the pressure range of 1...
The A-B Transition of Superfluid Helium-3 in Aerogel and the Effect of Anisotropic Scattering (2005)
Vicente, C. L., Choi, H. C., Xia, J. S., Halperin, W. P., Mulders, N., Lee, Y.
We report the results of high frequency acoustic shear impedance measurement on superfluid helium-3 confined in 98% porosity silica aerogel. Using 8.69 MHz continuous wave excitation, we measured the...
Helium-Three in Aerogel (2004)
Liquid 3He confined in silica aerogel provides us with a unique system to study the effects of quenched disorder on the properties of a strongly correlated quantum liquid. The superfluid phases...
Specific Heat of Disordered Superfluid $^{3}$He (2004)
Choi, H., Yawata, K., Haard, T. M., Davis, J. P., Gervais, G., Mulders, N., ...
The specific heat of superfluid $^{3}$He, disordered by a silica aerogel, is found to have a sharp discontinuity marking the thermodynamic transition to superfluidity at a temperature reduced from...
Hole-Burning Diffusion Measurements in High Magnetic Field Gradients (2002)
Sigmund, E. E., Halperin, W. P.
We describe methods for the measurement of translational diffusion in very large static magnetic field gradients by NMR. The techniques use a "hole-burning" sequence that, with the use of fringe...
Antiferromagnetism in the Vortex Cores of YBa$_2$Cu$_3$O$_{7-\delta}$ (2002)
Mitrovi{ć}, V. F., Sigmund, E. E., Halperin, W. P., Reyes, A. P., Kuhns, P., Moulton, W. G.
We report spatially resolved nuclear magnetic resonance measurements on a high temperature superconductor that indicate the presence of correlated antiferromagnetic fluctuations in the vortex core....
Phase Diagram of the Superfluid Phases of 3He in 98% Aerogel (2002)
Gervais, G., Yawata, K., Mulders, N., Halperin, W. P.
The phase diagram of the superfluid phases of $^{3}$He in 98% aerogel was determined in the range of pressure from 15 to 33 bars and for fields up to 3 kG using high-frequency sound. The superfluid...
Nucleation and Interfacial Coupling between Pure and Dirty Superfluid Phases of 3He (2001)
Gervais, G., Yawata, K., Mulders, N., Halperin, W. P.
The nucleation of the first order phase transition of superfluid 3He-B from superfluid 3He-A is quite remarkable since it requires a seed of the order of a micron. We have studied this nucleation for...
Mitrovi{ć}, V. F., Sigmund, E. E., Eschrig, M., Bachman, H. N., Halperin, W. P., Reyes, A. P., ...
One of the puzzling aspects of high temperature superconductors is the prevalence of magnetism in the normal state and the persistence of superconductivity in very high magnetic fields. Generally,...
The Pseudogap in YBa$_2$Cu$_3$O$_{7-\delta}$ from NMR in High Magnetic Fields (2001)
Mitrovi{ć}, V. F., Bachman, H. N., Halperin, W. P., Reyes, A. P., Kuhns, P., Moulton, W. G.
We report $^{17}$O(2,3) and $^{63}$Cu(2) spin-lattice relaxation rates and the $^{17}$O(2,3) spin-spin relaxation rate in different magnetic fields in YBa$_2$Cu$_3$O$_7$ near $T_c$. Together these...
Magneto-acoustic rotation of transverse waves in 3He-B (1999)
Sauls, J. A., Lee, Y., Haard, T. M., Halperin, W. P.
In superfluid 3He-B the off-resonant coupling of the J=2-, M=+/- 1 order parameter collective modes to transverse current excitations stabilizes propagating transverse waves with low damping for...
Discovery of the Acoustic Faraday Effect in Superfluid 3He-B (1999)
Lee, Y., Haard, T. M., Halperin, W. P., Sauls, J. A.
We report the discovery of the acoustic Faraday effect in superfluid 3He-B. The observation of this effect provides the first direct evidence for propagating transverse acoustic waves in liquid 3He,...
Superconducting Fluctuation Effects on the Spin-Lattice Relaxation Rate in YBa_2Cu_3O_{6.95} (1999)
Mitrovi{ć}, V. F., Bachman, H. N., Halperin, W. P., Eschrig, M., Sauls, J. A., Reyes, A. P., ...
We report 63Cu(2) spin-lattice relaxation rate measurements of YBa_2Cu_3O_{6.95} in magnetic fields from 2.1 T to 27.3 T obtained from 17O(2,3) nuclear magnetic resonance spin-spin relaxation. For T...
Superconducting Fluctuation Effects on the Electron Spin Susceptibility in YBa_2Cu_3O_{6.95} (1999)
Bachman, H. N., Mitrovi{ć}, V. F., Reyes, A. P., Halperin, W. P., Eschrig, M., Sauls, J. A., ...
The electronic spin susceptibility of YBa_2Cu_3O_{6.95} has been measured with high precision up to 24 Tesla with 17O nuclear magnetic resonance. Its temperature dependence can be accounted for by...
Mitrovi{ć}, V. F., Bachman, H. N., Halperin, W. P., Eschrig, M., Sauls, J. A.
In a recent Letter of Gorny et al. it was reported that the spin-lattice relaxation rate in YBCO_{7-d} is magnetic field independent. These authors point out that their results are inconsistent with...
Suppression of Superconductivity in UPt_3 Single Crystals (1998)
Kycia, J. B., Hong, J. I., Graf, M. J., Sauls, J. A., Seidman, D. N., Halperin, W. P.
High quality single crystals of UPt_3 have been prepared by vertical float-zone refining in ultra-high vacuum. We find that the superconducting transition temperature can be varied systematically by...
On the use of CMN thermometry in specific heat measurements below 10 mK (1979)
It is pointed out that small deviations of the cerium magnesium nitrate (CMN) temperature scale from the thermodynamic one, may give rise to significant errors in interpretation of specific heat...
On the use of CMN thermometry in specific heat measurements below 10 mK (1979)
It is pointed out that small deviations of the cerium magnesium nitrate (CMN) temperature scale from the thermodynamic one, may give rise to significant errors in interpretation of specific heat...
On the use of CMN thermometry in specific heat measurements below 10 mK (1979)
It is pointed out that small deviations of the cerium magnesium nitrate (CMN) temperature scale from the thermodynamic one, may give rise to significant errors in interpretation of specific heat...