Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session X33: Quantum Fluids and Solids I 
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Sponsoring Units: DCMP Room: C143/149 
Thursday, March 24, 2011 2:30PM  2:42PM 
X33.00001: Characterization of MEMS Devices for the Study of Superfluid Helium Films Miguel Gonzalez, Byoung Hee Moon, Pradeep Bhupathi, Pan Zheng, George Ling, Erik Garcell, Ho Bun Chan, Yoonseok Lee Measurements on the mechanical attributes of MEMS resonators were performed at room and low temperatures. Specially devised resonators which can be actuated for shear motion were designed and fabricated using a stateof theart multiuser MEMS process. The devices consist of a pair of parallel plates with a welldefined gap whose size can be controlled with high accuracy down to the submicron range. A full study of resonance properties at various pressures was performed at room temperature. Details of design, fabrication, and operation will be presented along with results from a preliminary study of a resonator immersed in liquid $^{4}$He. The devices show potential for use in low temperature experiments and to investigate novel phenomena in quantum fluids at the micro/nano scale such as superfluid $^{3}$He films. [Preview Abstract] 
Thursday, March 24, 2011 2:42PM  2:54PM 
X33.00002: Interplay of Aerogel Anisotropy and Textures in Superfluid $^3$He Jia Li, Johannes Pollanen, Charles Collett, William J. Gannon, William P. Halperin We have performed pulsed NMR on $^3$HeB in $98.1\%$ porosity aerogel with different anisotropy. The aerogel anisotropy was characterized with an optical, crosspolarization technique [1]. In the isotropic aerogel sample at P = 26 bar and $T<1.2mK$, we find a single peak with a positive frequency shift relative to the Lamor frequency indicating an ntexture that is predominately perpendicular to the field. Upon warming, we find a crossover at $T\approx1.2mK$ from $n\perp \mathbf{H}$ to a texture where n is predominately parallel to the field. Near the crossover the NMR intensity is distributed among two components indicating an inhomogeneous texture. We have also studied an anisotropic aerogel which was compressed along its cylinder axis by $22.5\%$. At the same pressure, we find a homogeneous texture for all $T$ and a similar textural crossover from $n\perp \mathbf{H}$ to $n \parallel \mathbf{H}$, but for this sample the textural crossover happens near $T_{caerogel}$. We have introduced a model to account for the interplay of aerogel anisotropy and ntextures. Currently we are studying the tip angle dependence of NMR frequency shifts in these aerogels. This work was supported by the National Science Foundation, DMR0703656.\\[0pt] [1] J. Pollanen et al. \emph{J. of NonCrystalline Solids} \textbf{354}, 4668 (2008). [Preview Abstract] 
Thursday, March 24, 2011 2:54PM  3:06PM 
X33.00003: EqualSpin Pairing Superfluid State of $^3$He in Radially Compressed Aerogel J. Pollanen, J. Li, C. Collett, W.J. Gannon, W. P. Halperin Anisotropic quasiparticle scattering has been predicted to stabilize anisotropic superfluid states of $^3$He [1,2]. We have performed pulsed nuclear magnetic resonance (NMR) experiments on $^3$He in a homogeneously anisotropic $97.5\%$ porosity aerogel. From the NMR frequency shifts on warming at P = 26 bar we find a single superfluid state exists between $0.7 mK$ and $T_{caero} = 1.67mK$. Susceptibility measurements indicate this phase is an equalspin pairing (ESP) state. The anisotropy of our cylindrical aerogel sample was induced during the growth and drying stages in the form of $14.3\%$ radial compression. The sample was characterized with an optical, crosspolarization technique [3] to confirm the presence of a homogeneous optical axis aligned with the cylinder axis. Similar experiments and characterization have been performed on a homogeneously isotropic $98.1\%$ aerogel and, in this case, we find the nonESP aerogel Bphase is the stable state. We are currently studying the tip angle dependence of the NMR frequency shift to identify which of the ESP states we have observed and to explore the full PT phase diagram of superfluid $^3$He in these aerogels. This work was supported by the National Science Foundation, DMR0703656. [1] C.L. Vicente, et al., PRB 72, 094519 (2005). [2] K. Aoyama and R. Ikeda, PRB 73, 060504(R) (2006). [3] J. Pollanen et al., JNCS 354, 4668 (2008). [Preview Abstract] 
Thursday, March 24, 2011 3:06PM  3:18PM 
X33.00004: Moderate Magnetic Field Transverse Acoustics in Superfluid $^3$HeB C. Collett, S. Sasaki, J.P. Davis, J. Pollanen, W.J. Gannon, J. Li, W.P. Halperin We present the results of transverse acoustics studies in superfluid $^3$HeB at fields up to 0.1 T. Using acoustic cavity interferometry, we observe the acoustic Faraday effect\footnote{G.F. Moores and J.A. Sauls, J. Low Temp. Phys. {\bf 91}, 13 (1993).}$^,$\footnote{Y. Lee {\it et al.}, Nature {\bf 400}, 431 (1999).} for a transverse sound wave propagating along the magnetic field, and we measure Faraday rotations of the polarization of the sound up to 990$^\circ$, significantly more extensive than has been previously reported. We use these results to extend previous calculations of the Land\'e \textit{g} factor. We also find the field dependence of cavity interference oscillations resulting from coupling to the imaginary squashing mode (ISQ), a collective mode of the order parameter with total angular momentum $J=2$. Measurements in large magnetic fields were performed at frequencies up to the pair breaking threshold, where there has been a recent report\footnote{J.P. Davis {\it et al.}, Nature Physics {\bf 4}, 571 (2008).} of a new collective mode with $J=4$. The discovery of Faraday rotations coming from this new mode is reported, along with their intersection with rotations from the ISQ. Support for this work from the NSF, grant DMR0703656, is gratefully acknowledged. [Preview Abstract] 
Thursday, March 24, 2011 3:18PM  3:30PM 
X33.00005: L\'evy Flights and Anomalous Diffusion in Liquid $^3$HeAerogel James Sauls The transport of heat by liquid $^3$He impregated into silica aerogel is limited at low temperatures by elastic scattering of quasiparticles by the aerogel. The gossamer structure of silica aerogel is a realization of a random fractal  a solid with no longrange order, but powerlaw scaling of the density correlation function. Complementary to fractal scaling of the particleparticle correlation function is the appearance of a power law distribution of {\sl free flight paths}. The open structure shown in the DLCA simulations of lowdensity aerogel leads to a distribution of exceedingly long flight paths governed by a L\'evy distribution. I describe a theory for anomalous diffusion of quasiparticles in which the L\'evy distribution of long free paths is interrupted by inelastic collisions between quasiparticles. These rare events lead to finite temperature corrections to the thermal diffusion coefficient of the form, $\kappa/T = K_{0}  K_{1}\,(T/T^{\star})^{\beta}$, where $T^{\star}$ is the temperature at which the elastic and inelastic mean free paths are equal and $\beta$ is related to the fractal dimension of the L\'evy distribution. [Preview Abstract] 
Thursday, March 24, 2011 3:30PM  3:42PM 
X33.00006: Signatures of Crystalline Phases and Domain Walls in Superfluid $^3$He Thin Films Anton Vorontsov, James Sauls Thin films of superfluid $^3$He may spontaneously break translation symmetry in the plane of the film.\footnote{Phys. Rev. Lett. 98,045301 (2007).} Near a critical film thickness, $D_{c_1}\approx 13\,\xi_0$, a onedimensional ``stripe phase'' develops as a periodic array of domain walls separating degenerate, but inequivalent Bphases, $(\Delta_{},\Delta_{},+\Delta_{\perp})$ and $(\Delta_{},\Delta_{},\Delta_{\perp})$. These defects have a unique spectrum of topological excitations bound to the domain wall. We present results for the order parameter and Fermionic spectrum, and their observable signatures, for a single domain wall and for the stripe phase. The combination of particlehole asymmetry and broken translational symmetry of the order parameter leads to a weak modulation of the density, $\delta n \sim \ln\left(E_f/k_B T_c\right)\left(k_B T_c/E_f\right)^2\,\bar{n}$, where $\bar{n}$ is the mean particle density. This leads to a modulation of the van der Walls attraction, and thus a small, static modulation of the film thickness. We report theoretical results for the density modulation, film thickness profile and optical reflectivity for the crystalline phases of superfluid $^3$He. [Preview Abstract] 
Thursday, March 24, 2011 3:42PM  3:54PM 
X33.00007: Visualization of counterflow dynamics using frozen nanoparticles Enrico Fonda, Matthew S. Paoletti, Katepalli R. Sreenivasan, Daniel P. Lathrop We study the dynamics of quantized vortices and quantum turbulence utilizing a particle tracking visualization technique. This is accomplished by using submicron and micronsized hydrogen or atmospheric ice particles injected into He$^{4}$ flows that get trapped on the vortices. This technique has been used to observe and characterize reconnection of quantized vortices and thermal counterflow. We present the latest results using nanosized ice particles. These submicron particles are superior to larger particles in a number of ways. In particular, being less affected by Stokes drag, they stay trapped on faster moving vortices and remain trapped closer to the lambda transition. Using these particles, we have made additional observations of counterflows at higher heat fluxes to shed light on the particlevortex interaction mechanism. The technique has also been extended for visualization for fluid dynamics experiments using liquid nitrogen. [Preview Abstract] 
Thursday, March 24, 2011 3:54PM  4:06PM 
X33.00008: Numerical Real Space Renormalization of a 2D Random Boson Model Shankar Iyer, Gil Refael Interest in the random boson problem originated in experiments on Helium adsorbed in Vycor, but the problem arises in many contexts, including Josephson junction arrays and disordered cold atom systems. Recently, Altman, Kafri, Polkovnikov, and Refael have studied a rotor model description of interacting bosons subjected to quenched disorder in one dimension. Using a real space renormalization approach, they have identified a random fixed point that marks the transition between superfluid and Mottglass phases. Here, we describe work that numerically extends their approach to the random boson problem in two dimensions. We first test the validity of the real space renormalization by comparison to exact diagonalization of small systems. Then, we move to larger systems and explore what the renormalization scheme can tell us about the nature of the insulating and superfluid phases. [Preview Abstract] 
Thursday, March 24, 2011 4:06PM  4:18PM 
X33.00009: Third Sound in Superfluid $^{4}$He Films Adsorbed on Packed Multiwall Carbon Nanotubes Emin Menachekanian, Gary A. Williams An investigation of thirdsound propagation is carried out with thin $^{4}$He films adsorbed on multiwall carbon nanotubes. At an average diameter of 12 nm and a length of several microns, the powder of nanotubes is lightly packed into a cylindrical resonator, with a resistor bolometer at the cylinder end to detect the temperature oscillations accompanying the waves. The lowest standingwave mode in the cavity is excited by mechanical vibrations, with FFT analysis allowing measurement of the sound speed as well as the dissipation. The KosterlitzThouless onset transition is observed with increasing film thickness for temperatures between 1.3 and 1.7 K. At higher thicknesses capillary condensation becomes important, probably at connection points where the nanotubes touch. Layering effects in the thirdsound velocity, associated with the relatively strong van der Waals coupling between helium and carbon, are not observed, and measurements below 1 K may be necessary to see this. There is also no indication of any effect of superfluidity attributable to the adsorption of helium on the inner surfaces of the nanotubes. [Preview Abstract] 

X33.00010: ABSTRACT WITHDRAWN 
Thursday, March 24, 2011 4:30PM  4:42PM 
X33.00011: VortexLoop Thermodynamics of Superfluid $^4$He Under Pressure Andrew Forrester, Gary A. Williams The thermodynamic quantities of pressurized superfluid $^4$He near the $\lambda$transition are calculated using a vortexloop renormalization method. The superfluid density, specific heat, vortex core size, and vortex core energy are determined as functions of pressure and temperature, and compared with experiments. The theory predicts exponents describing the critical behavior of the superfluid density and specific heat that are in agreement with recent highprecision theoretical simulations. The vortex core size is found to increase with pressure, while the core energy decreases, the behavior found experimentally for both parameters. The specific heat, though strongly dependent on both of these parameters, is found to scale with pressure in agreement with experimental measurements. [Preview Abstract] 
Thursday, March 24, 2011 4:42PM  4:54PM 
X33.00012: Topological and geometrical interactions between quantum vortices near zero temperature Ran Cheng, Xiao Li, Qian Niu With new velocitydependent term discovered, various types of interactions between quantum vortices in 2d superfluid Helium and BEC near zero temperature are unified via Berry Phase theory. Originated from the finite compressibility of the fluid, the topological statistical gauge field of an vortex breaks down to geometrical gauge field mediating local interactions. This new interaction modifies the cyclotron motion of a pair of identical vortices, and changes the pattern of orbits of a pair of vortexantivortex. Damping effect due to finite temperature is treated phenomenologically, which does not invalidate our essential conclusions. [Preview Abstract] 
Thursday, March 24, 2011 4:54PM  5:06PM 
X33.00013: Semiclassical dynamics of vortices in superfluid helium thin films Xiao Li, Ran Cheng, Qian Niu Based on the Berry phase theory, we consider the case of two vortices in Bosonic superfluids and try to extract the interaction between them. Under the adiabatic approximation, we use semiclassical Lagrangian formalism to describe the system and found that in addition to the universal background ``magnetic field'' which results in the Magnus force, there exists a new interaction mediated by the density profile of the background fluid due to its finite compressibility. Finally, numerical solutions from the nonlinear Schrodinger equation were employed to gain better insight into this problem. [Preview Abstract] 
Thursday, March 24, 2011 5:06PM  5:18PM 
X33.00014: Theory of the Boseglass states in Brdoped NickelTetrakis Thiourea (DTN) Rong Yu, Stephan Haas, Tommaso Roscilde We present extensive Quantum Monte Carlo calculations on bonddisordered coupled spin chains with strong singleion anisotropy, modeling the behavior of Brdoped NickelTetrakis Thiourea (DTN). Our model quantitatively describes the phase diagram of the experimental compound  in particular the lowtemperature magnetization curve and the critical temperature for magnetic BoseEinstein condensation as a function of the field. Hence it provides fundamental insight into the nature of the Boseglass phases appearing at low temperature close to the two critical fields for condensation. Brdoped bonds act as nucleation centers of magnetic quasiparticles in the lowfield Bose glass, while at high fields the Brdoped bonds represent the localization centers of magnetic quasiholes. The quantitative understanding of Brdoped DTN opens the way to a detailed investigation of Boseglass physics in quantum magnets. [Preview Abstract] 
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