Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session A45: Helium 3 and Electron Hydrodynamics 
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Sponsoring Units: DCMP Chair: Johannes Pollanen, Michigan State Univ Room: LACC 505 
Monday, March 5, 2018 8:00AM  8:12AM 
A45.00001: Pair breaking at the surface of the unconventional superfluid Petri Heikkinen, Andrew Casey, Lev Levitin, Xavier Rojas, John Saunders, Anton Vorontsov, Nik Zhelev, Jeevak Parpia In unconventional pwave superfluid ^{3}He, Cooper pairs are subject to anisotropic pair breaking in the vicinity of surfaces and interfaces. This effect dominates when the superfluid is confined in a cavity of height comparable to the coherence length. The surface pairbreaking depends on the boundary condition for surface scattering of quasiparticles. We study superfluid ^{3}He confined in a single nanofabricated 200 nm high cavity, using SQUIDNMR as a probe of superfluid order parameter, and pressure as a tuning parameter. The surface scattering is also tuned in situ, by adjustment of the surface boundary layer. We make an accurate determination of the suppression of the superfluid transition temperature, T_{c}. We also measure the gap suppression for different boundary conditions. With a solid ^{4}He surface layer we find close to diffuse scattering, while by coating the surface with a superfluid ^{4}He film we find close to perfect specular scattering, with the almost complete elimination of T_{c} and gap suppression. With a solid ^{3}He layer on the surface, the observed T_{c} suppression is significantly stronger than that predicted by quasiclassical theory with diffuse scattering boundary conditions. 
Monday, March 5, 2018 8:12AM  8:24AM 
A45.00002: Magneticallyactive Boundaries in Topological Superfluid 3HeB Anton Vorontsov We calculate properties of the BW phase of superfluid Helium3 near magneticallyactive boundaries using quasiclassical theory. The quasiparticles acquire spindependent phase shift when scattering off such surfaces. This local breaking of the timereversal symmetry by the boundary is sufficient to remove the topological protection of the surface zeroenergy Majorana modes. We investigate how magnetic scattering affects the order parameter structure, surface density of states and helical surface spin currents. In HeB the spin and orbital degrees of freedom are connected by the broken relative spinorbit rotational symmetry, and magnetic boundaries can provide a more flexible control of the surface bound states. In particular, we show that such boundaries strongly affect superfluid phases in confined geometry, such as slabs with thickness of several coherence length. 
Monday, March 5, 2018 8:24AM  8:36AM 
A45.00003: Thermal Conductivity of 3He confined in a 1.1 micron sized channel. Jeevak Parpia, Anna Eyal, Nikolay Zhelev, Dmytro Lotnyk, Michael Terilli, Abhilash Sebastain, Eric Smith We describe the results of experiments on the thermal conductivity of 3He confined to a nanofabricated channel of ~1.1 um height, fabricated in silicon that is anodically bonded to glass. The channel separates a 3He filled chamber of small volume containing a fork thermometer/heater from a separate chamber with a silver heat exchanger filled with 3He, which contains an identical fork thermometer. In the normal state of 3He at low pressure, an anticipated crossover from Fermiliquid (inelastic scattering length varying as T^{2}) to mean freepathlimited behavior (scattering length dominated by boundary scattering) is observed. In the superfluid, the presence of twofluid flow near T_{c} is investigated and the supercooling and nucleation of the B phase from the A phase in the viciniy of the polycritical point is explored. 
Monday, March 5, 2018 8:36AM  8:48AM 
A45.00004: The Polarphase of Superfluid ^{3}He Stabilized in Anisotropic Silica Aerogel Man Nguyen, Andrew Zimmerman, William Halperin Silica aerogel can be used to introduce disorder into superfluid ^{3}He, stablizing new phases and order parameter textures that do not occur in the pure superfluid^{1,2,3}. In particular, aerogel can be processed to have anisotropic disorder by either stretching or compressing the samples. Using NMR spectroscopy, we observe evidence for a new superfluid phase in ~20% compressed aerogel at low pressure. The magnetic susceptibility is consistent with a state where the atoms forming the Cooper pairs have aligned spin, an equalspin pairing state. In addition, the frequency shift of this new phase is greater than the Aphase frequency shift in isotropic aerogel. Finally, there is a secondorder phase transition into the Bphase at low temperature. These three observations indicate that the polar phase of superfluid ^{3}He has been stabilized at low pressure by the anisotropic disorder of the aerogel. 
Monday, March 5, 2018 8:48AM  9:00AM 
A45.00005: Liquid Helium3 as a Quantum Acoustic Metamaterial Victoria Gabriele, Kevin Bedell Acoustic metamaterials exhibit interesting properties through manipulation of the density and bulk modulus. We propose liquid Helium3 as a candidate for an acoustic metamaterial. We show this by exploiting properties of the collective sound modes, which with a specified forcing function can allow us to control the density response function. Furthermore, we will utilize the viscoelastic nature of liquid Helium3, which introduces an anisotropy that is unique in liquids(Bedell, K., Pethick, C.J. J. Low Temp. Phys. 49, 213 (1982).). This provides us with an additional way to explore enhanced absorption and negativeindex regions in Helium3. We will explore this behavior at various temperature and density ranges. 
Monday, March 5, 2018 9:00AM  9:12AM 
A45.00006: Lowenergy Effective Field Theory of Superfluid ^{3}HeB Keisuke Fujii, Yusuke Nishida The lowenergy physics of a superfluid ^{3}HeB is governed by NambuGoldstone bosons resulting from its characteristic symmetry breaking pattern. Here we construct an effective field theory at zero temperature consistent with all available symmetries in curved space, which are the U(1)_{phase}×SU(2)_{spin}×SO(3)_{orbital} gauge invariance and the nonrelativistic general coordinate invariance, up to the nexttoleading order in a derivative expansion. The obtained lowenergy effective field theory is capable of predicting gyromagnetic responses of the superfluid 3HeB, such as a magnetization generated by a rotation and an orbital angular momentum generated by a magnetic field, in a modelindependent and nonperturbative way. We furthermore show that the stress tensor exhibits a dissipationless Hall viscosity with coefficients uniquely fixed by the orbital angular momentum density, which manifests itself as an elliptical polarization of sound wave with an induced transverse component. 
Monday, March 5, 2018 9:12AM  9:24AM 
A45.00007: StrongCoupling Corrections to CollectiveMode Frequencies in Superfluid ^{3}HeB John Paliotta, Joseph Serene The frequencies of collective modes in superfluid ^{3}He in principle provide sensitive probes of the quasiparticle interactions (Landau parameters and pairing interactions), but the interpretaqtion of experiemntal results for these frequencies has always been uncertain due to unknown corrections from nontrivial strongcoupling effects (those not subsumed in the magnitude of the order parameter). We will report perturbative calculations of corrections to to the frequency of the J^{C }= 2^{+} mode of ^{3}HeB using the weakcouplingplus model of Rainer and Serene.[1] 
Monday, March 5, 2018 9:24AM  9:36AM 
A45.00008: Probing the dynamics of ^{3}He adsorbed on MCM41 with NMR Chao Huan, Naoto Masuhara, Johnny Adams, Marc Lewkowitz, Donald Candela, Neil Sullivan A one dimensional quantum gas can be realized by confining ^{3}He atoms in certain 1D nanochannels. Previously, researchers examined the dynamics of ^{3}He atoms adsorbed on the surface of the pores of mesaporous materials such as MCM41 and FSM due to their unique cylindrical pore shapes. Interesting 1D signatures were disclosed through nuclear susceptibility and nuclear relaxometry measurements. However to explore the behavior of a neutral TomonagaLuttinger liquid as predicted by theory, the sample has to be cooled down to much lower temperatures. In this preliminary experimental study, we measured the nuclear susceptibility, the spinlattice relaxation times (T_{1}) and spinspin relaxation times (T_{2}) of a single layer ^{3}He adsorbed in MCM41 over a broad temperature range of 0.032.5 K. Our results show both quantum solid and 1D Fermi gas behavior of the ^{3}He. 
Monday, March 5, 2018 9:36AM  9:48AM 
A45.00009: Bounds on hydrodynamic data from manybody quantum chaos Andrew Lucas Is the hydrodynamics of an interacting manybody system fundamentally limited by basic principles of quantum mechanics? Starting with the conjecture that viscosity is at least as large as entropy density (as measured in fundamental units), there has been a long search for a precise answer to this question. I point out a simple relationship between hydrodynamics and manybody quantum chaos in a broad class of experimentally realizable systems. Consistency with the quantum butterfly effect leads to upper bounds on the speed of sound and diffusion constants of hydrodynamics. These bounds link two very different theories of quantum manybody dynamics, clarify the relationship between classical hydrodynamics and quantum information loss, and provide a simple way to constrain theories of thermalization and quantum chaos in experiments. 
Monday, March 5, 2018 9:48AM  10:00AM 
A45.00010: Manybody chaos in a conformal gauge theory Julia Steinberg, Brian Swingle The onset of manybody quantum chaos in fermionic systems can be diagnosed from the growth of initally anticommuting fermion field operators. We compute such anticommutators of fermion field operators in (2 + 1)d U (1) gauge theory with N_{f} flavors of fermions to leading order in 1/N_{f} . For large enough N_{f} , this is an interacting conformal field theory and describes the low energy properties of the Dirac spin liquid. The anticommutator grows exponentially in time with a rate defined by the Lyapunov exponent λ_{L} and grows ballistically in space at a speed identified as the “butterfly velocity” v_{B}. The scaling with temperature is fixed by conformal invariance. We briefly comment on the growth of local current operators and the breakdown of the large N_{f} expansion. 
Monday, March 5, 2018 10:00AM  10:12AM 
A45.00011: ManyBody Chaos in the Quantum Lifshitz Model Eugeniu Plamadeala, Eduardo Fradkin We compute the parameters characterizing manybody quantum chaos in the 2+1D Quantum Lifshitz model with N flavors, specifically the Lyapunov exponent and butterfly velocity as a function of temperature, diffusion constant, and interaction strength. The quartic term added to break integrability gives logarithmic (in temperature) corrections to the naive expression for the Lyapunov exponent. Despite z=2 scaling, an effective temperaturedependent velocity is generated and chaos spreads ballistically. 
Monday, March 5, 2018 10:12AM  10:24AM 
A45.00012: Microscopic Models for Electron Hydrodynamics Thomas Scaffidi, Nabhanila Nandi, Burkhard Schmidt, Andrew P. Mackenzie, Joel Moore A novel regime of transport whereby electrons behave like a viscous fluid has been the subject of intense study over the past few years. By using various kinetic and hydrodynamic models, we will study the conditions under which such a regime can be obtained and the experimental signatures one should look for. We will show in particular that the viscous Hall effect is a very useful probe of hydrodynamic effects and that the interplay of restricted geometries and applied magnetic fields leads to extremely rich physics. 
Monday, March 5, 2018 10:24AM  10:36AM 
A45.00013: title{Hydrodynamic behavior driven by surface boundary state in Weyl semimetals}
\author{D. Schmeltzer}
\affiliation{Physics Department, City College of the City University of New York,
New York, New York 10031, USA}
% \begin{abstract
We derive a theory for the Weyl semimetal with a boundary David Schmeltzer Hydrodynamic behavior driven by surface boundary state in Weyl semimetals 
Monday, March 5, 2018 10:36AM  10:48AM 
A45.00014: Screening properties of quasielectrons in Laughlin states Hans Hansson, Eddy Ardonne, Jonas Kjäll, Maria Hermanns, Vatsal Dwivedi

Monday, March 5, 2018 10:48AM  11:00AM 
A45.00015: Superballistic flow of viscous electron fluid through graphene constrictions Denis Bandurin, Roshan Krishna Kumar, Yang Cao, Francesco Pellegrino, Marco Polini, Leonid Levitov, Andre Geim Electron–electron (e–e) collisions can impact transport in a variety of surprising and sometimes counterintuitive ways. Despite strong interest, experiments on the subject proved challenging because of the simultaneous presence of different scattering mechanisms that suppress or obscure consequences of e–e scattering. Only recently, sufficiently clean electron systems with transport dominated by e–e collisions have become available [1]. In this talk, we will discuss electron transport through graphene constrictions and show that their conductance below 150 K increases with increasing temperature [2], in contrast to the metallic character of graphene. Notably, the measured conductance exceeds the maximum conductance possible for free electrons. This anomalous behavior is attributed to collective movement of interacting electrons, which ‘shields’ individual carriers from momentum loss at sample boundaries. The measurements allow us to identify the conductance contribution arising due to electron viscosity and determine its temperature dependence. 
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