Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session C44: Helium-3 and Helium-4 Low Temperature PropertiesLive
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Sponsoring Units: DCMP Chair: Paul Sokol, Indiana Univ - Bloomington |
Monday, March 15, 2021 3:00PM - 3:12PM Live |
C44.00001: Measuring the macroscopic angular momentum in 3He-A via superfluid sound Stefan Forstner, Christopher G Baker, Glenn I Harris, Andreas Sawadsky, Hyoungsoon Choi, Warwick Bowen
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Monday, March 15, 2021 3:12PM - 3:24PM Live |
C44.00002: Effect of the boundary condition on the Kapitza resistance between superfluid 3He-B and sintered metal Richard Haley, Samuli Autti, Asher Jennings, George Pickett, Roch Schanen, Arkady Soldatov, Viktor Tsepelin, Jakub Vonka, Dmitry Zmeev Understanding the temperature dependence of the thermal boundary resistance, or Kapitza resistance, between liquid helium and sintered metal has posed a problem in low temperature physics for decades. In the ballistic regime of superfluid 3He−B we find the Kapitza resistance can be described via scattering of thermal quasiparticle excitations with a macroscopic geometric area rather than the sintered metal's microscopic area. We estimate that a quasiparticle needs on the order of 1000 collisions to successfully thermalize with the sinter. Finally, we find that the Kapitza resistance is approximately doubled with the addition of two monolayers of solid 4He on the sinter surface, which we attribute to an extra magnetic channel of heat transfer closing as the nonmagnetic solid 4He replaces the magnetic solid 3He. |
Monday, March 15, 2021 3:24PM - 3:36PM Live |
C44.00003: Heat Transport in Superfluid 3He in Anisotropic Aerogel Priya Sharma, James Sauls We report new theoretical results for heat transport by quasiparticle excitations in superfluid 3He infused into silica aerogel engineered with uniaxial anisotropy. For this system two distinct equal spin pairing (EPS) superfluid phases have been reported based on NMR spectroscopy [1]. Theoretical analysis predicts the first ESP state to be the chiral A phase with chiral axis aligned along the strain axis, and the lower temperature phase to be a polar-distorted chiral phase with random transverse fluctuations in the orientation of the chiral axis [2]. We report calculations of heat transport for these two chiral phases, including anomolous thermal Hall effects originating from branch conversion scattering of Bogoliubov quasiparticles by the chiral order parameter induced by potential scattering by the silica aerogel. |
Monday, March 15, 2021 3:36PM - 3:48PM Live |
C44.00004: Spectroscopy of surface Majorana fermions in superfluid 3He-B using a mechanical oscillator Takeshi Mizushima, Wataru Mori The superfluid 3He-B is a prototype of DIII topological superconductors, which hosts helical Majorana fermions on the surface. As a consequence of the chiral symmetry, Majorana fermions show uniaxially anisotropic magnetic response, and only a particular orientation of a magnetic Zeeman field can generate the mass gap, which is referred to as Majorana Ising spins. Recently, P. Zheng et al. [Phys. Rev. Lett. 117, 195301 (2016)] observed the anomalous damping of a microelectromechanical system (MEMS) device immersed in the superfluid 3He-B. Here we investigate the damping mechanism of a laterally oscillating plate in the topological superfluid 3He, and clarify the roles of surface Majorana fermions. Using the quasiclassical Keldysh transport theory together with a random S-matrix model, we calculate the stress tensor on the surface of a laterally oscillating plate embedded in 3He-B. We demonstrate that the low-temperature behaviors of the damping rate are sensitive to surface specularity and mass gap induced by magnetic Zeeman fields. The power law of the damping rate in low temperatures may provide spectroscopy for the mass gap of surface states and the topological phase transition in the superfluid 3He-B. |
Monday, March 15, 2021 3:48PM - 4:00PM Live |
C44.00005: Low temperature dynamics of quasi-1d 3He: NMR studies Chao Huan, Johnny Adams, Marc Lewkowitz, Naoto Masuhara, Lucia Steinke, Donald Candela, Neil Samuel Sullivan We explore Luttinger liquid behavior of 3He constrained to nanochannels in mesoporous MCM-41, thermalized using silver powder. The inner diameter of the channels (2.1 nm) is further reduced by preplating with 4He to provide quasi-1D channels for the 3He motion. 3He was added to create a line density of 1.0 nm-1 that has an estimated Fermi temperature of 120 mK. We measure the temperature dependence of the nuclear spin-lattice and spin-spin relaxation times at sample temperatures down to the low temperature limit of 40 mK imposed by Kapitza resistances. The results are compared with the expectations for Luttinger liquid behavior for which a peak is expected in the nuclear spin-lattice relaxation time at 2TF. |
Monday, March 15, 2021 4:00PM - 4:12PM Live |
C44.00006: The Effect of Leggett–Takagi Relaxation on Vortex-Generated Spin Waves in Superfluid 3He-B Sami Laine, Erkki V Thuneberg Vortices in the B phase of superfluid 3He can excite spin waves, leading to experimentally observable relaxation of uniformly precessing magnetisation [1,2,3]. Here, we study the phenomenon at intermediate temperatures T∼0.5 Tc within the framework of Leggett–Takagi theory [4] by solving the equations of spin dynamics for an isolated vortex line in the absence of spin diffusion and calculating the energy relaxation rate. There are two factors contributing to the relaxation: excitation of spin waves by the vortex and the intrinsic Leggett–Takagi mechanism stemming from conversion of spin between Cooper pairs and quasiparticles. Under conditions relevant to the experiment in Ref. [1], we find that spin wave radiation is the dominant effect. One noteworthy consequence of the Leggett–Takagi mechanism is attenuation of spin waves at distances less than the typical inter-vortex separation, justifying our assumption that vortices can be treated independently of each other. |
Monday, March 15, 2021 4:12PM - 4:24PM Live |
C44.00007: X-Ray Imaging of the Phase Separation in Mixed 3He/4He Nanodroplets Sean O'Connell, Deepak Verma, Alexandra J Feinberg, Swetha Erukala, Catherine A Saladrigas, Benjamin W Toulson, Mario Borgwardt, Niranjan Shivaram, Ming-Fu Lin, Andre Al Haddad, Wolfgang Jaeger, Christoph Bostedt, Peter Walter, Oliver Gessner, Andrey F. Vilesov A mixture of 3He and 4He liquids separates into a 3He-rich and a 4He-rich phase below 0.87 K. Here, we present a study of this phase separation in freely-rotating, sub-micrometer-sized helium droplets under molecular beam conditions in vacuum at T ≈ 0.15 K. Density distributions within individual droplets are studied by ultrafast x-ray diffraction using the LCLS free electron laser. Strong indications for the separation of the two phases within the droplet are provided by pronounced azimuthal intensity modulations of the ring-shaped diffraction patterns, that the inner phase has a different shape than the outer one. We examine the possibilities that the 4He rich phase may consists of two lobes or a torus immersed in 3He. The results are also compared to recent theoretical work on phase separation in classical rotating droplets [1] and DFT calculations on mixed 3He/4He droplets [2]. |
Monday, March 15, 2021 4:24PM - 4:36PM Live |
C44.00008: Specific heat of a thin 4He film on graphite Massimo Boninsegni, Saverio Moroni
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Monday, March 15, 2021 4:36PM - 4:48PM Live |
C44.00009: Cluster Aggregation in Bosonic and Fermionic Helium Nanodroplets Alexandra Feinberg, Deepak Verma, Sean O'Connell, Swetha Erukala, Rico Tanyag, Weiwu Pang, Catherine Saladrigas, Benjamin W Toulson, Mario Borgwardt, Niranjan Shivaram, Ming-Fu Lin, Andre Al Haddad, Wolfgang Jäeger, Christoph Bostedt, Peter Walter, Oliver Gessner, Andrey F. Vilesov Bosonic superfluid helium-4 droplets obtained in molecular beams have sizable angular momentum, which manifests itself physically in the form of quantized vortices. In our previous works, vortices have been visualized via ultrafast X-ray coherent diffractive imaging using xenon as a contrast agent. Xenon atoms are attracted to the vortex cores leading to the formation of filament – shaped clusters [1]. Here, we study the formation of clusters in non-superfluid fermionic helium-3 droplets, which also rotate but are devoid of any quantum vortices. It was found that in distinction to helium-4, xenon atoms inside helium-3 form loose aggregates arranged into rings on the periphery of the droplets. This is because in normal fluid helium-3 droplets, dopants are fixed in the rotating frame. Thus, heavy xenon atoms are pushed to the droplets’ periphery by centrifugal forces where they recombine into ring-shaped structures. |
Monday, March 15, 2021 4:48PM - 5:00PM Live |
C44.00010: Tuning the quantumness of simple Bose systems and the evolution of the phase diagram Youssef Kora, Massimo Boninsegni, Dam Thanh Son, Shiwei Zhang By means of first-principle Quantum Monte Carlo simulations, we study systems of Bose particles interacting via the Lennard-Jones interaction, which constitute a broad class of condensed matter systems that ranges from crystals to normal fluids to superfluids and gases. The interplay between particle interactions on the one hand, and quantum indistinguishability and delocalization on the other, is characterized by a single quantumness parameter. We show how the topology of the phase diagram evolves from the familiar case of He-4 as the dynamics of the particles become more (and less) quantum. We compare our predictions with available results from mean-field theory, and we discuss possible experimental realizations of the phases and physical regimes predicted here, including hypothetical muonic matter. |
Monday, March 15, 2021 5:00PM - 5:12PM Live |
C44.00011: Suppression of triplet superfluidity near magnetically-active surfaces Anton Vorontsov Recent experiments investigating properties of the chiral A phase of superfluid He-3 in thin slabs (P. Heikkinen et al, arXiv:1909.04210) revealed unusually large Tc suppression that exceeds the fully-diffusive scattering limit. This requires re-thinking of the boundary conditions, and inclusion of magnetic degree of freedom to describe scattering of the quasiparticles on surfaces that are covered my magnetically-active solid layer of He-3 atoms. I will review existing models of magnetic scattering to prove that they cannot, in principle, give such suppression of the A phase. I will show that in order to explain the large Tc suppression, the internal quantum degrees of freedom of the solid spins have to be taken into account. |
Monday, March 15, 2021 5:12PM - 5:24PM Live |
C44.00012: Functional Renormalization Group Study of Correlated Bose-Einstein Systems -- Low-Temperature Properties of Specific Heat Akimitsu Kirikoshi, Takafumi Kita Greywall's measurement[1] on the specific heat of the superfluid 4He exhibit deviations from the T3-law predicted by the Landau theory. This system belongs to the Bose-Einstein condensates (BECs) where correlations are strong. |
Monday, March 15, 2021 5:24PM - 5:36PM Live |
C44.00013: Coupling of Pair Fluctuations to Zero Sound: A Field Theoretical Approach Wei-Ting Lin, James Sauls In a seminal paper Paulson and Wheatley reported measurements of enhanced attenuation of zero sound in liquid He-3 at temperatures just above the onset of the superfluidity [1]. Here we report new results based on a field-theoretical formulation of the coupling of Cooper pair fluctuations and zero sound. Our theory is based on a functional integral formulation of interacting fermions. By introducing auxiliary bosonic fields to describe the zero sound and pair fluctuations, we obtain the collisionless Boltzmann-Landau equation for zero sound and the GL theory for the pair fluctuations. In addition we obtain the leading order interactions between these two bosonic excitations which give corrections to the Boltzmann-Landau equation, and thus the dispersion relation of zero sound. The corrections have a structure similar to those in the theory of paraconductivity which cause the increase of conductivity due to pair fluctuations at temperatures just above the superconducting phase transition. We discuss the implications of our theory, and comment on the report on attenuation of zero sound proposed by Samalam and Serene [2]. |
Monday, March 15, 2021 5:36PM - 5:48PM Live |
C44.00014: Non-linear Dynamics of the Trapped Quantum Vortex Joe Depellette, Callum Hayward, Andrew Guthrie, Sergey Kafanov, Nathaniel Morrison, Mark Theodore Noble, Yuri Pashkin, George Pickett, Viktor Tsepelin Nanomechanical resonators have recently been studied as high-sensitivity probes of fluid dynamics in superfluid helium [1, 2, 3]. When turbulence is introduced to such a system, quantum vortices may form and become trapped by the resonator, either completely surrounding the oscillating beam (a fully trapped vortex) [4] or surrounding only part of it (a partially trapped vortex). Fully trapped vortices have been studied using the model of a linear harmonic oscillator behaviour with great success [4]. However, in the presence of a partially trapped vortex, the oscillators have been found to behave non-linearly. We analysed the non-linear response of a doubly clamped nanobeam resonator submerged in helium-4 at 10 mK in the presence of a partially trapped vortex. Our analysis demonstrates that the observed non-linearities are caused by the dynamics of the vortex line. |
Monday, March 15, 2021 5:48PM - 6:00PM Live |
C44.00015: Possible coexistence of Superfluidity and Spatial Order in Monolayers of Helium-4 JUN USAMI, Ryo Toda, Hiroshi Fukuyama The superfluidity coexisting with the spatial order is predicted in the proposed quantum liquid crystal (QLC) phase of the 2nd monolayer of 4He on graphite from the heat capacity (HC) [1] and the torsional oscillator (TO) studies [2]. So far, it is not clear if the QLC phase, which exists within a small density region (9%) between the liquid and solid phases, shows the superfluidity due to large uncertainties in determination of the sample density (r). Recently, we succeeded in eliminating this problem by carrying out simultaneous HC and TO measurement on the same samples. The results show unambiguously finite frequency (f) shifts due to superfluidity in the QLC phase at T < 0.3 K. Also found is that the coefficient of the background T-linear dependence of f (T) at T > 0.3 K starts to increase once the thermodynamic characteristic of the QLC phase appears in the HC measurement with increasing r. This can be attributed to stiffening of the 4He and graphite composite, being consistent with the partial spatial order in the QLC phase. |
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