Superphenomena in solid Helium-4

Transcription

1 Superphenomena in solid Helium-4 Lode Pollet main collaborators: Anatoly Kuklov Boris Svistunov Nikolay Prokofev

2 torsional oscillators ϕ Be-Cu torsion rod Al shell Mg s < 1 6 He reasons: design, elasticity effects

3 the knobs" Perfect crystal: huge zero point motion, yet insulator Temperature: range from few mk to few K Defects : vacancies: activation energy > 1K dislocations: can be superfluid or insulating grain boundaries: can be superfluid or insulating He-3 impurities: ppm to ppb range, but big impact; for higher concentrations phase separation He3 impurities can bind to dislocations with Eb ~.8K (macrolevel) and block superflow (microlevel) not understood

4 (reversible) giant plasticity anisotropic (gliding of dislocations in basal planes) 3 million Burger vectors per second ultrapure crystal Ariel Haziot, Xavier Rojas, Andrew D. Fefferman, John R. Beamish, and Sébastien Balibar, Phys. Rev. Lett. 11, 3531 (213)

5 mass supertransport Ye. Vekhov, W. Mullin, R. Hallock, arxiv: (213) Umass sandwich (group of R. Hallock) R1 V1 vycor rods R2 V2 C1 solid C2 some flow characteristics compatible with 1d flow

6 Quantum dislocations y z Peierls barrier glide : kinks climb : jogs = aa y(x, t) = n(x, t) a a =mass transport x a semiclassical tunneling rate: 1 r u ma 2 e S (u: interatomic potential, m atomic mass) S N u/e (1K)/(~! D ) 1 ie, tunneling time below.1 ns

7 isochoric compressibility (syringe effect) (simplified) = aa S = Z + Z d dx[ Z i y + s 2 (@ x ) 2 µ y] dx[ n 1v 2 d 2 (@ xy) 2 u cos( 2 y a )] superfluid phase and displacement are conjugate vibrating string (Granato-Lucke) subject to Peierls potential at high T or for rough dislocations (slanted dislocation forest): cos(.) is irrelevant; this predicts: y / L 2 µ superclimb; anomalous isochoric compressiblity! q 2 K L spectrum of superfluid excitations is not soundlike Luttinger parameter depends on pinning length picture of quantum liquids of kinks and jogs phenomena of giant plasticity and syringe effect are related, but nevertheless quite different!

8 cylindrical nanopore y[a] x[a] strong attraction to the wall Del Maestro, Affleck, Boninsegni: Luttingerliquid at SVP we investigate systematic increase in chemical potential

9 cylindrical nanopore N huge hysteresis loop y[a] y[a] 2 CSS local melting: there is a disclination with Frank index n=1 in the center of the pore (the c-axis wraps around the symmetry axis) CS x[a] the local melting reduces the splay x[a] µ

10 y [A] cylindrical nanopore z[a] 15 Unrolling the concentric circles estimate: hcp structure stable for R>3A yields positions identical to hcp l[a]

11 cylindrical nanopore densities [A -3 ] y[a] 25 µ= 3.Κ n(r) in the CSS Phase there is simultaneous density and superfluid order x[a].2 c-map r [A]

12 cylindrical nanopore ρ s [a.u.] bulk SF CSS the superfluid order can persist to immense pressure 2 1 surface SF CS µ [K]

13 cylindrical nanopore 1. (2), q=2.16 A -1 S(q) [a.u].8.6 (11), q=2.34 A -1 the structure factor gives a main peak close to hcp and is not inconsistent with experiments CSS, µ=7.1κ.4 (1), q=2.4a -1 CS, µ=7.1κ q [A -1 ]

14 UMass sandwich setup how the flow connects and flows through (the defects of) the crystal???? He3 impurities??????

15 Conclusions No indication of bulk supersolidity in torsional oscillators it s all about topological defects Novel effects: Giant plasticity dc Mass superflow (UMass sandwich setup) syringe effect quantum liquid state of kinks and jogs interactions between dislocations, He3 impurities, grain boundaries not understood vycor, nanocylinders, with Helium should be understood from the topological defect (disclination)