Ultrasonic interferometer for first-sound measurements of confined liquidHe4

Abstract

We present a new technique for probing the properties of quantum fluids in restricted geometries. We have confined liquid 4 He within microfluidic devices formed from glass wafers, in which one dimension is on the micro scale. Using an ultrasonic analog to Fabry-Pérot interferometry, we have measured the first-sound of the confined liquid 4 He, which can be a probe of critical behavior near the lambda point (T λ ). All thermodynamic properties of liquid 4 He can be derived from first-sound and heat capacity measurements, and although quite a bit of experimental work has been done on the latter, no measurement of first-sound has been reported for a precisely confined geometry smaller than a few tens of micrometers. In this work, we report measurements of isobaric first-sound in liquid 4 He confined in cavities as small as ∼ 5 µm. Our experimental setup allows us to pressurize the liquid up to ∼ 25 bar without causing deformation of the confined geometry, a pressure which is about four times larger than previously reported with similar microfluidic devices. Our preliminary results indicate that one can possibly observe finite-size effects and verify scaling laws, by using similar devices with smaller confinement.

Acoustic Signatures of the Phases and Phase Transitions in the Blume Capel Model with Random Crystal Field

“…Similar temperature dependence of the sound dispersion has been reported near the order-disorder phase transition point of the BEG model [47]. Comparably, the existence of the minima of the sound velocity in the ordered phase and its shift to lower temperatures with increasing frequency have been observed in the classical liquid crystals [8], liquid 4 He confined in a microfluidic cavity [10], and the magnetic compound RbMnF 3 [48]. In addition, it can be seen from Figure 1 that the change in sound velocity becomes frequency-independent as one approaches to critical value of the reduced temperature and this behavior is in parallel with the findings of the molecular field theory [17,49], dynamical renormalization group theory for the propagation of sound near the continuous structural phase transitions [50], and Brillouin scattering studies of A 2 MX 6 -crystals [49].…”

“…Investigation of nonequilibrium processes probed by ultrasound waves in the spin-ice materials such as Yb 2 Ti 2 O 7 and Dy 2 Ti 2 O 7 [4,5] and the frequency-dependent anisotropy of sound velocity and attenuation of the acoustic wave propagation through the nematic liquid crystals [6][7][8] represent examples to studies that are related to ultrasonic propagation in systems that undergo phase transitions. Further, considerable attention has been focused on the investigation of sound attenuation in disordered conductors [9]: the behavior of sound propagation near the point of the confined liquid 4 He [10][11][12][13] and absorption of ultrasound near the critical mixing point of a binary liquid [14][15][16]. Finally, one should note that a great variety of magnetic materials including halides, metals, oxides, intermetallics, and sulphides exhibit anomalies in their elastic properties due to the fact that orderdisorder transitions are typically accompanied by small lattice distortions [17].…”

Superfluid nanomechanical resonator for quantum nanofluidics

“…1e in a liquid 4 He bath sealed in a copper sample cell mounted on a cryostat. The device consists of features etched into glass, where the etch height defines the relevant confinement length 26,27 . Specifically, we form a circular cavity (radius r cav = 2.5 mm and height h cav = 1100 nm) and four channels (length l cha = 2.5 mm, width w cha = 1.6 mm and height h cha = 550 nm).…”

Superfluid Optomechanics With Phononic Nanostructures

“…A schematic of the nanofabrication process steps is shown in Fig. 8, more details of this type of fabrication process can be found at references [28,[30][31][32]. Using optical lithography techniques, we can easily pattern micron sized planar geometries on a substrate (e.g.…”

“…In the present work, we propose a novel architecture for superfluid optomechanics, based on engineered nanostructures allowing a better control over superfluid phonon propagation, preserving superfluid 4 He's exceptional intrinsic properties, and leading to enhanced quality factors and coupling strengths. Exploiting recent progress in quantum nanofluidics, concerning the confinement at the nanoscale of quantum fluids (liquid helium-4 [27][28][29][30][31][32][33][34] and liquid helium-3 [29,[35][36][37][38][39][40]), one can form a nanoscale cavity of typically hundreds of nm in height, and tens of µm in width defining the boundaries of a picogram or femtogram scale superfluid acoustic resonator [30][31][32]. Such superfluid acoustic resonator could be formed by means of a microsale hollow volume within a glass or silicon substrate.…”