QFS2016 Book of Abstracts

Abstracts

P4.12

Sub-superfluid 3-He coherence length cross-section SiNN (Silicon

Nitride – Niobium) wires.

De Alba, R(1), Abhilash T.S(1), Rand R.(2) and Parpia, J.M.(1)

1) Department of Physics, Clark Hall, Cornell University, Ithaca NY 14850

USA

2) Department of Mathematics, Malott Hall, Cornell University, Ithaca NY

14850 USA

We report on the room temperature characterization of ultrafine composite wires

formed of high stress Silicon Nitride onto which a film of superconducting Nb was

evaporated. The wires’ cross section (50 nm square) is less than the coherence

length of superfluid

He. We describe the fabrication details of the wires, together

with room temperature characterization of the resonant frequency and Q of the

wires with and without the additional Nb layer. Further we will describe the

so-called “self oscillation regime” where these devices execute harmonic motion

when illuminated with intense laser light. We observe stable limit-cycle behavior

with an amplitude of roughly one-eighth of the impinging laser wavelength, and

characterize entrainment of this motion with inertial forcing. Such parametric

drive implemented with double-frequency driving force may enable these devices

to be operated in the viscous as well as ballistic regimes in norml and superfluid

He.

P4.13

The influence of high magnetic field on resonant characteristics of

high Q-value quartz tuning fork in vacuum in milikelvin temperature

range

ˇCloveˇcko Marcel, Kupka Martin, Skyba Peter, Vavrek Frantiˇsek

Centre of Low Temperature Physics, Institute of Experimental Physics, SAS and

P. J. ˇSaf´arik University Koˇsice, Watsonova 47, 04001 Koˇsice, Slovakia

We have extensively studied the influence of high magnetic field (up to 8 Tesla) on

vacuum resonant characteristics of a commercially available 32 kHz quartz tuning

fork in millikelvin temperature range. High magnetic field applied perpendicularly

to both the direction of oscillations and piezoelectric current generates additional

force acting on oscillating electric dipoles inside quartz. This additional force (as

a possible source of de-coherence) effectively stiffens the quartz crystal manifested

by the rise of resonance frequency and simultaneously decreases its electrical

conductivity which leads to additional dissipation. We discuss a physical origin

of the observed phenomenon.

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