Atomically thin superfluid helium films on solid hydrogen

Shirron, P. J.; Mochel, J. M.

doi:10.1103/physrevlett.67.1118

Cited by 57 publications

(26 citation statements)

References 19 publications

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“…Shirron and Mochel [6] observed a dead layer of about y monolayer in very thin films with transition temperatures near 0.2 K. Zimmerli, Mistura, and Chan [7] have reported superfluidity only above 1 layer in thicker films with transition temperatures between 0.65 and 1 K. Finally, Brisson, Mester, and Silvera [18] have observed superfluidity only above 2 helium layers in films thicker than 2.5 layers. We believe that all of these results may be consistent with the coverage dependence of the apparent Fh dead layer shown in Fig.…”

Section: The Dynamics Of the Superfluid Transition [14] Are Determinementioning

confidence: 91%

“…Naturally, this has spurred widespread interest in the nature of thin-film superfluidity on inert surfaces. Recent measurements of superfluid density on solid H2 using third sound have been particularly compelling, with reports of submonolayer superfluidity [6], coverage-induced third-sound velocity modulations [6,7], and the appearance of a possible new superfluid phase in submonolayer films [8]. To this date, however, there have been no mechanical oscillator measurements of superfluidity on weak binding substrates.…”

Section: Recent Investigations Of the Interaction Ofmentioning

confidence: 99%

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Superfluid transition inHe4films on hydrogen and its effect on the film-vapor coupling

Adams

Pant

1992

Phys. Rev. Lett.

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We have measured the 2D 4 He superfluid density o x on hydrogen using a high-(? Al oscillator. We find that only a j layer of helium remains normal well below the transition on hydrogen as opposed to 4 layers on bare Al. For transition temperatures TV below 0.9 K we find that a. s (T c ) <* TV as predicted by Kosterlitz-Thouless theory. For transitions above 1 K, where there is significant vapor damping, we see a striking suppression of

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Section: The Dynamics Of the Superfluid Transition [14] Are Determinementioning

confidence: 91%

Section: Recent Investigations Of the Interaction Ofmentioning

confidence: 99%

Superfluid transition inHe4films on hydrogen and its effect on the film-vapor coupling

Adams

Pant

1992

Phys. Rev. Lett.

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“…The physical structure of the resonator provides a template for the self-assembling film, acting to confine third sound modes at microscale in two dimensions, while their radial dimension is determined by the film thickness. Third sound modes have been observed in helium films thinner than a single atomic layer (152), providing the prospect for extremely low effective mass.…”

Section: Superfluid Optomechanics With Thin Filmsmentioning

confidence: 98%

“…Superfluid films form naturally on surfaces due to the combination of ultra-low viscosity and attractive van der Waals forces. Excitations in such films, known as third sound (50,70,122,152), manifest as perturbations to their thickness with the restoring force provided by the van der Waals interaction. The physical structure of the resonator provides a template for the self-assembling film, acting to confine third sound modes at microscale in two dimensions, while their radial dimension is determined by the film thickness.…”

Section: Superfluid Optomechanics With Thin Filmsmentioning

confidence: 99%

“…In contrast, superfluid films feature strong phonon-phonon interactions and a nonlinear van der Waals restoring force which scales as film thickness to the inverse fourth power. Further, they can have sub-monolayer thickness, comparable with the amplitude of motion (152), such that nonlinearities dominate the mechanical dynamics (70).…”

Section: Duffing Nonlinearitymentioning

confidence: 99%

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Cavity optomechanics with feedback and fluids

Harris¹

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Mechanical oscillators are extensively used in applications ranging from chronometry using quartz oscillators to ultra fast sensors and actuators as in atomic force microscopy and spin/mass/force sensing. The continuous push towards miniaturized high precision sensors has motivated the development of increasingly high quality mechanical oscillators at length scales as small as nanometers, with integration into cryogenic environments used to avoid thermal noise. This raises the prospect of observing mechanical oscillators in a new regime where their dynamics are dictated by quantum, rather than classical, mechanics. Utilizing the quantum behaviour of mechanical oscillators promises to enhance applications in sensing and metrology. In this thesis experimental techniques are reported that enhance optomechanical sensors and enable fundamental experiments in quantum optomechanics. In particular, there is a strong emphasis towards experimentally developing detection based feedback control techniques, for example to enable feedback cooling towards the mechanical ground state or to stabilize parasitic instabilities. In addition to these experimental advances, I detail a real-time estimation strategy that invalidates the use of linear feedback to enhanced the performance of linear optomechanical sensors. Finally, a unique and promising optomechanical systems is developed and characterized based on surface waves of a thin film of superfluid helium-4.The first topic considered in this thesis is feedback cooling of a generalized optomechanical system. In that chapter a detailed mathematical treatment is derived that highlights the importance of using a dual probe position measurement to accurately characterize a feedback cooled oscillator. The theoretical results are then experimentally verified using a microtoroidal resonator controlled via electrostatic actuation. This chapter provides a brief introduction into feedback cooling and serves to introduce the fundamental optomechanical system that underscores the majority of the work presented in this thesis. In the following chapter, the problem of estimating an unknown force driving a linear oscillator is considered. In this context it is well known that linear feedback control can improve the performance of nonlinear mechanical sensors. However, for completely linear systems, feedback is often cited as a mechanism to enhance bandwidth, sensitivity or resolution. For such systems it is shown that as long as the oscillator dynamics are known, there exists a real-time estimation strategy that reproduces the same measurement record as any arbitrary feedback protocol. Consequently, some form of nonlinearity is required in the controller, plant, or sensor, to gain any advantage beyond estimation alone. This result holds true in both quantum and classical systems, with non-stationary forces and feedback, and in the general case of non-Gaussian and correlated noise. As a proof-of-principle, a specific case of feedback enhanced incoherent force resolution is experimentally ...

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