Studying Superfluids With Electromechanical Scantling

Microelectromechanical and nanoelectromechanical structures have many proposed uses; one of these is to examine quantum fluids. A quantum fluid is any liquid that can show quantum effects but on a macroscopic level that only occurs when the liquid is brought to an incredibly low temperature. Of course this macroscopic level can still be very small which is where the microelectronics come in.

One of the key aims has been to create a resonator, that when submerged in a quantum liquid would be of the same order of magnitude as the coherence of the fluid. Another key idea is the actual cooling of the nanoelectromechanical system itself. The goal of trying to make systems of millions of atoms obey quantum mechanical predictions is ever present. Plunging the structures into the quantum fluids is described as a brute force way of cooling them and such methods have only worked on higher frequency resonators in the past. One of the most basic of these resonators is simply a piece of wire. This superconducting wire will only be a few millimetres long and tens of micrometres wide. The resonance of this system, in helium-3 superfluids normally, is in the range of a few kilohertz. Even with all the fancy piezoelectric quartz oscillators and aluminium coated silicon tubes, the superconducting wire has remained the go-to probe for measuring the lowest temperatures within quatum fluids, even to tens of microkelvin in some cases. There have even been suggestions of using resonating superconducting wires as part of the sensors in dark matter detection.

Today’s paper is the first report on using nanoelectromechanical devices to study the properties of a quantum fluid in bulk. It progresses off previous studies into the nature of quantum fluids in a thin film which itself developed from just examining the vapour properties of a superfluid. The nanoelectromechanical devices were just bars of aluminium prodcued with variable lengths between 0.5 and 500 micrometres. They were mounted on a chip and suspended in helium-4 at between 1 and 4 Kelvin. Data gathering was done through magnetomotive measurement, produced by a five Tesla magnetic field permeating the liquid. Now that there is knowledge about these devices running in helium-4, helium-3, the optimal cooling agent, will soon also be examined this way.

Paper links: Operating Nanobeams in a Quantum Fluid


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