Synopsis: The Coolest Microfridge

A new micrometer-sized electronic cooling device features lower temperatures and higher cooling power than previously demonstrated schemes.
Synopsis figure
Hung Nguyen/Hanoi University of Science

Cutting-edge electronic cooling devices work by having hot electrons tunnel from a metal to a superconductor, carrying heat with them. A new design, which has a “drain” for removing hot particles in the superconductor, has cooled a micrometer-sized metal slab from 150 millikelvin (mK) to a record temperature of less than 30 mK. Devices based on this scheme could potentially be installed directly on a chip for cooling qubits or ultrasensitive low-temperature detectors.

The basic structure in these electronic coolers consists of two NIS (normal metal-insulator-superconductor) junctions. When voltage is applied, relatively high-energy (hot) electrons flow out of the metal and into one superconductor, while lower-energy (cooler) electrons flow in from a second superconductor. Using this technique, previous work has been able to cool a small metal piece from 100 to 40 mK. However, the scheme’s cooling potential is diminished by heat leaking back into the metal, in particular, from hot “quasiparticles” (electron-hole pairs) that reside in the superconductors.

Jukka Pekola of Aalto University School of Science, Finland, and his colleagues explored different ways to reduce heat leakage in their aluminum-based cooling devices. First, they isolated the metal from the device substrate by placing it on top of the superconductor leads. Second, they connected each superconductor to a metal (aluminum-manganese) strip, acting as a quasiparticle drain. If a hot quasiparticle enters the drain, it rapidly loses its heat to phonons in the crystal. Thanks to this heat draining, the team’s cooling devices not only go to lower temperatures but also have much higher cooling power (heat removed per time) than other designs.

–Michael Schirber

This research is published in Physical Review Applied.


Announcements

More Announcements »

Subject Areas

SuperconductivitySemiconductor PhysicsMaterials ScienceElectronics

Previous Synopsis

Next Synopsis

Atomic and Molecular Physics

Quantum Fluctuations Affect a Row of Distant Ions

Read More »

Related Articles

Viewpoint: How to Fracture a Fluid
Fluid Dynamics

Viewpoint: How to Fracture a Fluid

High-speed imaging shows that fluids can break like brittle glass under the right conditions. Read More »

Synopsis: So Many Cracks, So Little Time
Fluid Dynamics

Synopsis: So Many Cracks, So Little Time

Water droplets impacting a cold surface exhibit a variety of fracture patterns depending on the temperature of the surface. Read More »

Synopsis: Ultrafast Switching in a Phase-Change Material
Condensed Matter Physics

Synopsis: Ultrafast Switching in a Phase-Change Material

New experiments show that picosecond pulses of light can effectively switch off the resistance in phase-change materials that are used for storing computer information. Read More »

More Articles