Synopsis: On-Chip Thermometer

A tiny thermometer based on a single tunnel junction records temperatures in the millikelvin regime with a simple, compact design.
Synopsis figure
A. V. Feshchenko et al., Phys. Rev. Applied (2015)

A new micrometer-scale thermometer—small enough to fit on a computer chip—can measure temperatures as low as 7 millikelvin, which is a tenfold improvement over similar designs. The device works by monitoring the current that tunnels between a metal and a superconductor layer. With its ability to measure cryogenic temperatures, this chip-compatible thermometer might eventually be used to thermally monitor qubits in a solid-state quantum computer.

A tunnel junction consists of two conductors (metal or superconducting) separated by an insulating barrier. The rate by which electrons tunnel through the barrier is dependent on temperature. In recent years, scientists have created devices, such as the Coulomb blockade thermometer, which use tunnel junctions to measure temperature, but the tunnel configurations are often complicated and require sophisticated methods to extract a temperature reading.

Researchers from Aalto University in Finland and the University of Basel in Switzerland designed a new thermometer that can reach millikelvin temperatures with a compact experimental setup. For the core of their device, the team fabricated a 400-nanometer-wide normal-metal–insulator–superconductor (NIS) tunnel junction from thin layers of copper, aluminum oxide, and aluminum. The team measured the tunneling current (I) at different voltages (V) and then used the shape of the I-V curve to estimate the temperature of the copper layer (which also acts as the thermal contact to a sample). The temperature sensitivity is better than previous NIS-based systems because the new design provides shielding from radiation and electronic noise, while the chip layout allows efficient evacuation of dissipated heat.

This research is published in Physical Review Applied.

–Michael Schirber


Features

More Features »

Announcements

More Announcements »

Subject Areas

SuperconductivityCondensed Matter Physics

Previous Synopsis

Nuclear Physics

Throwing Nuclei in the Ring

Read More »

Next Synopsis

Optics

Shaping X-Ray Pulses

Read More »

Related Articles

Synopsis: Superfluid Storm at a Surface
Fluid Dynamics

Synopsis: Superfluid Storm at a Surface

Numerical simulations indicate that boundary layers, normally the preserve of conventional fluids flowing past solid surfaces, can also arise in superfluids.   Read More »

Focus: Magnetic Fluctuations without a Magnet
Condensed Matter Physics

Focus: Magnetic Fluctuations without a Magnet

Magnetic waves in a permanent magnet can survive even when the material is too hot for large-scale magnetism to exist. Read More »

Focus: Ultrafast Switch with Organic Crystal
Condensed Matter Physics

Focus: Ultrafast Switch with Organic Crystal

An organic crystal was switched between paraelectric and ferroelectric states in a picosecond. Similar materials could eventually serve as extremely fast digital switches. Read More »

More Articles