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| Electricity can run between two superconductors even through electrically insulating barriers (yellow). Now researchers have found that a magnetic field (curved arrows) can switch the amount of heat that flows from a hot side (red) to a cold one (blue). |
The strange world of quantum mechanics just got a little stranger with the discovery that a magnetic field can control the flow of heat from from one body to another. First predicted nearly 50 years ago, the effect might some day form the basis of a new generation of electronic devices that use heat rather than charge as the information carrier.
The research stems from the work of physicist Brian Josephson, who in 1962 predicted that electrons could 'tunnel' between two superconductors separated by a thin layer of insulator — a process forbidden in classical physics. The Josephson junction was subsequently built and used to make superconducting quantum interference devices (SQUIDs), which are now sold commercially as ultra-sensitive magnetometers.
In the latest work, Francesco Giazotto and María José Martínez-Pérez at the NEST nanoscience institute in Pisa, Italy, measured the devices’ thermal behaviour — that is, how the electrons inside them transfer heat. The duo heated one end of a SQUID several micrometres long and monitored the temperature of an electrode connected to it. A SQUID consists of two y-shaped pieces of superconductor joined together to form a loop, but with two thin pieces of insulating material sandwiched in between (see figure); as the researchers varied the magnetic field passing through the loop, the amount of heat flowing through the device also changed. The effect was in line with a theory put forward by Kazumi Maki and Allan Griffin in 1965.
Nature: Magnetism flips heat flow
Validation of long-predicted quantum effect points the way to thermal electronics.
Edwin Cartlidge
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