Nature:
Superconducting quantum interference devices (SQUIDs) take
advantage of the ability of electrons to tunnel through thin
insulators sandwiched between two Y-shaped superconductors.
Francesco Giazotto and María José
Martínez-Pérez of the National Enterprise for
Nanoscience and Nanotechnology (NEST) in Pisa, Italy, examined
SQUIDs' ability to transfer heat and found that magnetic fields
applied to the superconductors could control the rate of heat
flow across the insulator. The two researchers heated one end
of a SQUID and monitored the temperature of an electrode
attached to the other end while they varied the magnetic field.
They discovered that they could even make the heat flow from
the cold end to the hot end, which apparently violates the
second law of thermodynamics. As Giazotto explains it, the
apparent violation is the result of using the magnetic field to
shift the wavefunctions of the superconducting electrons. And
the net heat flow is still from warm to cold, but that normal
heat transfer does not cross the insulator barriers. The duo's
discovery proves a theory proposed in 1965 by Kazumi Maki and
Allan Griffin. While there is some question whether the
discovery will have practical applications, Giazotto believes
it could be used to develop caloritronics, circuits that
transmit information as heat, instead of electronics.
