There and back again: from magnets to superconductors Date: Wednesday, November 25, 2009 @ 23:00:40 UTC Topic: Science
Interactions often modify the behavior of quantum particles and
reorganize them into new phases of matter. One dramatic example is the
superconducting state, where electrons with attractive interactions
form Cooper pairs. The most pertinent interactions in metals are often
effective ones—mediated by lattice vibrations and magnetism—and they
can be altered by changing the electron environment. Changes to
chemical composition, applying magnetic fields and or pressure have the
most dramatic effect on the interactions near a so-called quantum
critical point [1].
This is the point in the phase diagram where, at zero temperature, a
metal is just on the verge of developing magnetic order.
In this vicinity electrons interact via intense quantum and thermal
fluctuations of that incipient order. Those long-range interactions
both modify the metallic properties and also lead to new
low-temperature phases such as superconductivity. In a paper in Physical Review Letters [2],
Gareth Conduit and Ben Simons at the Cavendish Laboratory in Cambridge
and Andrew Green at the School of Physics and Astronomy at St. Andrews,
both in the UK, undertake a theoretical study of metals near a
ferromagnetic quantum critical point. They show that critical
fluctuations there can favor a low-temperature phase that is the
magnetic analog of a superconducting state...
Interactions often modify the behavior of quantum particles and
reorganize them into new phases of matter. One dramatic example is the
superconducting state, where electrons with attractive interactions
form Cooper pairs. The most pertinent interactions in metals are often
effective ones—mediated by lattice vibrations and magnetism—and they
can be altered by changing the electron environment. Changes to
chemical composition, applying magnetic fields and or pressure have the
most dramatic effect on the interactions near a so-called quantum
critical point [1].
This is the point in the phase diagram where, at zero temperature, a
metal is just on the verge of developing magnetic order.