An exotic type of symmetry — suggested by string theory and theories of high-energy particle physics, and also conjectured for electrons in solids under certain conditions — has been observed experimentally for the first time.
An international team, led by scientists from Oxford University, report in a recent article in Science how they spotted the symmetry, termed E8, in the patterns formed by the magnetic spins in crystals of the material cobalt niobate, cooled to near absolute zero and subject to a powerful applied magnetic field.
The material contains cobalt atoms arranged in long chains and each atom acts like a tiny bar magnet that can point either ‘up’ or ‘down’.
When a magnetic field is applied at right angles to the aligned spin directions, the spins can ‘quantum tunnel’ between the ‘up’ and ‘down’ orientations. At a precise value of the applied field these fluctuations ‘melt’ the ferromagnetic order of the material resulting in a ‘quantum critical’ state.
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