Field-induced electronic phase transitions in high magnetic fields

We report on recent experiments on (TMTSF)₂PF₆ under high and precisely aligned magnetic fields, moderate pressure and low temperature. The primary effect of the magnetic field is to reduce the electronic dimensionality of the system. This leads to some novel states which are now understood (a cascade of field-induced spin-density-wave states which exhibit the quantum Hall effect) and to many phenomena which suggest even more exotic phases. In particular, at low temperature the compound shows quantum phase transitions between metallic and non-metallic behaviour as the magnetic field is rotated through alignment with the crystallographic axes, and the superconducting critical field greatly exceeds the Pauli limit, indicating triplet superconductivity.