Figure 1

Figure 1: There are many parallels between superconductivity and forms of magnetism. (a) The FFLO state is a superconductor where the phase of the Cooper-pair wave function varies in space periodically. (b) Conduit et al. find that ferromagnetic fluctuations can favor a magnetic analog of the inhomogeneous FFLO state where the spin orientation varies in space. A simple s-wave superconductor (c) has the same Cooper-pair phase around the Fermi surface and is analogous to the simple ferromagnet which has an excess of, say, up spin around the Fermi surface (d). More exotic superconductors like the d-wave state (e) where the Cooper-pair phase changes sign around the Fermi surface are often stabilized near quantum critical points. Their corresponding magnetic states—like the spin nematic (f) where the excess spin direction changes sign around the Fermi surface—might also compete for stability.