Blue Quantum Fog: Chiral Condensation in Quantum Helimagnets

It is shown that a condensation transition involving a chiral order parameter can occur in itinerant helimagnets, in analogy to the transition between the isotropic phase and the phase known as blue fog or blue phase III in cholesteric liquid crystals. It is proposed that such a transition is the explanation for recent neutron scattering results in MnSi. Predictions are made that will allow for experimental tests of this proposal.

Figure 1

Phase diagram of MnSi, including the proposed chiral liquid phase with an associated critical point (CP). The CP may be at $T<0$ and, thus, inaccessible. Second- (or very weakly first-) order transitions, first-order transitions, and crossovers are denoted by solid, dashed, and dotted lines, respectively. The non-Fermi-liquid (NFL) region includes the chiral liquid, and the chiral gas extends below $T^{*}$. The precise structure near the tricritical point (TCP) is not known. See the text for further information.