Quantum PhaseTransitions and Exotic Phases in Metallic Helimagnets

I will review some of the current theoretical understanding of the exotic properties of chiral magnets, in particular the metallic helimagnet MnSi. In the ordered phase, a helical Goldstone mode leads to corrections to Fermi-liquid behavior, and to a non-Fermi liquid single-particle relaxation rate [1]. On the phase boundary, a tricritical point pushes the quantum critical point to a nonzero external magnetic field, where the quantum critical behavior has been determined exactly [2]. In the disordered phase, an analogy with chiral liquid crystals suggests a first-order transition from a chiral liquid to a chiral gas as an explanation for neutron scattering data [3]. The observed non-Fermi-liquid transport behavior in the disordered phase [4] remains an open problem. \medskip\par\noindent [1] D. Belitz, T.R. Kirkpatrick, and A. Rosch, Phys. Rev. B {\bf 73}, 054431 (2006); Phys. Rev. B {\bf 74}, 024409 (2006). \smallskip\par\noindent [2] D. Belitz, T.R. Kirkpatrick, and J. Rollb{\"u}hler, Phys. Rev. Lett. {\bf 94}, 027205 (2005). \smallskip\par\noindent [3] S. Tewari, D. Belitz, and T.R. Kirkpatrick, Phys. Rev. Lett. {\bf 96}, 047207 (2006). \smallskip\par\noindent [4] C. Pfleiderer, S.R. Julian, and G.G. Lonzarich, Nature {\bf 414}, 427 (2004).