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By applying pressure to the itinerant chiral magnet MnSi, a state
with non-Fermi liquid electrical transport and unusual partially
ordered magnetism has been observed. These experiments quite
intriguingly suggest diffuse spin correlations and slow dynamics in a
pure crystalline metal.
As a possible route towards a theory of the partially ordered state, we show that electrons interacting with a fluctuating magnetic background have a natural gauge theory description. We introduce new variables, where spin and charge of the conduction electrons appear separated. In this language, the helically ordered phase appears as a Anderson-Higgs phase where the gauge field is gapped and the low-energy helimagnon spectrum is obtained. It is currently not known whether this gauge theory also has (deconfined) disordered phases, which could account for the unusual behavior of MnSi under pressure. |
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