A self-consistent theory of phase transitions in noncollinear magnets

TL;DR

This paper develops a self-consistent theoretical framework to analyze phase transitions in noncollinear magnets, revealing second-order transitions in key physical cases and providing critical exponents.

Contribution

It introduces a self-consistent screening approximation for noncollinear magnets with a specific symmetry-breaking scheme, showing the nature of phase transitions and critical exponents.

Findings

Second-order phase transitions in N=2,3, D=3 cases.

No fluctuation-induced first-order transitions.

Critical exponents eta are 0.11 for N=3 and 0.15 for N=2.

Abstract

I study phase transitions occuring in noncollinear magnets by means of a self-consistent screening approximation. The Ginzburg-Landau theory involves two N-component vector fields with two independent quartic couplings allowing a symmetry-breaking scheme which is SO(N)times SO(2) broken down to SO(N-2)times SO(2)_diag. I find that there is a second-order phase transition in the physical cases N=2,3, D=3 and that there is no fluctuation-induced first-order transition. This is very similar to the case of the normal-to-superconducting phase transition as recently found by Radzihovsky. The exponents are eta(N=3,D=3)= 0.11, eta(N=2,D=3) =0.15 and go smoothly to the large-N limit.