Transport signature of the magnetic Berezinskii-Kosterlitz-Thouless transition

Motivated by recent experimental progress in 2D magnetism, we theoretically study spin transport in 2D easy-plane magnets at finite temperatures across the Berezinskii-Kosterlitz-Thouless (BKT) phase transition, by developing a duality mapping to the 2+1D electromagnetism with the full account of spin’s finite lifetime. In particular, we find that the non-conservation of spin gives rise to a distinct signature across the BKT transition, with the spin current decaying with distance power-law (exponentially) below (above) the transition; this is detectable in the proposed experiment with NiPS_33 and CrCl_33.

Effects of Dzyaloshinsky-Moriya Interaction on Planar Rotator Model on Triangular Lattice

The thermodynamic properties and some critical properties of the planar rotator model with chiral Dzyaloshinsky-Moriya (DM) interaction on triangular lattice are analyzed using a hybrid Monte Carlo method. It has been shown that there is a XY-like Berezinskii-Kosterlitz-Thouless (BKT) phase transition in this model. The ground state of this spiral system and the effects of size mismatch are also discussed.

CONFORMALITY LOST

We consider zero-temperature transitions from conformal to non-conformal phases in quantum theories. We argue that there are three generic mechanisms for the loss of conformality: (i) fixed point goes to zero coupling, (ii) fixed point runs off to infinite coupling, or (iii) an IR fixed point annihilates with a UV fixed point and they both disappear into the complex plane. We give examples of the last case and show that the critical behavior of the mass gap is similar to that of the inverse correlation length in the finite temperature Berezinskii-Kosterlitz-Thouless (BKT) phase transition, ξ ~ exp (c/|T-Tc|1/2). We speculate that the chiral phase transition in QCD at large number of fermion flavors belongs to this universality class, and attempt to identify the UV fixed point that annihilates with the Banks-Zaks fixed point at the lower end of the conformal window.

HIGGS-INSPIRED CORRECTIONS TO THE RG FLOW IN THE FINITE-TEMPERATURE 3D GEORGI–GLASHOW MODEL AND ITS SU(N)-GENERALIZATION

The RG flow in the finite-temperature (2 + 1)D Georgi–Glashow model is explored in the regime when the Higgs field is not infinitely heavy, but its mass is rather of the same order of magnitude as the mass of the W-boson. The corrections to the standard RG flow are derived to the leading order in the inverse mass of the Higgs boson. The scaling of the free-energy density in the critical region and the value of the critical temperature of the Berezinsky–Kosterlitz–Thouless (BKT) phase transition are found to be unaffected by the finiteness of the Higgs–boson mass. The evolution of the Higgs mass itself is also investigated and shown to be rather weak, that enables one to treat this parameter as a constant. The same analysis is further performed in the SU (N)-case at N > 2, where the RG invariance is demonstrated to hold only approximately, in a certain sense. Modulo this approximation, the critical behavior of the SU (N)-model turns out to be identical to that of the SU(2)-one.

VORTICES ON THE STRING AND SUPERSTRING WORLD SHEETS

The world-sheet dynamics of the first quantized string propagating in nonsimply connected space is considered. Presence of the vortices on the world sheet leads to Berezinsky-Kosterlitz-Thouless (BKT) phase transition. Bosonic and superstring cases are discussed. It is shown that Hagedorn transition can be described as BKT transition both in bosonic and superstring cases.