Alladi Ramakrishnan Hall

Melting of three-sublattice order in easy-axis antiferromagnets on triangular and kagome lattices

Kedar Damle

TIFR, Mumbai

Triangular and Kagome lattice antiferromagnets in which the spins are preferentially oriented along a fixed ``easy-axis'' often order at low temperature in a pattern that
distinguishes the three sublattices of the underlying triangular Bravais lattice. This ``three-sublattice order'' melts
in zero field {\em either} via a ``two-step melting'' transition, with an intermediate-temperature phase characterized by power-law three-sublattice order controlled by a temperature dependent power-law exponent $\eta(T) \in (\frac{1}{9},\frac{1}{4})$,
{\em or} via a transition described by the three-state Potts model. Here, we predict that the uniform susceptibility to a small field $B$ along the easy-axis diverges
as $\chi(B) \sim |B|^{-\frac{4 - 18 \eta}{4-9\eta}}$ in a large part of the intermediate power-law ordered phase (corresponding to $\eta(T) \in (\frac{1}{9},\frac{2}{9})$), providing a thermodynamic signature of two-step melting.
[collaborators: Dariush Heidarian, Geet Ghanshyam, Sounak Biswas]