Showing papers by "Shivaji Lal Sondhi published in 2002"
TL;DR: The contribution of superconducting fluctuations to thermal transport in the normal state, at low magnetic fields is calculated in the Gaussian approximation to their critical dynamics which is also the Aslamazov-Larkin approximation in the microscopics.
Abstract: We calculate the contribution of superconducting fluctuations to thermal transport in the normal state, at low magnetic fields. We do so in the Gaussian approximation to their critical dynamics which is also the Aslamazov-Larkin approximation in the microscopics. Our results for the thermal conductivity tensor and the transverse thermoelectric response are new. The latter compare favorably with the data of Ong and collaborators on the Nernst effect in the cuprates.
163 citations
TL;DR: Landau theory is employed, extending an investigation begun by Yamashita and Ueda for the case of S = 1, and classical analyses are used to argue that magnetoelastic couplings generate bond order via a spin-Peierls transition.
Abstract: We study the effects of magnetoelastic couplings on pyrochlore antiferromagnets. We employ Landau theory, extending an investigation begun by Yamashita and Ueda for the case of S = 1, and classical analyses to argue that such couplings generate bond order via a spin-Peierls transition. This is followed by, or concurrent with, a transition into one of several possible low-temperature Neel phases, with most simply collinear, but also coplanar or mixed spin patterns. In a collinear Neel phase, a dispersionless stringlike magnon mode dominates the resulting excitation spectrum, providing a distinctive signature of the parent geometrically frustrated state. We comment on the experimental situation.
154 citations
TL;DR: In this article, the authors study the hard core dimer model on the triangular lattice and show that the model is deconfining: the monomer-monomer correlator falls off exponentially to a constant value $0.1494\dots{},$ only slightly below the nearest-neighbor value of $1/6.$.
Abstract: We study the classical hard-core dimer model on the triangular lattice. Following Kasteleyn's fundamental theorem on planar graphs, this problem is soluble using Pfaffians. This model is particularly interesting for, unlike the dimer problems on the bipartite square and hexagonal lattices, its correlations are short ranged with a correlation length of less than one lattice constant. We compute the dimer-dimer and monomer-monomer correlators, and find that the model is deconfining: the monomer-monomer correlator falls off exponentially to a constant value $0.1494\dots{},$ only slightly below the nearest-neighbor value of $1/6.$ We also consider the anisotropic triangular lattice model in which the square lattice is perturbed by diagonal bonds of one orientation and small fugacity. We show that the model becomes noncritical immediately and that this perturbation is equivalent to adding a mass term to each of two Majorana fermions that are present in the long wavelength limit of the square lattice problem.
113 citations
TL;DR: In this paper, it was shown that the tetrahedral molecule at the heart of the pyrochlore magnet undergoes a Jahn-Teller distortion when lattice motion is coupled to the antiferromagnetism.
Abstract: In the highly frustrated pyrochlore magnet spins form a lattice of corner-sharing tetrahedra. We show that the tetrahedral ``molecule'' at the heart of this structure undergoes a Jahn-Teller distortion when lattice motion is coupled to the antiferromagnetism. We extend this analysis to the full pyrochlore lattice by means of Landau theory and argue that it should exhibit ``spin-Peierls'' phases with bond order but no spin order. We find a range of N\'eel phases, with collinear, coplanar, and noncoplanar order. While collinear N\'eel phases are easiest to generate microscopically, we also exhibit an interaction that gives rise to a coplanar state instead.
93 citations