arXiv subjects

Krishanu Roychowdhury

Publications and source records attributed to Krishanu Roychowdhury.

21 records · Page 2Linked to original sources

arXiv2015

Z2 topological liquid of hard-core bosons on a kagome lattice at 1/3 filling

We consider hard-core bosons on the kagome lattice in the presence of short range repulsive interactions and focus particularly on the filling factor 1/3. In the strongly interacting limit, the low energy excitations can be described by the quantum fully packed loop coverings on the triangular lattice. Using a combination of tensor-product state based methods and exact diagonalization techniques, we show that the system has an extended Z2 topological liquid phase as well as a lattice nematic phase. The latter breaks lattice rotational symmetry. By tuning appropriate parameters in the model, we study the quantum phase transition between the topological and the symmetry broken phases. We construct the critical theory for this transition using a mapping to an Ising gauge theory that predicts the transition to belong to the O(3) universality class.

cond-mat.str-el↗

arXiv2014

Tensor renormalization group approach to classical dimer models

We analyze classical dimer models on the square and triangular lattice using a tensor network representation of the dimers. The correlation functions are numerically calculated using the recently developed "Tensor renormalization group" (TRG) technique. The partition function for the dimer problem can be calculated exactly by the Pfaffian method which is used here as a platform for comparing the numerical results. TRG turns out to be a powerful tool for describing gapped systems with exponentially decaying correlations very efficiently due to its fast convergence. This is the case for the dimer model on the triangular lattice. However, the convergence becomes very slow and unstable in case of the square lattice where the model has algebraically decaying correlations. We highlight these aspects with numerical simulations and critically appraise the robustness of TRG approach by contrasting the results for small and large system sizes against the exact calculations. Furthermore, we benchmark our TRG results with classical Monte Carlo (MC) method.

cond-mat.str-el↗

arXiv2014

Interplay of charge and spin fluctuations of strongly interacting electrons on the kagome lattice

We study electrons hopping on a kagome lattice at third filling described by an extended Hubbard Hamiltonian with on-site and nearest-neighbour repulsions in the strongly correlated limit. As a consequence of the commensurate filling and the large interactions, each triangle has precisely two electrons in the effective low energy description, and these electrons form chains of different lengths. The effective Hamiltonian includes the ring exchange around the hexagons as well as the nearest-neighbor Heisenberg interaction. Using large scale exact diagonalization, we find that the effective model exhibits two different phases: If the charge fluctuations are small, the magnetic fluctuations confine the charges to short loops around hexagons, yielding a gapped charge ordered phase. When the charge fluctuations dominate, the system undergoes a quantum phase transition to a resonating plaquette phase with ordered spins and gapless spin excitations. We find that a peculiar conservation law is fulfilled: the electron in the chains can be divided into two sublattices, and this division is conserved by the ring exchange term.

cond-mat.str-el↗