Title
"Quantum hard-square models: from the exact ground state to entanglement spectra"
Hosho Katsura (Gakushuin Univeristy)
Abstract
We introduce and study a class of quantum lattice-gas models for which the exact ground state can be expressed as a superposition of states, each of which is characterized by a particle configuration with nearest-neighbor exclusion. The model can be defined on any lattice in any dimension. We show that the ground state is unique and there is an energy gap when the parameter $z$ corresponding to the fugacity is sufficiently small. In one dimension, explicit expressions for a couple of excited states including the first excited one can be obtained. For the model on two-leg ladders, we study the entanglement spectra numerically and find that the entanglement Hamiltonians are well described by $c<1$ minimal conformal field theories. We also show that the entanglement Hamiltonian for the triangular ladder is integrable despite the fact that the original quantum lattice-gas model is nonintegrable.
[1] S. Tanaka, R. Tamura, and H. Katsura, Phys. Rev. A 86, 032326 (2012).
[2] I. Lesanovsky and H. Katsura, Phys. Rev. A 86, 041601(R) (2012).
