Spin- S Designer Hamiltonians and the Square Lattice S=1 Haldane Nematic

Nematic order in square lattice frustrated ferromagnets.

We present a new scenario for the breakdown of ferromagnetic order in a two-dimensional quantum magnet with competing ferromagnetic and antiferromagnetic interactions. In this, dynamical effects lead to the formation of two-magnon bound states, which undergo Bose-Einstein condensation, giving rise to bond-centered nematic order. This scenario is explored in some detail for an extended Heisenber...

Complexity of commuting Hamiltonians on a square lattice of qubits

We consider the computational complexity of Hamiltonians which are sums of commuting terms acting on plaquettes in a square lattice of qubits, and we show that deciding whether the ground state minimizes the energy of each local term individually is in the complexity class NP. That is, if the ground states has this property, this can be proven using a classical certificate which can be efficien...

Magnetic Properties in a Spin-1 Random Transverse Ising Model on Square Lattice

In this paper we investigate the effect of a random transverse field, distributed according to a trimodal distribution, on the phase diagram and magnetic properties of a two-dimensional lattice (square with z=4),  ferromagnetic Ising system consisting of magnetic atoms with spin-1. This study is done using the effectivefield theory (EFT) with correlations method. The equations are derived using...

Low-temperature series expansions for the square lattice Ising model with spin S > 1

We derive low-temperature series (in the variable u = exp[−βJ/S2]) for the spontaneous magnetization, susceptibility, and specific heat of the spin-S Ising model on the square lattice for S = 2 , 2, 2 , and 3. We determine the location of the physical critical point and non-physical singularities. The number of non-physical singularities closer to the origin than the physical critical point gro...

Spin transport in the square lattice vortex state of rotational