These lecture notes introduce quantum spin systems and several computational methods for
studying their ground‐state and finite‐temperature properties. Symmetry‐breaking and …

We study the spin-1/2 Heisenberg model on the square lattice with first-and second-
neighbor antiferromagnetic interactions J 1 and J 2, which possesses a nonmagnetic region …

The nature of the zero-temperature phase diagram of the spin-1/2 J 1-J 2 Heisenberg model
on a square lattice has been debated in the past three decades, and it remains one of the …

We present numerical exact results for the ground state and the low-lying excitations for the
spin-1/2 J 1-J 2 Heisenberg antiferromagnet on finite square lattices of up to N= 40 sites …

We study the ground-state properties of the two-dimensional spin-1/2 J 1-J 2 Heisenberg
model on a square lattice, within diagrammatic approximations using an auxiliary-fermion …

We describe correlator product states, a class of numerically efficient many-body wave
functions to describe strongly correlated wave functions in any dimension. Correlator …

We propose a new ansatz for the ground-state wave function of quantum many-body
systems on a lattice. The key idea is to cover the lattice with plaquettes and obtain a state …

Crystal structure, electronic structure, and magnetic behavior of the spin-1 2 quantum
magnet Na 1.5 VOPO 4 F 0.5 are reported. The disorder of Na atoms leads to a sequence of …

We use the spin functional renormalization group to investigate the J 1-J 2 quantum
Heisenberg model on a square lattice. By incorporating sum rules associated with the fixed …

We introduce S z spin-projection based on cluster mean-field theory and apply it to the
ground state of strongly correlated spin systems. In cluster mean-fields, the ground state …