The transverse field Ising and XY models (the simplest quantum spin models) provide the
organising principle for the rich variety of interconnected subjects which are covered in this …

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

Recent theoretical and experimental work suggests that the honeycomb cobaltates, initially
proposed as candidate Kitaev quantum magnets, are in fact described by a pseudospin-1/2 …

We present a detailed study in the paramagnetic regime of the frustrated s= 1/2 spin-
compound linarite PbCuSO 4 (OH) 2 with competing ferromagnetic nearest-neighbor and …

Various lattice geometries and boundary conditions are used to investigate valence-bond-
solid (VBS) ordering in the ground state of an S= 1/2 square-lattice quantum spin model …

Abstract The spin-1/2 chain with isotropic exchange J 1, J 2> 0 between first and second
neighbors is frustrated for either sign of J 1 and has a singlet ground state (GS) for J 1/J 2⩾ …

The J 1-J 2 spin-chain model with nearest-neighbor J 1 and next-nearest-neighbor
antiferromagnetic J 2 interaction is one of the most popular frustrated magnetic models. This …

We review quantum phase transitions of spin systems in transverse magnetic fields taking
the examples of the spin-1/2 Ising and XY models in a transverse field. Beginning with an …

The phase diagram of an antiferromagnetic ladder with frustrating next-nearest-neighbor
couplings along the legs is determined using numerical methods (exact diagonalization and …

Abstract The spin-1/2 chain with isotropic Heisenberg exchange J 1, J 2> 0 between first and
second neighbors is frustrated for either sign of J 1. Its quantum phase diagram has critical …