We review results concerning the critical behavior of spin systems at equilibrium. We
consider the Ising and the general O (N)-symmetric universality classes, including the N→ 0 …

Recent realizations of intrinsic, long-range magnetic orders in two-dimensional (2D) van der
Waals materials have ignited tremendous research interest. In this work, we employ the XXZ …

Abstract The Mermin-Wagner theorem states that long-range magnetic order does not exist
in one-(1D) or two-dimensional (2D) isotropic magnets with short-ranged interactions. Here …

The remarkable and fascinating properties of two-dimensional (2D) materials have raised
them to the rank of most promising candidates for technological applications. In particular …

We prove that various SO (n)-invariant n-vector models with interactions which have a deep
and narrow enough minimum have a first-order transition in the temperature. The result …

Recently, a colossal magnetoresistance (CMR) was observed in Eu Cd 2 P 2, a compound
that does not fit the conventional mixed-valence paradigm. Instead, experimental evidence …

Motivated by the physical properties of vesignieite BaCu 3 V 2 O 8 (OH) 2, we study the J 1−
J 3 Heisenberg model on the kagome lattice, which is proposed to describe this compound …

Liquid crystals in two dimensions undergo a first-order isotropic-to-quasi-nematic transition,
provided the particle interactions are sufficiently “sharp and narrow.” This implies phase …

We investigate the low-temperature behavior of two-dimensional (2D) RP N-1 models,
characterized by a global O (N) symmetry and a local Z 2 symmetry. For N= 3 we perform …

At low temperatures, the two-dimensional continuous-spin systems exhibit large correlation
lengths. Some of them show the Berezinskii–Kosterlitz–Thouless-like transitions, and some …