It is known from the Mermin-Wagner theorem that magnetic long-range order can exist in two
dimensions only at zero temperature, but even then it can still be destroyed eg by quantum …

In combination with Laughlin's treatment of the quantized Hall conductivity, the Lieb-Schultz-
Mattis argument is extended to quantum many-particle systems (including quantum spin …

We report the results of magnetization and specific heat measurements on Ba 3 CoSb 2 O 9,
in which the magnetic Co 2+ ion has a fictitious spin 1/2, and provide evidence that a spin …

We have performed high-field magnetization and electronic spin resonance (ESR)
measurements on Ba 3 CoSb 2 O 9 single crystals, which approximates the two-dimensional …

Using mean-field theory, exact diagonalizations, and SU (3) flavor theory, we have precisely
mapped out the phase diagram of the S= 1 bilinear-biquadratic Heisenberg model on the …

The triangular lattice of S= 1/2 spins with XXZ anisotropy is a ubiquitous model for various
frustrated systems in different contexts. We determine the quantum phase diagram of the …

The magnetic phase transitions of Cs 2 CuBr 4, which may be described as a spin-1 2 quasi-
two-dimensional frustrated antiferromagnet, were investigated by means of magnetization …

Plateaus can be observed in the zero-temperature magnetization curve of quantum spin
systems at rational values of the magnetization. In one dimension, the appearance of a …

Magnetization processes of spin-1 2 Heisenberg ladders are studied using strong-coupling
expansions, numerical diagonalization of finite systems, and a bosonization approach. We …

Recent experimental and theoretical investigations of frustrated triangular-lattice
antiferromagnets are reviewed. An analysis is made of phases with different structures …