The properties of transition metal compounds are largely determined by nontrivial interplay
of different degrees of freedom: charge, spin, lattice, and also orbital ones. Especially rich …

We review the interplay of frustration and strong electronic correlations in quasi-two-
dimensional organic charge transfer salts, such as (BEDT-TTF) 2 X and Et n Me 4− n Pn [Pd …

An overview of one-and two-dimensional quantum spin systems based on transition-metal
oxides and halides of current interest is given, such as spin-Peierls, spin-dimer …

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 …

We consider quantum spin systems with dimerization, which at strong coupling have singlet
ground states. To account for strong correlations, the S= 1 elementary excitations are …

We determine the phase diagram of a generalized Shastry-Sutherland model, using a
combination of dimer-and quadrumer-boson methods and numerical exact diagonalization …

We show that in transition-metal compounds containing structural metal dimers there may
exist in the presence of different orbitals a special state with partial formation of singlets by …

We have performed ab initio calculations of exchange couplings in the layered vanadates
CaV 2 O 5, MgV 2 O 5, CaV 3 O 7, and CaV 4 O 9. The uniform susceptibility of the …

Using a spin-only model, we compute spin excitation spectra in a bond-centered stripe state
with long-range magnetic order. We employ a bond operator formalism, which naturally …

We study the phase diagram of two models of spin-1∕ 2 antiferromagnets composed of
corner-sharing tetrahedra, the basis of the pyrochlore structure. Primarily, we focus on the …