Related papers: Vector-spin-chirality order in a dimerized frustra…
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 J1. Its quantum phase diagram has critical points at fixed $J_1/J_2$ between gapless phases with…
Field-dependent specific heat and neutron scattering measurements were used to explore the antiferromagnetic S=1/2 chain compound CuCl2 * 2((CD3)2SO). At zero field the system acquires magnetic long-range order below TN=0.93K with an…
In this study, a spin-1/2 extended anisotropic XY chain has been introduced in which both time reversal and SU(2) symmetries are broken but $Z_2$ symmetry is preserved. Magnetic and topological phase diagrams in the parameter space have…
We study the ground-state phase diagram of a one-dimensional spin-1/2 easy-plane XXZ model with a ferromagnetic nearest-neighbor (NN) coupling $J_1$ and a competing next-nearest-neighbor (NNN) antiferromagnetic coupling $J_2$ in the…
Vector-chiral (VC) antiferromagnetism is a spiral-like ordering of spins which may allow ferroelectricity to occur due to loss of space inversion symmetry. In this paper we report direct experimental observation of ferroelectricity in the…
The ordering temperature of a quasi-one-dimensional system, consisting of weakly interacting quantum spin-1/2 chains with antiferromagnetic spin-frustrating couplings (or zig-zag ladder) is calculated. The results show that a quantum…
We study spin-$1/2$ chains with long-range power-law decaying unfrustrated (bipartite) Heisenberg exchange $J_r \propto r^{-\alpha}$ and multi-spin interactions $Q$ favoring a valence-bond solid (VBS) ground state. Employing quantum Monte…
The $J_1-J_2$ spin chain model with nearest neighbor $J_1$ and next nearest neighbor anti-ferromagnetic $J_2$ interaction is one of the most popular frustrated magnetic models. This model system has been extensively studied theoretically…
With decreasing temperature Sr$_2$VO$_4$ undergoes two structural phase transitions, tetragonal-to-orthorhombic-to-tetragonal, without long-range magnetic order. Recent experiments suggest, that only at very low temperature Sr$_{2}$VO$_{4}$…
Spin ladders are key models that act as intermediaries between one-dimensional and two-dimensional spin systems. In this study, we examine a coupled spin-$1/2$ ladder, where frustrated ladders with leg, rung, and diagonal interactions are…
We present our theoretical results on the mechanism of two transitions in vanadium spinel oxides $A$V$_2$O$_4$ ($A$=Zn, Mg, or Cd) in which magnetic V cations constitute a geometrically-frustrated pyrochlore structure. We have derived an…
Using the coupled cluster method we study the phase diagram of the spin-1/2 Heisenberg antiferromagnet on a honeycomb lattice with nearest-neighbor exchange coupling $J_{1}>0$ and frustrating next-nearest-neighbor coupling $J_{2} \equiv…
We investigate the competition between different orders in the two-leg spin ladder with a ring-exchange interaction by means of a bosonic approach. The latter is defined in terms of spin-1 hardcore bosons which treat the N\'eel and vector…
The magnetic behaviors of a spin-1/2 alternating Heisenberg antiferromagnetic chain in a staggered transverse magnetic field is studied by means of the density-matrix renormalization group method and Jordan-Wigner transformation. Quantum…
A class of exact spin ground states with nonzero averages of vector spin chirality, $<\v{S}_i \times \v{S}_j \cdot \hat{z}>$, is presented. It is obtained by applying non-uniform O(2) rotations of spin operators in the XY plane on the…
The quantum phases of one-dimensional spin $s= 1/2$ chains are discussed for models with two parameters, frustrating exchange $g = J_2 > 0$ between second neighbors and normalized nonfrustrating power-law exchange with exponent $\alpha$ and…
A ferrimagnetic spin model composed of $S=1/2$ spin-dimers and $S=5/2$ spin-chains is studied by combining the bond-operator representation (for $S=1/2$ spin-dimers) and Holstein-Primakoff transformation (for $S=5/2$ spins). A finite…
The spin-1/2 chain with isotropic exchange J1, J2 > 0 between first and second neighbors is frustrated for either sign of J1 and has a singlet ground state (GS) for J1/J2 $\ge - 4$. Its rich quantum phase diagram supports gapless, gapped,…
We study spin-half and spin-one Heisenberg models in the limit where one dimensional (1-D) linear chains, with exchange constant J1, are weakly coupled in an anisotropic triangular lattice geometry. Results are obtained by means of…
We study Heisenberg spin-1/2 and spin-1 chains with alternating ferromagnetic ($J_1^F$) and antiferromagnetic ($J_1^A$) nearest-neighbor interactions and a ferromagnetic next-nearest-neighbor interaction ($J_2^F$). In this model frustration…