Related papers: Quantum order by disorder and accidental soft mode…
We investigate the effect of quenched bond-disorder on the anisotropic spin-1/2 (XXZ) chain as a model for disorder induced quantum phase transitions. We find non-universal behavior of the average correlation functions for weak disorder,…
A single crystal of the Co2+ based pyrochlore NaCaCo2F7 was studied by inelastic neutron scattering. This frustrated magnet with quenched exchange disorder remains in a strongly correlated paramagnetic state down to one 60th of the…
We study the effect in geometrically frustrated antiferromagnets of weak, random variations in the strength of exchange interactions. Without disorder the simplest classical models for these systems have macroscopically degenerate ground…
We consider the possibility that the discrete long-range ordered states of Er2Ti2O7 are selected energetically at the mean field level as an alternative scenario that suggests selection via thermal fluctuations. We show that nearest…
Spin-1/2 antiferromagnetic triangular lattice models are paradigms of geometrical frustration, revealing very different ground states and quantum effects depending on the nature of anisotropies in the model. Due to strong spin orbit…
We study the classical Heisenberg model for spins on a pyrochlore lattice interacting via long range dipole-dipole forces and nearest neighbor exchange. Antiferromagnetic exchange alone is known not to induce ordering in this system. We…
We present neutron diffraction analysis of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ over a wide temperature (10 to 300 K) and compositional ($0.11 \leq x \leq 0.79$) range, including the normal state, the magnetically ordered state, and the…
The glassy behavior observed in the pyrochlore magnet Y2Mo2O7, where the magnetic Mo^{4+} ions interact predominantly via isotropic nearest neighbor antiferromagnetic exchange, possibly with additional weak disorder, is a distinct class of…
We reconsider the random bond antiferromagnetic spin-1/2 chain for weak disorder and demonstrate the existence of crossover length scale x_W that diverges with decreasing strength of the disorder. Recent DMRG calculations [Phys. Rev. Lett.…
A theory of the anisotropic superexchange and low energy spin excitations in a Mott insulator with t_{2g} orbital degeneracy is presented. We observe that the spin-orbit coupling induces frustrating Ising-like anisotropy terms in the spin…
We systematically investigate the ground-state and the spectral properties of antiferromagnets on a kagom\'{e} lattice with several common types of the planar anisotropy: $XXZ$, single-ion, and out-of-plane Dzyaloshinskii-Moriya. Our main…
We report on diffuse neutron scattering experiments providing evidence for the presence of random strains in the quantum spin ice candidate Pr2Zr2O7. Since Pr is a non-Kramers ion, the strain deeply modifies the picture of Ising magnetic…
From a microscopic model for the pyrochlore antiferromagnet Tb2Sn2O7, including the crystal field Hamiltonian and interactions between the angular momenta, we compute an effective pseudospin-1/2 Hamiltonian Heff$ that incorporates…
The Heisenberg antiferromagnet on the kagome lattice is an archetypal instance of how large ground state degeneracies arise, and how they may get resolved by thermal and quantum fluctuations. Augmenting the Heisenberg model by chiral spin…
We consider a system of spins on the sites of a three-dimensional pyrochlore lattice of corner-sharing tetrahedra interacting with a predominant effective $xy$ exchange. In particular, we investigate the selection of a long-range ordered…
The effect of quantum and thermal fluctuations on the phase diagram of spin-2 BECs is examined. They are found to play an important role in the nematic part of the phase diagram, where a mean-field treatment of two-body interactions is…
We demonstrate the appearance of thermal order by disorder in Ising pyrochlores with staggered antiferromagnetic order frustrated by an applied magnetic field. We use a mean-field cluster variational method, a low-temperature expansion and…
The frustrated pyrochlore antiferromagnet Gd$_{2}$Ti$_{2}$O$_{7}$ has an unusual partially-ordered magnetic structure at the lowest measurable temperatures. This structure is currently believed to involve four magnetic propagation vectors…
We report inelastic neutron scattering measurements in the hidden order state of URu$_{2-x}$Re$_x$Si$_2$ with $x$ = 0.10. We observe that towards the ferromagnetic quantum critical point induced by the negative chemical pressure of…
We investigated the electronic and magnetic properties of the pyrochlore oxide Cd$_2$Os$_2$O$_7$ using the density-functional theory plus on-site repulsion ($U$) method, and depict the ground-state phase diagram with respect to $U$. We…