相关论文: Lattice instabilities in cubic pyrochlore Bi$_2$Ti…
Geometrical frustration among interacting spins combined with strong quantum fluctuations destabilize long-range magnetic order in favour of more exotic states such as spin liquids. By following this guiding principle, a number of spin…
We study the antiferrodistortive instability and its interaction with ferroelectricity in cubic perovskite compounds. Our first-principles calculations show that coexistence of both instabilities is very common. We develop a…
Pb_1.83Mg_0.29Nb_1.71O_6.39 (PMN) crystallizing in a cubic pyrochlore structure exhibits, as the first dielectrics with pyrochlore structure, typical feature of quantum paraelectrics - its permittivity continuously increases on cooling and…
The magnetic pyrochlore oxide materials of general chemical formula R2Ti2O7 and R2Sn2O7 (R = rare earth) display a host of interesting physical behaviours depending on the flavour of rare earth ion. These properties depend on the value of…
We present a computational study of the layered copper oxychloride [CuCl]LaNb(2)O(7) that has been recently proposed as a spin-1/2 frustrated square lattice compound. Our results evidence an orbitally degenerate ground state for the…
The competitions between ferroelectric and rotational instabilities in rhombohedral PZT near x = 0.5 are investigated using first principles density functional supercell calculations. As expected, we find a strong ferroelectric instability.…
The complex structure and magnetism of Pr$_{2-x}$Bi$_x$Ru$_2$O$_7$ was investigated by neutron scattering and EXAFS. Pr has an approximate doublet ground-state and the first excited state is a singlet. This overall crystal field level…
We report the observation of a linear magnetoresistance in single crystals and epitaxial thin films of the pyrochlore iridate Bi$_2$Ir$_2$O$_7$. The linear magnetoresistance is positive and isotropic at low temperatures, without any sign of…
In this work we present inelastic neutron scattering experiments which probe the single ion ground states of the rare earth pyrochlores $R_2$Ti$_2$O$_7$ ($R$ = Tb, Dy, Ho). Dy$_2$Ti$_2$O$_7$ and Ho$_2$Ti$_2$O$_7$ are dipolar spin ices, now…
It has been suggested that the metal-insulator transitions in a number of spinel materials with partially-filled t_2g d-orbitals can be explained as orbitally-driven Peierls instabilities. Motivated by these suggestions, we examine…
The very nature of the ground state of the pyrochlore compound Yb$_2$Ti$_2$O$_7$ is much debated, as experimental results demonstrate evidence for both a disordered or a long-range ordered ground state. Indeed, the delicate balance of…
The (three-dimensional) pyrochlore lattice antiferromagnet with Heisenberg spins of large spin length $S$ is a highly frustrated model with an macroscopic degeneracy of classical ground states. The zero-point energy of (harmonic order) spin…
In low-dimensional metallic systems, lattice distortion is usually coupled to a density-wave-like electronic instability due to Fermi surface nesting (FSN) and strong electron-phonon coupling. However, the ordering of other electronic…
Interplay of spin-orbit coupling and vibronic coupling on heavy $d^1$ site of cubic double perovskites is investigated by ab initio calculations. The stabilization energy of spin-orbital-lattice entangled states is found comparable to or…
Neutron inelastic scattering measurements of the polar TO phonon mode in the cubic relaxor Pb(Mg1/3Nb2/3)O3, at room temperature, reveal anomalous behavior similar to that recently observed in the Pb(Zn1/3Nb2/3)_{0.92}Ti_{0.08}O3 system in…
The Tb$_2$Ti$_2$O$_7$ pyrochlore magnetic material is attracting much attention for its {\em spin liquid} state, failing to develop long range order down to 50 mK despite a Curie-Weiss temperature $\theta_{\rm CW} \sim -14$ K. In this paper…
We report a thorough study of Y$_{0.7}$La$_{0.3}$VO$_3$ single crystals by measuring magnetic properties, specific heat, thermal conductivity, x-ray and neutron diffraction with the motivation of revealing the lattice response to the…
Partially-ordered magnets are distinct from both spin liquids and conventional ordered magnets because order and disorder coexist in the same magnetic phase. Here, we determine the nature of partial order in the canonical frustrated…
We report detailed measurements of the low temperature magnetic phase diagram of Er$_2$Ti$_2$O$_7$. Heat capacity and time-of-flight neutron scattering studies of single crystals, subject to magnetic fields applied along the…
Vacancy ordered halide perovskites have been extensively investigated as promising lead-free alternatives to halide perovskites for various opto-electronic applications. Among these Cs$_{2}$TiBr$_{6}$ has been reported as a stable absorber…