Related papers: Ionic Ordering in Thiospinel CuIr$_{2}$S$_{4}$
Neutron diffraction, polarized neutron transmission, and small angle neutron scattering have been used to investigate the crystal structure and nature of the magnetic order in a polycrystalline sample of RuSr2Eu1.2Ce0.8Cu2O10. The sample…
We report on a detailed single crystal x-ray diffraction study of the unconventional spin-Peierls compound TiOCl. The intermediate phase of TiOCl is characterized by an incommensurate modulation which is virtually identical to that recently…
Substitution of rare-earth ions for Ca in Bi2Sr2CaCu2O8+y is known to cause a metal-insulator transition. Using resonant photoemission we study how this chemical substitution affects the electronic structure of the material. For the partial…
We present x-ray, neutron scattering and heat capacity data that reveal a coupled first-order magnetic and structural phase transition of the metastable mixed-valence post-spinel compound Mn$_3$O$_4$ at 210 K. Powder neutron diffraction…
We report on the charge-ordered structure of LiRh2O4 arising below the metal-insulator transition at 170 K. Structural studies using synchrotron X-rays have revealed that the charge-ordered states of Rh3+ and Rh4+ with dimerization are…
We present a theory of the high-spin generalization of topological insulators and their doped superconducting states. The higher-spin topological insulators involve a pair of $J=3/2$ bands with opposite parity, and are characterized by…
We have synthesized and studied a new iridate, Ba13Ir6O30, with unusual Ir oxidation states: 2/3 Ir6+(5d3) ions and 1/3 Ir5+(5d4) ions. Its crystal structure features dimers of face-sharing IrO6 octahedra, and IrO6 monomers, that are linked…
We used femtosecond optical spectroscopy to study ultrafast spin and orbital ordering dynamics in the antiferromagnetic Mott insulator $\alpha$-Sr$_2$CrO$_4$. This chromate system possesses multiple spin and orbital ordered phases, and…
Sr2IrO4 is a magnetic insulator assisted by strong spin-orbit coupling (SOC) whereas the Sr2RuO4 is a p-wave superconductor. The contrasting ground states have been shown to result from the critical role of the strong SOC in the iridate.…
The possible existence of topological insulators in cubic pyrochlore iridates A$_{2}$Ir$_{2}$O$_{7}$ (A = Y or rare-earth elements) is investigated by taking into account the strong spin-orbit coupling and trigonal crystal field effect. It…
In frustrated spinel antiferromagnets, dilution with non-magnetic ions can be a powerful strategy for probing unconventional spin states or uncovering interesting phenomena. Here, we present X-ray, neutron scattering and thermodynamic…
We report structural studies of the spin-orbit Mott insulator family K$_x$Ir$_y$O$_2$, with triangular layers of edge-sharing IrO$_6$ octahedra bonded by potassium ions. The potassium content acts as a chemical tuning parameter to control…
$\mathrm{Cu_2IrO_3}$ is among the newest layered honeycomb iridates and a promising candidate to harbor a Kitaev quantum spin liquid state. Here, we investigate the pressure and temperature dependence of its structure through a combination…
The chromium spinels MgCr2O4 and ZnCr2O4 are prime examples of the highly frustrated pyrochlore lattice antiferromagnet. Experiment has carefully established that both materials, upon cooling, distort to lower symmetry and order…
Neutron diffraction measurements are presented exploring the magnetic and structural phase behaviors of the candidate J$_{eff}=1/2$ Mott insulating iridate Sr$_2$IrO$_4$. Comparisons are drawn between the correlated magnetism in this single…
Topological states of matter originate from distinct topological electronic structures of materials. As for strong topological insulators (STIs), the topological surface (interface) is a direct consequence of electronic structure transition…
Synchrotron X-ray diffraction experiment shows that the metal-insulator transition occurring in a ferromagnetic state of a hollandite K$_2$Cr$_8$O$_{16}$ is accompanied by a structural distortion from the tetragonal $I4/m$ to monoclinic…
We report on neutron diffraction, thermal expansion, magnetostriction, dielectric, and specific heat measurements on polycrystalline FeCr2S4 in external magnetic fields. The ferrimagnetic ordering temperatures $T_{\mathrm{C}}\approx 170$ K…
We report unusual effects of nonmagnetic impurities on the spin-triplet superconductor Sr2RuO4. The substitution of nonmagnetic Ti4+ for Ru4+ induces localized-moment magnetism characterized by unexpected Ising anisotropy with the easy axis…
Understanding of metal insulator transitions in a strongly correlated system, driven by Anderson localization (disorder) and/or Mott localization (correlation), is a long standing problem in condensed matter physics. The prevailing…