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We observe, with angle-resolved photoemission, a dramatic change in the electronic structure of two C60 monolayers, deposited respectively on Ag (111) and (100) substrates, and similarly doped with potassium to half-filling of the C60…
We investigate the possibility of doping C60 crystals by applying a strong electric field. For an accurate description of a C60 field-effect device we introduce a multipole expansion of the field, the response of the C60 molecules, and the…
Detailed measurements of the magnetic and transport properties of the two La1-xCaxMnO3 (x = 0.18, x = 0.20) single crystals straddling the compositional metal-insulator transition boundary (0.18 < xc < 0.22) are summarized. The analysis of…
The role of orbital ordering on metal-insulator transition of transition-metal oxides is investigated by the cluster self-consistent field approach in the strong correlation regime. A clear dependence of the insulating gap on the orbital…
Few-layered potassium nickel and cobalt oxides show drastic differences in catalytic activity based on metal ion preorganization. Uniform compositions $[(\mathrm{CoO}_2/\mathrm{K})_6$ or $(\mathrm{NiO}_2/\mathrm{K})_6]$ show limited…
Combining macroscopic and diffraction methods we have studied the electric, magnetic and struc- tural properties of RE_(1-x)Ca_xTiO_3 (RE=Y, Er, Lu) focusing on the concentration range near the metal-insulator transition. The insulating…
Thin films provide a versatile platform to tune electron correlations and explore new physics in strongly correlated materials. Epitaxially grown thin films of the alkali-doped fulleride K$_{3+x}$C$_{60}$, for example, exhibit %various…
For the past decades, the low-temperature phase of Ca$_3$Ru$_2$O$_7$ below the 48K first-order phase transition remains a puzzle with controversial suggestions involving metallic ferroelectric, orbital or magnetic ordering. Through analysis…
Within dynamical mean-field theory, we study the metal-insulator transition of a twofold orbitally degenerate Hubbard model as a function of a splitting \Delta of the degeneracy. The phase diagram in the U-\Delta plane exhibits two-band and…
We study the origin of the cubic to tetragonal and tetragonal to monoclinic structural transitions in KCrF3, and the associated change in orbital order, paying particular attention to the relevance of super-exchange in both phases. We show…
An orbital ordering, often observed in Mott insulators with orbital degeneracy, is usually supposed to disappear with doping, e.g. in the ferromagnetic metallic phase of manganites. We propose that the orbital ordering of a novel type may…
The application of modern layer-by-layer growth techniques to transition-metal oxide materials raises the possibility of creating new classes of materials with rationally designed correlated electron properties. An important step toward…
The spin-chain compounds, Ca3CuIrO6 and Ca3CuRhO6, crystallizing in a K4CdCl6-derived monoclinic structure, are investigated by ac and dc magnetization, isothermal remnant magnetization as well as heat capacity measurements. The results…
Oxides with $4d$/$5d$ transition metal ions are physically interesting for their particular crystalline structures as well as the spin-orbit coupled electronic structures. Recent experiments revealed a series of $4d$/$5d$ transition metal…
The primordial ingredient of cuprate superconductivity is the CuO2 unit cell. Here, theoretical attention usually concentrates on the intra-atom Coulombic interactions dominating the 3d^9 and 3d^10 configurations of each copper ion.…
Recently low-temperature structural transition has been reported for complex cubic compounds Cd6M (M=Ca, Yb, Y, rare earth) and it is believed that the transition is due to orientational ordering of an atomic shell in the icosahedral…
We show that Rb_4C_60 transforms from its ambient pressure orientationally disordered tetragonal structure to an ordered orthorhombic structure (isostructural to Cs_4C_60) at or above 0.4 GPa. This opens the possibility of studying the…
Based on a simple model for ordering of hexagons on square planar lattice, an attempt has been made to consider possible structure of C(_{60}) fullerite in its low temperature phase. It is shown that hexagons, imitating fullerens oriented…
A series of CaxCoO2 (0.15 <= x <= 0.40) materials have been prepared by means of ion exchange reaction from NaxCoO2. Transmission electron microscopy (TEM) measurements revealed a rich variety of structural phenomena resulting from cation…
Motivated by the recent experimental report of a possible light-induced superconductivity in A3C60 at high temperature [Mitrano et al., Nature 530, 451 (2016)], we investigate theoretical mechanisms for enhanced superconductivity in A3C60…