Ament, L. J. P., Khaliullin, G.
We present a theory for Raman scattering and Resonant Inelastic X-ray Scattering (RIXS) in the low temperature ferromagnetic phase of YTiO$_3$ and compare this to the available experimental data. For...
Momentum dependence of orbital excitations in Mott-insulating titanates (2009)
Ulrich, C., Ament, L. J. P., Ghiringhelli, G., Braicovich, L., Sala, M. Moretti, Pezzotta, N., ...
High-resolution resonant inelastic x-ray scattering has been used to determine the momentum dependence of orbital excitations in Mott-insulating LaTiO$_3$ and YTiO$_3$ over a wide range of the...
Low-energy Mott-Hubbard excitations in LaMnO_3 probed by optical ellipsometry (2009)
Kovaleva, N. N., Oles, Andrzej M., Balbashov, A. M., Maljuk, A., Argyriou, D. N., Khaliullin, G., ...
We present a comprehensive ellipsometric study of an untwinned, nearly stoichiometric LaMnO_3 crystal in the spectral range 1.2-6.0 eV at temperatures 20 K < T < 300 K. The complex dielectric...
Low-energy Mott-Hubbard excitations in LaMnO$_3$ (2009)
Kovaleva, N. N., Oles, Andrzej M., Balbashov, A. M., Maljuk, A., Argyriou, D. N., Khaliullin, G., ...
More discussion from the theory is suggested
We study the magnetic interactions in Mott-Hubbard systems with partially filled $t_{2g}$-levels and with strong spin-orbit coupling. The latter entangles the spin and orbital spaces, and leads to a...
Turning a nickelate Fermi surface into a cuprate-like one through heterostructuring (2008)
Hansmann, P., Yang, Xiaoping, Toschi, A., Khaliullin, G., Andersen, O. K., Held, K.
Using the local density approximation and its combination with dynamical mean field theory, we show that electronic correlations induce a single sheet cuprate-like Fermi surface for LaNiO3/LaAlO3...
Unusual electron correlations in NaxCoO2 due to the spin-state quasidegeneracy of cobalt ions (2008)
Recent studies exposed many remarkable properties of layered cobaltates NaxCoO2. Surprisingly, many-body effects have been found to increase at sodium-rich compositions of NaxCoO2 where one expects a...
Origin of spatial variation of pairing gap in Bi-based high-Tc cuprates (2008)
Mori, M., Khaliullin, G., Tohyama, T., Maekawa, S.
Recently, scanning tunneling microscopy on Bi-2212 cuprate superconductor has revealed a spatial variation of the energy gap that is directly correlated with a modulation of the apical oxygen...
Spin, Orbital and Charge Order at the Interface between Correlated Oxides (2008)
The collective behavior of correlated electrons in the VO$_2-$interface layer of LaVO$_3$/SrTiO$_3$ heterostructure is studied within a quarter-filled $t_{2g}$-orbital Hubbard model on a square...
Grafe, H.J., Hammerath, F., Vyalikh, A., Urbanik, G., Kataev, V., Wolf, Th., ...
Physical Review B, 77(2008) S.014522/1-5
Muon-spin rotation study of magnetism in NaxCoO₂ single crystals with 0.78 ≼ x ≼ 0.97 (2007)
Bernhard, Christian, Niedermayer, Ch., Drew, Alan, Khaliullin, G., Bayrakci, S., Strempfer, J., ...
By muon spin rotation we investigated the magnetic properties of a series of highly Na-doped NaxCoO₂ single crystals with 0.78(1) ≼ x ≼ 0.97(1). Our data provide evidence for an intrinsically...
Muon-spin rotation study of magnetism in NaxCoO₂ single crystals with 0.78 ≼ x ≼ 0.97 (2007)
Bernhard, Christian, Niedermayer, Ch., Drew, Alan, Khaliullin, G., Bayrakci, S., Strempfer, J., ...
By muon spin rotation we investigated the magnetic properties of a series of highly Na-doped NaxCoO₂ single crystals with 0.78(1) ≼ x ≼ 0.97(1). Our data provide evidence for an intrinsically...
Spin polaron theory for the photoemission spectra of layered cobaltates (2007)
Recently, strong reduction of the quasiparticle peaks and pronounced incoherent structures have been observed in the photoemission spectra of layered cobaltates. Surprisingly, these many-body effects...
The origin of strong correlations and superconductivity in Na$_x$CoO$_2$ (2007)
We propose a minimal model resolving a puzzle of enigmatic correlations observed in sodium-rich Na$_x$CoO$_2$ where one expects a simple, free motion of the dilute $S=1/2$ holes doped into a band...
Cu NQR Wipeout Effect versus Charge Pseudogap in Zn/Ni Doped NdBa$_{2}$Cu$_{3}$O$_{6+y}$ (2007)
Hammerath, F., Vyalikh, A., Urbanik, G., Kataev, V., Wolf, Th., ...
We report $^{63,65}$Cu NQR measurements on slightly underdoped NdBa$_{2}$Cu$_{3}$O$_{6+y}$ single crystals heavily doped by Ni and Zn impurities. Owing to the impurity doping superconductivity is...
Doping induced magnetic clusters and Co spin state transition in Na_xCoO_2 with 0.78 (2007)
Bernhard, C., Niedermayer, Ch., Drew, A., Khaliullin, G., Bayrakci, S., Strempfer, J., ...
By muon spin rotation we investigated the magnetic properties of a series of highly Na doped NaxCoO2 single crystals with 0.78(1)
Magnetic properties of spin-orbital polarons in lightly doped cobaltates (2006)
Daghofer, M., Horsch, P., Khaliullin, G.
We present a numerical treatment of a spin-orbital polaron model for Na_xCoO_2 at small hole concentration (0.7 < x < 1). We demonstrate how the polarons account for the peculiar magnetic properties...
Charge susceptibility in the t-J model (2006)
Aristov, D. N., Khaliullin, G.
Momentum and doping dependence of the static charge susceptibility \chi(q) in the t-t'-J model is investigated. Correlations lead to a strongly momentum dependent renormalization of \chi(q). The...
Microscopic theory of magnetic interactions in KCuF3 and LaMnO3 – The role of charge transfer (2006)
Oleś, A. M., Feiner, L. F., Horsch, P., Khaliullin, G.
We analyze the spin exchange interactions J(ab) and J(c) in the A-type anti ferromagnetic phase of KCuF3 and LaMnO3. One finds that the quasi one-dimensional spin interactions in KCuF3 are consistent...
Spin-orbital entanglement and violation of the Goodenough-Kanamori rules (2006)
Oleś, A. M., Horsch, P., Feiner, L. F., Khaliullin, G.
We point out that large composite spin-orbital fluctuations in Mott insulators with t(2g) orbital degeneracy are a manifestation of quantum entanglement of spin and orbital variables. This results in...
Magnetism at the interface between ferromagnetic and superconducting oxides (2006)
Chakhalian, J., Freeland, J. W., Srajer, G., Strempfer, J., Khaliullin, G., Cezar, J. C., ...
Raman scattering in the Mott insulators LaTiO3 and YTiO3: Evidence for orbital excitations (2006)
Ulrich, C., Gössling, A., Grüninger, M., Guennou, M., Roth, H., Cwik, M., ...
Raman scattering is used to observe pronounced electronic excitations around 230 meV-well above the two-phonon range-in the Mott insulators LaTiO3 and YTiO3. Based on the temperature, polarization,...
Magnetism at the interface between ferromagnetic and superconducting oxides (2006)
Chakhalian, J, Freeland, JW, Srajer, G, Strempfer, J, Khaliullin, G, Cezar, JC, ...
Theory of orbital state and spin interactions in ferromagnetic titanates (2005)
A spin-orbital superexchange Hamiltonian in a Mott insulator with $t_{2g}$ orbital degeneracy is investigated. More specifically, we focus on a spin ferromagnetic state of the model and study a...
Low energy electronic states and triplet pairing in layered cobaltates (2005)
Khaliullin, G., Koshibae, W., Maekawa, S.
The structure of the low-energy electronic states in layered cobaltates is considered starting from the Mott insulating limit. We argue that the coherent part of the wave-functions and the...
Orbital excitations in titanates (2005)
Ulrich, C., Gössling, A., Grüninger, M., Guennou, M., Roth, H., Cwik, M., ...
Raman scattering is used to observe pronounced electronic excitations around 230 meV - well above the two-phonon range - in the Mott insulators LaTiO$_3$ and YTiO$_3$. Based on the temperature,...
Spin-controlled Mott-Hubbard bands in LaMnO_3 probed by optical ellipsometry (2004)
Kovaleva, N. N., Boris, A. V., Bernhard, C., Kulakov, A., Pimenov, A., Balbashov, A. M., ...
Spectral ellipsometry has been used to determine the dielectric function of an untwinned crystal of LaMnO_3 in the spectral range 0.5-5.6 eV at temperatures 50 K < T < 300 K. A pronounced...
Charge ordering and magneto-polarons in Na$_{0.82}$CoO$_2$ (2004)
Bernhard, C., Boris, A. V., Kovaleva, N. N., Khaliullin, G., Pimenov, A., Yu, L., ...
Using spectral ellipsometry, we have measured the dielectric function of a Na$_{0.82(2)}$CoO$_2$ crystal that exhibits bulk antiferromagnetism with T$_{N}$=19.8 K. We identify two prominent...
Miyashita, S., Kawaguchi, A., Kawakami, N., Khaliullin, G.
We investigate ground-state properties and quantum phase transitions in the one-dimensional S=1 spin-orbital model relevant to cubic vanadates. Using the density-matrix renormalization group, we...
Spin and orbital correlations in spin orbital models for t2g orbitals (2004)
Oleś, A. M., Horsch, P., Khaliullin, G.
We use exact diagonalization of four-site chains to demonstrate the effects of Hund's exchange and spin-orbit coupling on the intersite spin and orbital correlations in t(2g) systems. Except for...
Magnon softening and damping in the ferromagnetic manganites due to orbital correlations (2004)
Krivenko, S., Yaresko, A., Khaliullin, G., Fehske, H.
We present a theory for spin excitations in ferromagnetic metallic manganites and demonstrate that orbital fluctuations have strong effects on the magnon dynamics in the case these compounds are...
Charge Ordering and Magnetopolarons in Na0.82CoO2 (2004)
Bernhard, C., Boris, A. V., Kovaleva, N. N., Khaliullin, G., Pimenov, A., Yu, L., ...
Spin-Controlled Mott-Hubbard Bands in LaMnO3 Probed by Optical Ellipsometry (2004)
Kovaleva, N. N., Boris, A. V., Bernhard, C., Kulakov, A., Pimenov, A., Balbashov, A. M., ...
Physics of Transition Metal Oxides (2004)
Maekawa, S., Tohyama, T., Barnes, S. E., Ishihara, S., Koshibae, W., Khaliullin, G.
Charge dynamics of t-J model and anomalous bond-stretching phonons in cuprates (2003)
The density response of a doped Mott-Hubbard insulator is discussed starting from the t-J model in a slave boson 1/N representation. In leading order O(1) the density fluctuation spectra $N({\bf...
Magnetic Neutron Scattering Study of YVO3: Evidence for an Orbital Peierls State (2003)
Ulrich, C., Khaliullin, G., Sirker, J., Reehuis, M., Ohl, M., Miyasaka, S., ...
Magnetic neutron scattering study of YVO3: evidence for an orbital Peierls state (2003)
Ulrich, C., Khaliullin, G., Sirker, J., Reehuis, M., Ohl, M., Miyasaka, S., ...
This version is available at the following Publisher URL: http://prl.aps.org
Entropy Driven Dimerization in a One-Dimensional Spin-Orbital Model (2002)
We study a new version of the one-dimensional spin-orbital model with spins S=1 relevant to cubic vanadates. At small Hund's coupling J_H we discover dimerization in a pure electronic system solely...
Magnetic neutron scattering study of YVO3: Evidence for an orbital Peierls state (2002)
Ulrich, C., Khaliullin, G., Sirker, J., Reehuis, M., Ohl, M., Miyasaka, S., ...
Neutron spectroscopy has revealed a highly unusual magnetic structure and dynamics in YVO$_3$, an insulating pseudocubic perovskite that undergoes a series of temperature induced phase transitions...
Magnetic Order and Dynamics in an Orbitally Degenerate Ferromagnetic Insulator (2002)
Ulrich, C., Khaliullin, G., Okamoto, S., Reehuis, M., Ivanov, A., He, H., ...
Neutron scattering was used to determine the spin structure and the magnon spectrum of the Mott--Hubbard insulator YTiO$_3$. The magnetic structure is complex, comprising substantial G-type and...
Quantum Behavior of Orbitals in Ferromagnetic Titanates: Novel Orderings and Excitations (2002)
We investigate the collective behavior of orbital angular momentum in the spin ferromagnetic state of a Mott insulator with t(2g) orbital degeneracy. The frustrated nature of the interactions leads...
Magnetic Order and Dynamics in an Orbitally Degenerate Ferromagnetic Insulator (2002)
Ulrich, C., Khaliullin, G., Okamoto, S., Reehuis, M., Ivanov, A., He, H., ...
Neutron scattering was used to determine the spin structure and the magnon spectrum of the Mott-Hubbard insulator YTiO3. The magnetic structure is complex, comprising substantial G-type and A-type...
Magnon softening and damping in the ferromagnetic manganites due to orbital correlations (2001)
Krivenko, S., Yaresko, A., Khaliullin, G., Fehske, H.
We present a theory for spin excitations in ferromagnetic metallic manganites and demonstrate that orbital fluctuations have strong effects on the magnon dynamics in the case these compounds are...
Horsch, P., Khaliullin, G., Oudovenko, V.
The density fluctuation spectrum $N({\bf k},\omega)$ is calculated for the t-J model in the low-doping regime using a slave-fermion method for the constrained fermions. The obtained results for...
Order from disorder: Quantum spin gap in magnon spectra of LaTiO_3 (2001)
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...
Density response of cuprates and renormalization of breathing phonons (2001)
We analyse the dynamical density fluctuation spectra for cuprates starting from the $t-J$ model in a slave-boson 1/N representation. The results obtained are consistent with diagonalization studies...
Spin Order due to Orbital Fluctuations: Cubic Vanadates (2001)
Khaliullin, G., Horsch, P., Oles, A. M.
We investigate the highly frustrated spin and orbital superexchange interactions in cubic vanadates. The fluctuations of $t_{2g}$ orbitals trigger a {\it novel mechanism of ferromagnetic...
Orbital liquid in three dimensional Mott insulator: $LaTiO_3$ (2000)
We present a theory of spin and orbital states in Mott insulator $LaTiO_3$. The spin-orbital superexchange interaction between $d^1(t_{2g})$ ions in cubic crystal suffers from a pathological...
Theory of anomalous magnon softening in ferromagnetic manganites (1999)
In metallic manganites with low Curie temperatures, a peculiar softening of the magnon spectrum close to the magnetic zone boundary has experimentally been observed. Here we present a theory of the...
Orbital polarons in the metal-insulator transition of manganites (1999)
The metal-insulator transition in manganites is strongly influenced by the concentration of holes present in the system. Based upon an orbitally degenerate Mott-Hubbard model we analyze two possible...
Orbital Polarons in the Metal-Insulator Transition of Manganites (1999)
The metal-insulator transition in manganites is strongly influenced by the concentration of holes present in the system. Based upon an orbitally degenerate Mott-Hubbard model we analyze two possible...
Orbital order out of spin disorder: How to measure the orbital gap (1999)
The interplay between spin and orbital degrees of freedom in the Mott-Hubbard insulator is studied by considering an orbitally degenerate superexchange model. We argue that orbital order and the...
Impurity-induced spin polarization and NMR line broadening in underdoped cuprates (1999)
Kilian, R., Krivenko, S., Khaliullin, G., Fulde, P.
We present a theory of magnetic (S=1) Ni and nonmagnetic Zn impurities in underdoped cuprates. Both types of impurities are shown to induce S=1/2 moments on Cu sites in the proximity of the impurity,...
Orbital Dynamics: The Origin of Anomalous Magnon Softening in Ferromagnetic Manganites (1999)
We study the renormalization of magnons by charge and coupled orbital-lattice fluctuations in colossal magnetoresistance compounds. The model considered is an orbitally degenerate double-exchange...
Local spin polarization in underdoped cuprates with impurities (1998)
Khaliullin, G., Kilian, R., Krivenko, S., Fulde, P.
We present a theory of magnetic (Ni) and nonmagnetic (Zn) impurities substituted into planar Cu sites in the normal state of underdoped cuprates exhibiting a spin gap. Both types of impurities induce...
Orbital dynamics: The origin of the anomalous optical spectra in ferromagnetic manganites (1998)
We discuss the role of orbital degeneracy in the transport properties of perovskite manganites, focusing in particular on the optical conductivity in the metallic ferromagnetic phase at low...
Spin and orbital excitation spectrum in the Kugel-Khomskii model (1997)
We discuss spin and orbital ordering in the twofold orbital degenerate superexchange model in three dimensions relevant to perovskite transition metal oxides. We focus on the particular point on the...
Impurity-induced moments in underdoped cuprates (1997)
Khaliullin, G., Kilian, R., Krivenko, S., Fulde, P.
We examine the effect of a nonmagnetic impurity in a two-dimensional spin liquid in the spin-gap phase, employing a drone-fermion representation of spin-1/2 operators. The properties of the local...
Theory of the density fluctuation spectrum of strongly correlated electrons (1996)
The density response function $N(q,\omega)$ of the two-dimensional $t-J$ model is studied starting from a mixed gauge formulation of the slave boson approach. Our results for $N(q, \omega)$ are in...