Exciton doublet in the Mott-Hubbard LiCuVO$_4$ insulator identified by spectral ellipsometry (2009)
Matiks, Y., Horsch, P., Kremer, R. K., Keimer, B., Boris, A. V.
Spectroscopic ellipsometry was used to study the dielectric function of LiCuVO$_{4}$, a compound comprised of chains of edge-sharing CuO$_4$ plaquettes, in the spectral range (0.75 - 6.5) eV at...
Thermally activated Peierls dimerization in ferromagnetic spin chains (2008)
Sirker, J., Herzog, A., Oles, A. M., Horsch, P.
We demonstrate that a Peierls dimerization can occur in ferromagnetic spin chains activated by thermal fluctuations. The dimer order parameter and entanglement measures are studied as functions of...
Absence of Hole Confinement in Transition Metal Oxides with Orbital Degeneracy (2008)
Daghofer, M., Wohlfeld, K., Oles, A. M., Arrigoni, E., Horsch, P.
We investigate the spectral properties of a hole moving in a two-dimensional Hubbard model for strongly correlated t_2g electrons. Although superexchange interactions are Ising-like, a...
Magnetism of one-dimensional Wigner lattices and its impact on charge order (2007)
Daghofer, M., Noack, R. M., Horsch, P.
The magnetic phase diagram of the quarter-filled generalized Wigner lattice with nearest- and next-nearest-neighbor hopping t_1 and t_2 is explored. We find a region at negative t_2 with fully...
Fractional charges and spin-charge separation in one-dimensional Wigner lattices (2006)
We study density response N(k,omega) and one-particle spectra A(k,omega) for a Wigner lattice model at quarter filling using exact diagonalization. We investigate these observables for models with...
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...
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...
Self-localization of composite spin-lattice polarons (2006)
Prelovsek, P., Zeyher, R., Horsch, P.
Self-localization of holes in the Holstein t-J model is studied in the adiabatic limit using exact diagonalization and the retraceable path approximation. It is shown that the critical...
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...
Wigner crystallization in Na(3)Cu(2)O(4) and Na(8)Cu(5)O(10) chain compounds (2005)
Horsch, P., Sofin, M., Mayr, M., Jansen, M.
We report the synthesis of novel edge-sharing chain systems Na(3)Cu(2)O(4) and Na(8)Cu(5)O(10), which form insulating states with commensurate charge order. We identify these systems as...
Helicoidal magnetic order in the spin-chain compound NaCu2O2 (2005)
Capogna, L., Mayr, M., Horsch, P., Raichle, M., Kremer, R. K., Sofin, M., ...
Helicoidal magnetic order in a clean copper oxide spin chain compound (2004)
Capogna, L., Mayr, M., Horsch, P., Raichle, M., Kremer, R. K., Sofin, M., ...
We report susceptibility, specific heat, and neutron diffraction measurements on NaCu$_2$O$_2$, a spin-1/2 chain compound isostructural to LiCu$_2$O$_2$, which has been extensively investigated....
Planar Cu and O hole densities in high-Tc cuprates determined with NMR (2004)
Haase, J., Sushkov, O. P., Horsch, P., Williams, G. V. M.
The electric hyperfine interaction observable in atomic spectroscopy for O and Cu ions in various configurations is used to analyze the quadrupole splitting of O and Cu nuclear magnetic resonance...
Manganites at quarter filling: Role of Jahn-Teller interactions (2004)
Bała, J., Horsch, P., Mack, F.
We have analyzed different correlation functions in a realistic spin-orbital model for half-doped manganites. Using a finite-temperature diagonalization technique the CE phase was found in the...
CE correlations in a spin-orbital model for half-doped manganites (2004)
Using a finite-temperature diagonalization technique for a root8 x root8 site cluster, the charge-exchange phase was found to be stabilized together with charge order by the cooperative Jahn-Teller...
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...
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...
Planar Cu and O hole densities in high-Tc cuprates determined with NMR (2003)
Haase, J., Sushkov, O. P., Horsch, P., Williams, G. V. M.
The electric hyperfine interaction observable in atomic spectroscopy for O and Cu ions in various configurations is used to analyze the quadrupole splitting of O and Cu nuclear magnetic resonance...
Temperature dependence of optical spectral weights in quarter-filled ladder systems (2002)
Aichhorn, M., Horsch, P., Cuoco, M.
The temperature dependence of the integrated optical conductivity I(T) reflects the changes of the kinetic energy as spin and charge correlations develop. We calculated I(T) in the frame of a t-J-V...
Orbital polarons in LaMnO3 (2002)
Bała, J., Oleś, A. M., Horsch, P.
We investigate the spectral functions and orbital correlation functions relative to the position of an e,. hole moving in the ferromagnetic plane of orbitally ordered LaMnO3. Polarization of orbitals...
Quasiparticles and the structure of orbital polarons in ferromagnetic LaMnO3 (2002)
Bała, J., Oleś, A. M., Horsch, P.
We investigate the spectral functions and orbital-correlation functions relative to the position of an e(g) hole moving in the ferromagnetic plane of orbitally ordered LaMnO3. Solving this problem in...
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...
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...
On the electron-energy loss spectra and plasmon resonance in cuprates (1999)
The consequences of the non-Drude charge response in the normal state of cuprates and the effect of the layered structure on electron-energy loss spectra are investigated, both for experiments in the...
A new view of the electronic structure of the spin-Peierls compound alpha'-NaV2O5 (1998)
The present understanding of the electronic and magnetic properties of $\alpha'$-NaV$_2$O$_5$ is based on the hypothesis of strong charge disproportionation into V$^{4+}$ and V$^{5+}$, which is...
Carmelo, J. M. P., Horsch, P., Ovchinnikov, A. A., Campbell, D. K., Castro Neto, A. H., Peres, N. M. R.
Spatial Structure of Spin Polarons in the t-J Model (1997)
The deformation of the quantum Neel state induced by a spin polaron is analyzed in a slave fermion approach. Our method is based on the selfconsistent Born approximation for Green's and the wave...
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...
Critical behavior of the S=3/2 antiferromagnetic Heisenberg chain (1996)
Hallberg, K., Wang, X. Q. G., Horsch, P., Moreo, A.
Using the density-matrix renormalization-group technique we study the long-wavelength properties of the spin S=3/2 nearest-neighbor Heisenberg chain. We obtain an accurate value for the spin velocity...
Superconducting pairing of spin polarons in the t-J model (1995)
Plakida, N M, Oudovenko, V S, Horsch, P, Liechtenstein, A I
The pairing of quasiparticles in a CuO_2 plane is studied within a spin polaron formulation of the t-t^{'}-J model. Our numerical solution of the Eliashberg equations unambiguously shows d-wave...
Superconducting pairing of spin polarons in the t-J model (1995)
Plakida, N. M., Oudovenko, V. S., Horsch, P., Liechtenstein, A. I.
The pairing of quasiparticles in a CuO$_2$ plane is studied within a spin polaron formulation of the $t$-$t^{'}$-$J$ model. Our numerical solution of the Eliashberg equations unambiguously shows...
Hallberg, K. A., Horsch, P., Martinez, G.
We use the density-matrix renormalization group technique developed by White \cite{white} to calculate the spin correlation functions $=(-1)^l \omega(l,N)$ for isotropic Heisenberg rings up to $N=70$...
Elektronische Zustandsdichte und Supraleitung in A15-Verbindungen. (1977)
Fruehjahrstagung DPG, Festkoerperphysik, Muenster, 7.-12.Maerz 1977. Verhandlungen der Deutschen Physikalischen Gesellschaft, R.6, Bd 12(1977) S.434
A new aspect of superconductivity in A-15 compounds. (1977)
Zeitschrift fuer Physik B, 27(1977) S.153-60
Fruehjahrstagung DPG, Festkoerperphysik, Muenster, 7.-12.Maerz 1977. Verhandlungen der Deutschen Physikalischen Gesellschaft, R.6, Bd 12(1977) S.434