17 Result(s)

Chapter

Quantum Percolation in Disordered Structures

Many solids, such as alloys or doped semiconductors, form crystals consisting of two or more chemical species. In contrast to amorphous systems, they show a regular, periodic arrangement of sites but the diffe...

G. Schubert, H. Fehske in Quantum and Semi-classical Percolation and… (2009)

Chapter

Numerical Solution of the Holstein Polaron Problem

Noninteracting itinerant electrons in a solid occupy Bloch one-electron states. Phonons are collective vibrational excitations of the crystal lattice. The basic electron-phonon (EP) interaction process is the ...

H. Fehske, S. A. Trugman in Polarons in Advanced Materials (2007)

Article

Local distribution approach to disordered binary alloys

We study the electronic structure of the binary alloy and (quantum) percolation model. Our study is based on a self-consistent scheme for the distribution of local Green functions. We obtain detailed results ...

A. Alvermann, H. Fehske in The European Physical Journal B - Condense… (2005)

Article

Nature of the Peierls- to Mott-insulator transition in 1D

In order to clarify the physics of the crossover from a Peierls band insulator to a correlated Mott-Hubbard insulator, we analyze ground-state and spectral properties of the one-dimensional half-filled Holstei...

H. Fehske, A.P. Kampf, M. Sekania… in The European Physical Journal B - Condense… (2003)

Article

Interplay of charge, spin, orbital and lattice correlations in colossal magnetoresistance manganites

We derive a realistic microscopic model for doped colossal magnetoresistance manganites, which includes the dynamics of charge, spin, orbital and lattice degrees of freedom on a quantum mechanical level. The m...

A. Weiße, H. Fehske in The European Physical Journal B - Condense… (2002)

Article

Pairing Susceptibility of Strongly Correlated Electrons Weakly Coupled to the Lattice

We analyze numerical exact results for the d-wave pairingcorrelations in the two-dimensional Holstein tJ model in terms of aneffective independent boson approach.

H. Fehske, G. Wellein, H. B¨ttner in Journal of Superconductivity (1999)

Article

A new model to describe the physics of

In the past different models for the magnetic salt vanadyl pyrophosphate (VO)₂P₂O₇ were discussed. Neither a spin ladder nor an alternating chain are capable to describe recently measured magnetic excitations. In...

A. Weiße, G. Bouzerar, H. Fehske in The European Physical Journal B - Condense… (1999)

Article

Spectral properties of the 2D Holstein polaron

The two-dimensional Holstein model is studied by means of direct Lanczos diagonalization preserving the full dynamics and quantum nature of phonons. We present numerical exact results for the single-particle s...

H. Fehske, J. Loos, G. Wellein in Zeitschrift für Physik B Condensed Matter (1997)

Article

Electron correlations and quantum lattice vibrations in strongly coupled electron-phonon systems: A variational slave boson approach

We investigate the ground-state properties of the two-dimensional Hubbard model with an additional Holstein-type electron-phonon coupling on a square lattice. The effects of quantum lattice vibrations on the s...

U. Trapper, H. Fehske, M. Deeg, H. Büttner in Zeitschrift für Physik B Condensed Matter (1994)

Article

Dynamic spin and charge susceptibilities in thet−J model

Based on the spin-rotation-invariant formulation of the Kotliar Ruckenstein slave-boson representation, the paramagnetic spin and charge susceptibilities in thet-J model are calculated. Analyzing the static spin ...

M. Deeg, H. Fehske, S. Körner, S. Trimper… in Zeitschrift für Physik B Condensed Matter (1994)

Article

Polaron formation and hop** conductivity in the Holstein-Hubbard model

On the basis of the Holstein-Hubbard model the formation of polarons at finite densities is investigated by means of a variational approach appropriate for describing squeezing and correlation effects. An effe...

H. Fehske, D. Ihle, J. Loos, U. Trapper… in Zeitschrift für Physik B Condensed Matter (1994)

Chapter

The Phase Diagram of the 2D Holstein-t-J Model

The importance of both strong antiferromagnetic Coulomb correlations as well as strong electron-phonon (EP) interactions has become increasingly recognized as being essential in understanding the superconducti...

H. Fehske, H. Röder in Nonlinear Coherent Structures in Physics and Biology (1994)

Chapter

A Variational Slave Boson Approach to the Holstein-Hubbard Model

Research on the high-T _c cuprates has focused, once again, interest on strongly coupled electron-phonon (EP) systems. Although it is widely believed that most o...

H. Fehske, U. Trapper, M. Deeg, H. Büttner in Nonlinear Coherent Structures in Physics a… (1994)

Article

Slave-boson phase diagram of the two-dimensional extended Hubbard model: Influence of electron-phonon coupling

We present a detailed study of the extended Hubbard-Peierls model on a square lattice using the slave-boson method proposed by Kotliar and Ruckenstein. The emphasis is on the investigation of the ground state ...

M. Deeg, H. Fehske, H. Büttner in Zeitschrift für Physik B Condensed Matter (1993)

Article

Slave boson mean field theory for the 2-D Peierls-Hubbard system

Adapting the Kotliar-Ruckenstein slave boson approach to the Hubbard model with an additional local electronphonon interaction, we have studied the stability of the ground state against (π, π) and (π, 0) Peier...

M. Deeg, H. Fehske, H. Büttner in Zeitschrift für Physik B Condensed Matter (1992)

Chapter and Conference Paper

Some remarks on the spin fluctuation theories for itinerant electrons

B. Lorenz, H. Fehske in Static Critical Phenomena in Inhomogeneous Systems (1984)