Vollhardt's group

	An Introduction
	Jerusalem Lectures
	Varenna Lectures

Publications

Bachelor Theses

Diploma Theses

PhD Theses

Habilitation Theses

Lectures and Seminars

Talks

Elektronische Korrelationen und Magnetismus: Eine Einführung

What do we mean when we speak of "electronic correlations" and "magnetism"? In the above article (only available in German) these terms are explained on a simple level. Furthermore the importance of theoretical models for the investigation of basic questions in physics is discussed.

Areas of Research

Realistic modelling of strongly correlated electronic systems

We develop and apply the novel computational scheme LDA+DMFT to investigate electronically correlated materials from first principles. LDA+DMFT is based on a combination of conventional methods for computing electronic band structures, e.g., the local density approximation (LDA), with the dynamical mean-field theory (DMFT) for correlated electron systems. The LDA+DMFT approach is employed in particular to calculate photoemission and absorption spectra of transition metal oxides in close collaboration with experimental groups.

Metal-insulator transitions in electronic systems

Phase transitions between metallic, non-metallic, magnetically ordered and non-ordered states in correlated and/or disordered electronic systems are investigated within dynamical mean-field theory (DMFT) plus finite temperature quantum Monte-Carlo techniques (QMC), as well as by the numerical renormalization group and other techniques. Thereby the influence of disorder, frustration and doping on the transitions is studied.

Microscopic theory of magnetism

We investigate the microscopic conditions for the stability of long-range ordered magnetic states in strongly correlated insulators and metals. A broad range of theoretical tools (rigorous methods, perturbation theory at weak and strong coupling, low and high dimensions, variational procedures, quantum Monte-Carlo calculations, numerical renormalization group, etc.) is employed for this purpose.

Correlated electrons in nonequilibrium

The real-time dynamics of correlated electrons are studied using dynamical mean-field-theory for nonequilibrium. This approach can be used in particular to describe pump-probe experiments, in which the sample is excited by a first laser pulse and analyzed with a second laser pulse after a controlled time delay.

Correlated bosonic systems

The properties of correlated lattice bosons are investigated by means of the newly developed bosonic dynamical mean-field theory (B-DMFT). In this approach the dynamic coupling between normal and condensed bosons is explicitly included.

Development of new theoretical methods

We develop analytical and numerical approaches for the non-perturbative investigation of electronic correlation phenomena in quantum mechanical lattice models.

Introductory literature

Elektronische Korrelationen und Magnetismus: Eine Einführung (in German) (pdf)

Strongly Correlated Materials: Insights from Dynamical Mean-Field Theory, G. Kotliar and D. Vollhardt, Physics Today (March 2004)

Elektronische Korrelationen im Festkörper (in German), Physik Journal (August/September 2010) (pdf)

Lecture Notes:

Investigations of correlated electron systems using the limit of high dimensions

Strong-coupling approaches to correlated fermions

Theoretical Physics III