Electronic Correlations in Solids

May 14, 2007

The word “correlation” means “mutual dependence” or “interrelation” and the term “electronic correlation” summarises all effects arising from the mutual repulsion of negatively charged electrons. More precisely, it refers to how this repulsion influences the spatial and dynamical motion of the electrons. The concept can be likened to the behaviour of people in a crowded market place: people and electrons have to avoid each other so as not to bump into one other, something that greatly influences their motion.

At the EPL symposium, “Physics In Our Times” held on May, 9 at the Fondation Del Duca de l’Institut de France, Paris Dieter Vollhardt, professor of theoretical condensed matter physics at the University of Augsburg in Germany explained his team’s new theoretical method, dynamical mean-field theory, which can describe the whole range of materials from weakly interacting and strongly localised models within one framework.

Electronic correlations in solids may lead to spectacular effects, such as metal-to-insulator transitions, high-temperature superconductivity, and colossal magneto-resistance. These are not only interesting for fundamental research but also for technological applications in areas such as sensors, magnetic storage, switches and cables.

For technology to progress we need theoretical techniques that can help us understand and predict the behaviour of new materials. There are many examples of materials that show great promise for technological applications but which cannot be described by conventional theories.

For example, high-temperature superconducting materials and some high-density magnetic storage materials are still not well understood. This is because such theories either treat each electron in a material as weakly interacting with other electrons, or assume that electron-electron repulsion dominates, causing the electrons to be strongly localised to individual atoms.

Together with colleagues Antoine Georges, Walter Metzner and Gabriel Kotliar, one of Prof. Vollhardt’s most recent successes has been to develop and apply a new theoretical method called dynamical mean-field theory. In combination with other techniques, this theory can, in principle, describe the whole range of materials from weakly interacting and strongly localised models within one framework. One of the steps in the theory imagines the material in a higher dimension space and then approximates an infinite number of dimensions.

Although this assumption sounds radical, it significantly simplifies the equations and leads to accurate predictions. Indeed, this theory - for which the physicists jointly received the Europhysics Prize in 2006 - has already been successfully applied to many correlated electron materials, in particular to transition metals and their oxides.

Prof. Vollhardt believes that future directions of research in his field will include such diverse topics as investigating electronic correlations in inhomogeneous materials and interfaces, complex ordering phenomena on frustrated structures, non-equilibrium physics and correlation effects in biological systems.

Source: Institute of Physics

Explore further: Meet the high-performance single-molecule diode

Related Stories

Meet the high-performance single-molecule diode

July 29, 2015

A team of researchers from Berkeley Lab and Columbia University has passed a major milestone in molecular electronics with the creation of the world's highest-performance single-molecule diode. Working at Berkeley Lab's Molecular ...

Short wavelength plasmons observed in nanotubes

July 28, 2015

The term "plasmons" might sound like something from the soon-to-be-released new Star Wars movie, but the effects of plasmons have been known about for centuries. Plasmons are collective oscillations of conduction electrons ...

Wafer-thin material heralds future of wearable technology

July 27, 2015

UOW's Institute for Superconducting and Electronic Materials (ISEM) has successfully pioneered a way to construct a flexible, foldable and lightweight energy storage device that provides the building blocks for next-generation ...

Quantum networks: Back and forth are not equal distances

July 27, 2015

Quantum technology based on light (photons) has great potential for radically new information technology based on photonic circuits. Up to now, the photons in quantum photonic circuits have behaved in the same way whether ...

Recommended for you

New device converts DC electric field to terahertz radiation

August 4, 2015

Terahertz radiation, the no-man's land of the electromagnetic spectrum, has long stymied researchers. Optical technologies can finagle light in the shorter-wavelength visible and infrared range, while electromagnetic techniques ...

The resplendent inflexibility of the rainbow

August 4, 2015

Children often ask simple questions that make you wonder if you really understand your subject. An young acquaintance of mine named Collin wondered why the colors of the rainbow were always in the same order—red, orange, ...

For faster battery charging, try a quantum battery?

August 3, 2015

(Phys.org)—Physicists have shown that a quantum battery—basically, a quantum system such as a qubit that stores energy in its quantum states—can theoretically be charged at a faster rate than conventional batteries. ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.