Universal behaviour detected in Mott metal-insulator transition

December 16, 2016, Goethe University Frankfurt am Main
Electrons embedded in the atomic lattice – the components of a solid. The mutual repulsion of the electrons prevents them from coming into close contact. This impedes the electron flow and the system can become an insulator. Credit: Dr. Ulrich Tutsch

Whether water freezes to ice, iron is demagnetized or a material becomes superconducting – for physicists there is always a phase transition behind it. They endeavour to understand these different phenomena by searching for universal properties. Researchers at Goethe University Frankfurt and Technische Universität Dresden have now made a pioneering discovery during their study of a phase transition from an electrical conductor to an insulator (Mott metal-insulator transition).

According to Sir Nevill Francis Mott's prediction in 1937, the mutual repulsion of charged electrons, which are responsible for carrying electrical current, can cause a metal-insulator transition. Yet, contrary to common textbook opinion, according to which the phase transition is determined solely by the electrons, it is the interaction of the electrons with the atomic lattice of the solid which is the determinant factor. The researchers have reported this in the latest issue of the Science Advances journal.

The research group, led by Professor Michael Lang of the Physics Institute at Goethe University Frankfurt, succeeded in making the discovery with the help of a homemade apparatus which is unique worldwide. It allows the measurement of length changes at low temperatures under variable external pressure with extremely high resolution. In this way, it was possible to prove experimentally for the first time that it is not just the electrons which play a significant role in the phase transition but also the atomic lattice—the solid's scaffold.

"These experimental results will herald in a paradigm shift in our understanding of one of the key phenomena of current condensed matter research," says Professor Lang. The Mott metal-insulator transition is namely linked to unusual phenomena, such as high-temperature superconductivity in copper oxide-based materials. These offer tremendous potential for future technical applications.

The theoretical analysis of the experimental findings is based on the fundamental notion that the many particles in a system close to a phase transition not only interact with their immediate neighbours but also "communicate" over long distances with all other particles. As a consequence, only overarching aspects are important, such as the system's symmetry. The identification of such universal properties is thus the key to understanding .

"These new insights open up a whole new perspective on the Mott metal-insulator transition and permit more sophisticated theoretical modelling of the phase transition," explains Dr. Markus Garst, Senior Lecturer at the Institute of Theoretical Physics of Technische Universität Dresden.

Explore further: The metal-insulator transition depends on the mass of the Dirac electrons

More information: E. Gati et al. Breakdown of Hookes law of elasticity at the Mott critical endpoint in an organic conductor, Science Advances (2016). DOI: 10.1126/sciadv.1601646

Related Stories

Recommended for you

How a particle may stand still in rotating spacetime

May 25, 2018

When a massive astrophysical object, such as a boson star or black hole, rotates, it can cause the surrounding spacetime to rotate along with it due to the effect of frame dragging. In a new paper, physicists have shown that ...

Long live the doubly charmed particle

May 25, 2018

Finding a new particle is always a nice surprise, but measuring its characteristics is another story and just as important. Less than a year after announcing the discovery of the particle going by the snappy name of Ξcc++ (Xicc++), ...

How can you tell if a quantum memory is really quantum?

May 23, 2018

Quantum memories are devices that can store quantum information for a later time, which are usually implemented by storing and re-emitting photons with certain quantum states. But often it's difficult to tell whether a memory ...

0 comments

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.