Unique insights into an exotic matter state

December 18, 2018

The properties of the matter, which surrounds us in our everyday life, are typically the result of complex interactions between electrons. These electrically-charged particles are one of the fundamental building blocks of nature. By now, they are well researched, and theoretical physics has determined the electronic structure of the majority of matter. However, how matter behaves under extreme conditions is still largely unexplained. These can be found in places where very high pressure and high temperatures prevail, such as in the interior of stars and planets. Here, matter exists in an exotic state on the border between solid, liquid and gas. A research group at Kiel University and the Helmholtz-Zentrum Dresden-Rossendorf has now developed a new method to accurately describe the dynamic properties of this so-called "warm dense matter" for the first time. They have published their specially-developed computer simulations in the current issue of the renowned scientific journal Physical Review Letters.

Today, warm dense matter can also be produced experimentally in large research institutions, for example using the high-intensity lasers or free-electron lasers at the European XFEL in Hamburg and Schleswig-Holstein. Powerful lasers are used to compress and heat the matter enormously. It can then be examined using another laser. A measurement of the so-called X-ray Thomson scattering - in other words, how the laser beam is scattered by free electrons - makes it possible to determine many properties of warm dense matter, such as its electrical conductivity, or its absorption of radiation.

However, this requires a comprehensive theoretical understanding of warm dense matter, and in particular of the so-called dynamic structure factor of the compressed hot electrons. To date, science has not been able to describe this reliably and accurately. The interaction of the various factors which play a role here is just too complex, at temperatures of up to ten million degrees Celsius, and a density which usually only occurs in solids. In addition to the intense heat, this also includes the so-called Coulomb interaction, occurring when two negatively-charged electrons repel each other, as well as numerous quantum mechanical effects.

The research team under the direction of Michael Bonitz, professor of theoretical physics at the CAU, has now achieved a breakthrough: using complex simulations performed on supercomputers, they have developed a computational method, with which they could precisely describe the dynamic structure factor of electrons in warm dense matter for the first time. To achieve this, they further extended their own quantum Monte Carlo simulations, developed in recent years.

"Our new data provides unique insights," explained Bonitz. "Remarkably, it has already been shown that the exact description of the repulsion between negative charges results in a significantly-modified Thomson scattering signal, in particular to a drastically changed plasmon dispersion, compared with previous theories." These predictions will now be checked experimentally. The results thus obtained are of extraordinary importance for the interpretation of state-of-the-art experiments with warm dense matter, such as those which will begin shortly at the European XFEL. For example, they can be used to determine key properties, such as the temperature of the electrons, or the velocity of propagation of waves which arise if the matter is bombarded with lasers.
-end-


Kiel University

Related Electrons Articles from Brightsurf:

One-way street for electrons
An international team of physicists, led by researchers of the Universities of Oldenburg and Bremen, Germany, has recorded an ultrafast film of the directed energy transport between neighbouring molecules in a nanomaterial.

Mystery solved: a 'New Kind of Electrons'
Why do certain materials emit electrons with a very specific energy?

Sticky electrons: When repulsion turns into attraction
Scientists in Vienna explain what happens at a strange 'border line' in materials science: Under certain conditions, materials change from well-known behaviour to different, partly unexplained phenomena.

Self-imaging of a molecule by its own electrons
Researchers at the Max Born Institute (MBI) have shown that high-resolution movies of molecular dynamics can be recorded using electrons ejected from the molecule by an intense laser field.

Electrons in the fast lane
Microscopic structures could further improve perovskite solar cells

Laser takes pictures of electrons in crystals
Microscopes of visible light allow to see tiny objects as living cells and their interior.

Plasma electrons can be used to produce metallic films
Computers, mobile phones and all other electronic devices contain thousands of transistors, linked together by thin films of metal.

Flatter graphene, faster electrons
Scientists from the Swiss Nanoscience Institute and the Department of Physics at the University of Basel developed a technique to flatten corrugations in graphene layers.

Researchers develop one-way street for electrons
The work has shown that these electron ratchets create geometric diodes that operate at room temperature and may unlock unprecedented abilities in the illusive terahertz regime.

Photons and electrons one on one
The dynamics of electrons changes ever so slightly on each interaction with a photon.

Read More: Electrons News and Electrons Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.