New light on solid state: How fast flashes of light might change the properties of solid matter?

In the laboratories for the physics of complex systems and physics of condensed matter at the Weizmann Institute, an unusual phenomenon was discovered which, according to the researchers, may in the future lead to the development of electronic systems that are much faster than the existing ones

Speed ​​is the name of the game in the research group of Prof. Nirit Dudovitz from the Department of Physics of Complex Systems at the Weizmann Institute of Science. The members of the group examine ultra-short phenomena in nature, using flashes of light whose speed is measured in attoseconds (an attosecond is one billionth of a billionth of a second). These short flashes of light allow scientists to observe various quantum processes, from quantum tunneling to the disintegration or combination of molecules in certain chemical reactions. Until recently, these advanced studies and experiments were performed on matter in a gaseous state of aggregation. Then the research students Ayelet Ozan and Gal Orenstein entered Prof. Dudovitz's laboratory. They suggested trying to create the rapid flashes of light in solid matter. A substance in a gaseous state consists of separated atoms, where each atom has a small number of electrons, concentrated around the nucleus. In contrast, a crystal of a solid substance consists of many atoms arranged together and a huge amount of electrons scattered throughout the crystal.

Such experiments, in solid material, have already been carried out in several laboratories in the world. Since this is an experimental and theoretical challenge, which requires a significant change in the direction of her research, Prof. Dudovitz was debating whether to choose to move forward in this direction. Still, the enthusiasm of the research students swept her away, and they began to plan and build the experiment, in collaboration with Prof. Binghai Yan and his group members from the Department of Condensed Matter Physics at the institute.

The first experiments led to results that the scientists called "strange". And here it might be worth remembering that the scientist and science fiction writer, Isaac Asimov, said that "the most important phrase in science is 'it's strange...'". The resulting strange phenomenon showed that the spectrum of the rapid flashes consists of a kind of rainbow of "hills and valleys". For many months the scientists tried to understand the origin of this special spectral shape and what information can be obtained from it.

The electron, which is a quantum particle, can exist in a superposition of quantum states. For example, being at the same time in several different states characterized by different energy. The scientists tried to understand the relationship between these energy levels (the quantum state of the electron) and the spectrum of the rapid flashes.

The insight, as often happens, appeared suddenly, when the scientists noticed that certain superpositions of the electron create a kind of "lens", which concentrates the emission of the short flashes into "hills" that appear in the measured spectrum.

"The structure of energy levels in a material determines its basic properties," says Prof. Dudovitz. "In the future, we hope to measure the ability of laser light at high intensities to 'momentarily' change the structure of the levels - and thus also the properties of the material. For example, we may measure a very rapid change in the properties of the material, which turns from an insulator to a conductor and back again. The new understanding we achieved may lead, in the future, to the creation of a new type of electronics, in which various processes take place at much greater speeds than anything we know today."

The new results and insights, in their way, already set new ambitions. In Prof. Dudovitz's laboratory, they are already thinking about the ways in which it will be possible to produce a dynamic measurement, similar to a video film, which will show, in "slow motion", exactly how the energy levels of the measured electron change, while carrying out processes whose natural duration is measured in attoseconds.

More of the topic in Hayadan:

• Progress towards a quantum state of aggregation: a supersolid
• A photon and an electron meet inside a photonic crystal
• at lightning speed