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Discovery of an electronic glass state

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Posted June 27, 2013

Dr. Fumitaka Kagawa at the University of Tokyo’s Department of Applied Physics and his colleagues have discovered that a charge-cluster glass evolves in an organic conductor on cooling.

Freezing of charge fluctuations towards low temperatures. © Fumitaka Kagawa.

Freezing of charge fluctuations towards low temperatures. © Fumitaka Kagawa.

Many atoms and molecules in a liquid will form regular crystalline structures when frozen slowly, but there are many that will form a non-periodic glass state when cooled quickly. In strongly correlated electron systems, a group of substances in which electrons interact strongly, a phenomenon is often observed where itinerant electrons behaving like a liquid localize to form a crystalline structure at low temperatures.

Despite the apparent similarity between the crystallization of such strongly correlated electron systems and ordinary liquids, the vitrification of strongly correlated electron systems by preventing crystallization through rapid cooling had not been observed until now.

Through time-resolved transport measurements and X-ray diffraction, the researchers revealed that in the charge-liquid state two-dimensional charge clusters evolve and fluctuate extremely slowly (<10–100 Hz). On further cooling, the cluster dynamics freezes, and a charge-cluster glass is formed.

So far, glassy states are known to appear in supercooled viscous liquids and electron systems with randomly distributed dopants. The present organic conductor is nominally dopant-free and believed to be a clean system; therefore the electronic glassy state in the organic conductor is probably conceptually new. This discovery is expected to open a new avenue for understanding the mechanism of glass formation.

Dr Kagawa was working in collaboration with graduate student Takuro Sato, Dr. Kazuya Miyagawa and Prof. Kazushi Kanoda (the University of Tokyo), Prof. Yoshinori Tokura (the University of Tokyo and RIKEN Group director), and Dr. Kensuke Kobayashi, Prof. Reiji Kumai, and Prof. Youichi Murakami (the Institute of Materials Structure Science at KEK).

This research was published online in Nature Physics on 10 June 2013.

Source: University of Tokyo

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