Professor Keun Su Kim(Department of Physics), Yonsei University, and his team experimentally found the ‘electronic structure of liquid metals’predicted by Nobel Prize winners Philip Anderson and Neville Mott in the 1960s. The results of this research were published on August 5(Korean Time)in the prominent International journal Nature.

Electronic structure is a correlation between the energy and momentum(wave number)of electronic waves in a material, solid physicists describe the electrical and optical properties of the material based on the electronic structure. In the case of crystalline solids in which the atoms constituting the material are regularly arranged, the electronic structure can be easily described, but in materials such as liquids or amorphous solids(glass)where the form can be freely changed and the atomic arrangement is irregular, it is very difficult to explain the electronic structure theoretically.

Nobel Prize winners Philip Anderson and Neville Mott presented a theoretical model explaining the ‘electronic structure of liquid metals’after their respective efforts in the 1960s, but it has never been experimentally discovered in the last half century.

In order to observe this experimentally, Professor Keun Su Kim's team approached the method of measuring the interfacial electronic structure of liquid metals and crystal solids, unlike the classical method of measuring liquid metals directly. The researchers sprayed liquid alkali metals(sodium, potassium, rubidium, cesium) on the surface of a crystalline solid called’black phosphorus(black phosphorus)'. Electrons added to the black phosphorus crystal solid collide with irregularly distributed alkali metal atoms and have features such as ‘electronic structure of liquid metal’.

As a result of this precise measurement, the research team found a unique electronic structure and ‘pseudogap’in the form of a backward bend that Anderson and Mott had predicted in the interfacial electronic structure. Analog gap is a term named by Neville Mott in 1968 that refers to an incomplete energy gap that appears in electronic structures when atoms are irregularly arranged.

The results of this experiment are significant because the high-temperature superconducting phenomenon that is the basis of power transport without energy loss is also shown when heterogeneous atoms are added to crystalline solids. Because the phenomenon of high temperature superconductivity, which is an unsolved difficulty in aggregated material physics, has appeared a ‘pseudogap’that is unknown to the electronic structure, it was hoped that understanding this will solve the secret of high temperature superconductivity.

Professor Keun Su Kim of Yonsei said that “the impact of collisions with irregularly arranged heterogeneous atoms can explain the similarity gap”and “will provide important clues to understanding high-temperature superconducting phenomena.”

This research was conducted with the support of Yonsei University's Yonsei Signature Research Cluster project and the Basic research project(mid-level research, leading research, etc.) of the Ministry of Science and Technology Information and Communication. YONSEI Signature Research Cluster project is a research support project introduced by Yonsei University this year to foster representative research fields, and by focusing on the fields that can produce world-class research results, Yonsei University has produced prominent achievements.