Discovery that Thin Hydrogen Films are in a State on the Verge of Superfluidity
December 27, 2019 Keio University
A research group including Takahiko Makiuchi, a doctoral student at the Keio University Graduate School of Science and Technology (at the time of research; currently a postgraduate researcher at the University of Tokyo Graduate School of Engineering, Saitoh Spin Quantum Rectification ERATO program) and Professor Keiya Shirahama and Yusuke Nago, a research associate, of the Faculty of Science and Technology discovered that thin films of hydrogen molecules remain in a liquid state at extremely low temperatures and exist on the verge of superfluidity.
Similar to the superconductivity of metals, superfluidity is a dramatic quantum phenomenon that occurs at low temperatures, but it is only observed in very limited substances such as liquid helium. Molecular hydrogen (H2) has been attracting attention as one of the few candidate substances that can exhibit superfluidity. From elastic measurements of thin hydrogen films, in this study, it was discovered that the surface of the thin films behaves like a liquid down to an extremely low temperature of minus 272 degrees Celsius (absolute temperature of 1 kelvin) and are in a state on the verge of superfluidity. This finding is groundbreaking as it quantitively showed for the first time how close hydrogen is to being a superfluid, as well as opening up the possibility of making superfluid hydrogen a reality through new methods such as the application of high-frequency sound waves. Hydrogen is not only important for the formation of the universe and life, but there are also expectations that it will develop superconductivity under extremely high pressure. The realization of a superfluid hydrogen will not only demonstrate an aspect of hydrogen's diversity but is also expected to contribute greatly to the development of science.
The outcomes of this research were published in the American scientific journal "Physical Review Letters" on December 13, 2019 (local time).
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