Superconducting Niobium Calorimeter for Studies of Adsorbed Helium Monolayers
| Autor: | Hiroshi Fukuyama, Koki Tokeshi, Jun Usami, Tomohiro Matsui |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Superconductivity
Materials science Hydrogen Condensed Matter - Superconductivity Analytical chemistry Niobium chemistry.chemical_element FOS: Physical sciences Atmospheric temperature range Condensed Matter Physics 01 natural sciences Heat capacity Atomic and Molecular Physics and Optics 010305 fluids & plasmas Calorimeter Superconductivity (cond-mat.supr-con) Condensed Matter - Other Condensed Matter Deuterium chemistry Condensed Matter::Superconductivity 0103 physical sciences General Materials Science 010306 general physics Helium Other Condensed Matter (cond-mat.other) |
| Popis: | We developed a calorimeter with a vacuum container made of superconducting niobium (Nb) to study monolayers of helium adsorbed on graphite which are prototypical two-dimensional quantum matters below 1 K. Nb was chosen because of its small specific heat in the superconducting state. It is crucially important to reduce the addendum heat capacity ( $$C_\mathrm{{ad}}$$ ) when the specific surface area of substrate is small. Here we show details of design, construction and results of $$C_\mathrm{{ad}}$$ measurements of the Nb calorimeter down to 40 mK. The measured $$C_\mathrm{{ad}}$$ was sufficiently small so that we can use it for heat capacity measurements on helium monolayers in a wide temperature range below 1 K. We found a relatively large excess heat capacity in $$C_\mathrm{{ad}}$$ , which was successfully attributed to atomic tunneling of hydrogen (H) and deuterium (D) between trap centers near oxygen or nitrogen impurities in Nb. The tunnel frequencies of H and D deduced by fitting the data to the tunneling model are consistent with the previous experiments on Nb doped with H or D. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|