@article{oai:kyutech.repo.nii.ac.jp:00005911,
 author = {Mito, Masaki and 美藤, 正樹 and Kitamura, Yuichiro and Tajiri, Takayuki and Nakamura, Kazuma and 中村, 和磨 and Shiraishi, Ryo and Ogata, Kazuma and Deguchi, Hiroyuki and 出口, 博之 and Yamaguchi, Tomiko and 山口, 富子 and Takeshita, Nao and Nishizaki, Terukazu and Edalati, Kaveh and Horita, Zenji and 堀田, 善治},
 issue = {12},
 journal = {Journal of Applied Physics},
 month = {Mar},
 note = {We study the effects of hydrostatic pressure (HP) compression on the superconducting transition of severely strained Nb samples, whose grain sizes are reduced to the submicrometer level. Engineered granularity by high-pressure torsion (HPT) treatment changes the strength of coupling between submicrometer-scale grains and introduces lattice strain. We attempt to utilize the initially accumulated shear strain in the starting material for increasing the superconducting transition temperature Tc under HP compression. The HP effects on non-strained Nb have already been investigated in the pressure regime over 100 GPa by Struzhkin et al. [Phys. Rev. Lett. 79, 4262 (1997)], and Tc reportedly exhibited an increase from 9.2 to 9.9 K at approximately 10 GPa. (1) Slightly strained Nb in the HPT treatment exhibits the increase in Tc under HP due to the strengthening of the intergrain coupling, so the pressure scale of the pressure response observed by Struzhkin et al. is reduced to approximately one-seventh at the maximum. (2) Prominently strained Nb in the HPT treatment exhibits the increase in Tc under HP due to a reduction in structural symmetry at the unit-cell level: In a Nb sample subjected to HPT (6 GPa, 10 revolutions), Tc exceeds 9.9 K at approximately 2 GPa. According to our first-principle calculations, the reduction in the structural symmetry affords an increase in the density of states at the Fermi energy, thereby yielding a prominent increase in Tc at low pressures.},
 pages = {125901-1--125901-13},
 title = {Hydrostatic pressure effects on superconducting transition of nanostructured niobium highly strained by high-pressure torsion},
 volume = {125},
 year = {2019},
 yomi = {ミトウ, マサキ and ナカムラ, カズマ and デグチ, ヒロユキ and ヤマグチ, トミコ and ホリタ, ゼンジ}
}