Hydrostatic pressure effects on superconducting transition of nanostructured niobium highly strained by high-pressure torsion
Hydrostatic pressure effects on superconducting transition of nanostructured niobium highly strained by high-pressure torsion
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DOI：
10.1063/1.5083094
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发表时间：
2019-03-28
影响因子：
3.2
通讯作者：
Horita, Zenji
中科院分区：
文献类型：
--
作者：
Mito, Masaki;Kitamura, Yuichiro;Horita, Zenji
我们研究了静液压压缩（HP）压缩对严重紧张的NB样品超导过渡的影响，其晶粒尺寸降低到亚微米水平。通过高压扭转（HPT）处理进行工程粒度，改变了亚微米尺寸晶粒之间的耦合强度，并引入了晶格菌株。我们尝试利用起始材料中最初积累的剪切应变来增加超导过渡温度T-C。在HP压缩下。 Struzhkin等人已经在100 GPA的压力状态下已经研究了对非受阻NB的HP影响。 [物理。莱特牧师。 79，4262（1997）]和T-C。据报道，大约10 GPA的增长率从9.2增加到9.9 K。 （1）HPT治疗中NB略有紧张的NB表现出T-C的增加。在HP下，由于粒间耦合的增强，因此Struzhkin等人观察到的压力响应的压力尺度。在最大值下减少至大约17。 （2）HPT治疗中突出的NB突然紧张的NB表现出T-C的增加。在HP下，由于单位细胞水平下的结构对称性降低：在接受HPT的NB样品中（6 GPA，10转），T-C。在大约2 GPA时超过9.9 K。根据我们的第一原则计算，结构对称性的减少使费米能量处的状态密度增加，从而导致T-C显着增加。在低压下。根据AIP出版的许可发布
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 T-c. 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 T-c. 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 T-c. 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 T-c. 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), T-c. 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 T-c. at low pressures. Published under license by AIP Publishing