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arXiv 1802.06119cond-mat.supr-concond-mat.str-el
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笼型化合物La $Tr_{2}$ Al $_{20}$(其中$Tr$ = Ti,V,Nb,Ta)的超导电性

Superconductivity in Cage Compounds La$Tr_{2}$Al$_{20}$ with $Tr$ = Ti, V, Nb, and Ta

Akira Yamada, Ryuji Higashinaka, Tatsuma D. Matsuda, Yuji Aoki

摘要:

电阻率,磁化率,和比热的La $Tr_{2}$铝$_{20}$($Tr$ = Ti,V,Nb,Ta)单晶的测量表明,这四个化合物表现出弱耦合超导转变温度$T_{\rm c}$ = 0.46,0.15,1.05,和1.03 K,分别。LaTi $_{2}$ Al $_{20}$最有可能是I型超导体,这在金属间化合物中是非常罕见的。单晶X-射线衍射表明铝离子(16 $c$网站)的铝$_{16}$笼上的“嘎嘎作响”的非谐大振幅振荡,而没有这样的功能,建议为笼中心的La离子。利用参数$d_{\rm GFS}$量化笼中心离子的“客体自由空间”,我们证明了掺杂的$RTr_{2}$ Al $_{20}$超导体可分为两类,即,(A)$d_{\rm GFS} \ne 0$和$T_{\rm c}$与$d_{\rm GFS}$相关,(B)$d_{\rm GFS} \simeq 0$和$T_{\rm c}$似乎受其他因素控制。

英文摘要:

Electrical resistivity, magnetic susceptibility, and specific heat measurements on single crystals of La$Tr_{2}$Al$_{20}$ ($Tr$ = Ti, V, Nb, and Ta) revealed that these four compounds exhibit weak-coupling superconductivity with transition temperatures $T_{\rm c}$ = 0.46, 0.15, 1.05, and 1.03 K, respectively. LaTi$_{2}$Al$_{20}$ is most probably a type-I superconductor, which is quite rare among intermetallic compounds. Single-crystal X-ray diffraction suggests "rattling" anharmonic large-amplitude oscillations of Al ions (16$c$ site) on the Al$_{16}$ cage, while no such feature is suggested for the cage-center La ion. Using a parameter $d_{\rm GFS}$ quantifying the "guest free space" of the cage-center ion, we demonstrate that nonmagnetic $RTr_{2}$Al$_{20}$ superconductors are classified into two groups, i.e., (A) $d_{\rm GFS} \ne 0$ and $T_{\rm c}$ correlates with $d_{\rm GFS}$, and (B) $d_{\rm GFS} \simeq 0$ and $T_{\rm c}$ seems to be governed by other factors.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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