Frontier Research Center, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan.
Phys Rev Lett. 2011 Jun 10;106(23):237001. doi: 10.1103/PhysRevLett.106.237001. Epub 2011 Jun 8.
LaCo(2)B(2) with a ThCr(2)Si(2)-type (so-called "122") structure composed of alternately stacked La and CoB layers exhibits metallic electrical conductivity and Pauli paramagnetic behavior down to 2 K. Bulk superconductivity with a T(c) of ∼4 K emerges upon substituting with dopant elements, i.e., isovalent substitution to form (La(1-x)Y(x))Co(2)B(2), or aliovalent substitution to form La(Co(1-x)Fe(x))(2)B(2). According to the density functional theory calculations, highly covalent bonding between Co 3d dominating the Fermi level and B 2p levels deeper than the Fermi level removes magnetic ordering from Co 3d electrons even in the undoped samples. This is a first Co-based superconductor among the 122-type family.
LaCo(2)B(2) 具有 ThCr(2)Si(2)型（所谓的“122”型）结构，由交替堆叠的 La 和 CoB 层组成，在 2 K 以下表现出金属导电性和 Pauli 顺磁性。通过掺杂元素替代形成（La(1-x)Y(x))Co(2)B(2)（等摩尔替代），或者形成 La(Co(1-x)Fe(x))(2)B(2)（不等摩尔替代），会出现具有 T(c)约为 4 K 的体超导性。根据密度泛函理论计算，费米能级附近主导的 Co 3d 与费米能级以下更深的 B 2p 之间的高度共价键，即使在未掺杂样品中，也会消除 Co 3d 电子的磁有序。这是 122 型家族中第一个基于 Co 的超导体。
