Superconductivity in the Locally Noncentrosymmetric Th2Mo2Rh2Si4C by Rational Design.

Locally noncentrosymmetric (LNC) superconductors with broken local inversion symmetry can exhibit exotic properties due to antisymmetric spin-orbit coupling (SOC). A promising strategy to construct LNC superconductors is to incorporate LNC blocks into superconducting lattices. Herein, a complex LNC superconductor, Th2Mo2Rh2Si4C, was designed and successfully synthesized. This compound adopts a unique 22241* structure, in which the superconducting [Mo2Si2C] block loses its out-of-plane mirror symmetry due to being sandwiched between antifluorite-type [Rh2Si2] and fluorite-type [Si2Rh2] layers. Physical property measurements indicate the title compound exhibits bulk superconductivity with a remarkably enhanced upper critical field μ0Hc2(0) of 1.39 T, five times higher than that of the constituent ThMo2Si2C, albeit with a similar transition temperature Tc = 2.1 K. First-principles calculations further reveal a Rashba-type SOC due to the lack of local inversion symmetry, which results in multiple gapped band crossings and significant band splitting near the Fermi level. This work provides a new material platform to study the interplay between superconductivity and Rashba-type SOC and lays a rational path for the exploration of LNC superconductors.