Superconductivity in layered Zintl phase LiSn2As2

We report the superconductivity in the layered Zintl phase LiSn$_2$As$_2$, which is isostructural to NaSn$_2$As$_2$ and has a transition temperature ($T_{\mathrm{c}}$) of 1.6 K. Despite similar $T_{\mathrm{c}}$ and Debye temperatures, substituting of Na with Li considerably increases the upper critical field. Based on a systematically comparation of Sn$_4$As$_3$, NaSnAs, NaSn$_2$As$_2$,Na$_{1-x}$Sn$_2$P$_2$, SrSn$_2$As$_2$, and LiSn$_2$As$_2$, we propose that carrier doping, intimately related to the formation of lone-pair electrons, controls superconductivity in layered SnAs-based compounds rather than chemical pressure. The current findings provide a thorough and comprehensive understanding of Sn-based Zintl phase.