Superconductivity induced by electron doping in the system La1-xMxOBiS2 (M = Ti, Zr, Hf, Th)

TL;DR

This study demonstrates that electron doping through tetravalent substitution in LaOBiS$_2$ induces superconductivity with T$_c$ up to 2.85 K, while hole doping does not produce superconductivity.

Contribution

It introduces a new doping strategy using tetravalent elements to induce superconductivity in LaOBiS$_2$, expanding the understanding of charge doping effects in BiS$_2$-based compounds.

Findings

Electron doping induces superconductivity with T$_c$ up to 2.85 K.

Hole doping via Sr substitution does not induce superconductivity.

Both parent compounds are bad metals, and doping modifies their electronic states.

Abstract

We report a strategy to induce superconductivity in the BiS$_2$-based compound LaOBiS$_2$. Instead of substituting F for O, we increase the charge-carrier density (electron dope) via substitution of tetravalent Th$^{+4}$, Hf$^{+4}$, Zr$^{+4}$, and Ti$^{+4}$ for trivalent La$^{+3}$. It is found that both the LaOBiS$_2$ and ThOBiS$_2$ parent compounds are bad metals and that superconductivity is induced by electron doping with \emph{T$_c$} values of up to 2.85 K. The superconducting and normal states were characterized by electrical resistivity, magnetic susceptibility, and heat capacity measurements. We also demonstrate that reducing the charge-carrier density (hole doping) via substitution of divalent Sr$^{+2}$ for La$^{+3}$ does not induce superconductivity.