Full superconducting gap in the candidate topological superconductor In1−xPbxTe for x=0.2

High-pressure synthesis techniques have allowed for the growth of samples on the indium-rich side of (Pb,In)Te, which have increased superconducting transition temperatures compared to lead-rich compounds. Here, we present measurements of the temperature dependence of the London penetration depth Δλ(T) in the compound In_0.8Pb_0.2Te, which shows a bulk T_c,onset of ~ 4.75 K. The results indicate fully gapped BCS-like behavior, ruling out odd-parity topologically nontrivial A_2u, pairing, however, odd-parity A_1u, pairing is still possible. Critical field values measured below 1 K and other superconducting parameters are also presented.