# Enhanced Electron–Phonon Coupling of Superconductivity in Indium-Doped Topological Crystalline Insulator SnTe

## TL;DR

This paper studies how doping SnTe with indium enhances superconductivity through stronger electron-phonon coupling.

## Contribution

The study reveals a tunable superconducting system in Sn1−xInxTe with controllable coupling strength.

## Key findings

- Superconducting transition temperature increases with indium concentration, reaching 4.7 K at x = 0.5.
- Electron–phonon coupling constant increases while Debye temperature decreases with doping.
- Normal-state resistivity evolves from Fermi-liquid to non-Fermi-liquid behavior with increasing In content.

## Abstract

Indium-doped SnTe (Sn1−xInxTe) provides a model platform for exploring the emergence of superconductivity within a topological crystalline insulator. Here, we present a systematic investigation of the structural, transport, and thermodynamic properties of high-quality single crystals with 0.0 ≤ x ≤ 0.5. All compositions up to x = 0.4 form a single-phase cubic structure, enabling a controlled study of the superconducting state. Electrical resistivity and specific heat measurements reveal a bulk, fully gapped s-wave superconducting phase whose transition temperature increases monotonically with In concentration, reaching Tc ≈ 4.7 K at x = 0.5. Analysis of the electronic specific heat and McMillan formalism shows that the electron–phonon coupling constant λel-ph systematically increases with doping, while the Debye temperature systematically decreases, resulting in the lattice softening. This behavior, together with the observed evolution of the normal-state resistivity exponent from Fermi-liquid (n ≈ 2.04) toward non-Fermi-liquid values (n ≈ 1.72), demonstrates a clear crossover from weak to strong interaction with increasing In content. These results establish Sn1−xInxTe as a tunable superconducting system in which coupling strength can be continuously controlled, offering a promising platform for future studies on the interplay between phonon-mediated superconductivity and crystalline topological band structure.