Evolution of electronic states and emergence of superconductivity in the polar semiconductor GeTe by doping valence-skipping In

Abstract

GeTe is a chemically simple IV-VI semiconductor which bears a rich plethora of different physical properties induced by doping and external stimuli. These include, among others, ferromagnetism, ferroelectricity, phase-change memory functionality, and comparably large thermoelectric figure of merits. Here we report a superconductor - semiconductor - superconductor transition controlled by finely-tuned In doping. Our results moreover show the existence of a critical doping concentration around $x=0.12$ in Ge${}_{1-x}$In${}_x$Te, where various properties take either an extremum or change their characters: The structure changes from polarly-rhombohedral to cubic, the resistivity sharply increases by orders of magnitude, the type of charge carriers changes from holes to electrons, and the density of states diminishes at the dawn of an emerging superconducting phase. By core-level photoemission spectroscopy we find indications of a change in the In-valence state from In${}^{3+}$ to In${}^{1+}$ with increasing $x$, suggesting that this system is a new promising playground to probe valence fluctuations and their possible impact on superconductivity.

arXiv commentMain text (4 Figures) + Supplement(9 Figures)

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Cited by in corpus (6)

• Superconducting properties of high-entropy-alloy tellurides M-Te (M: Ag, In, Cd, Sn, Sb, Pb, Bi) with a NaCl-type structure
• Superconducting ground state study of valence skip compound AgSnSe${}_2$
• Reentrant proximity-induced superconductivity for GeTe semimetal
• Enhancement of superconductivity and its relation to lattice expansion in InTe
• Probing Mixed Valence States by Nuclear Spin-Spin Relaxation Time Measurements
• Theory of ab initio downfolding with arbitrary range electron-phonon coupling