Versatile electronic states in epitaxial thin films of (Sn-Pb-In)Te: From topological crystalline insulator and polar semimetal to superconductor

Abstract

Epitaxial thin films of (SnxPb1−x)1−yInyTe were successfully grown by molecular-beam epitaxy in a broad range of compositions (0≤x≤1, 0≤y≤0.23). We investigated electronic phases of the films by the measurements of electrical transport and optical second-harmonic generation. In this system, one can control the inversion of the band gap, the electric polarization that breaks the inversion symmetry, and the Fermi-level position by tuning the Pb/Sn ratio and In composition. A plethora of topological electronic phases is expected to emerge, such as the topological crystalline insulator, the topological semimetal, and superconductivity. For the samples with large Sn compositions (x>0.5), hole density increases with In composition (y), which results in the appearance of superconductivity. On the other hand, for those with small Sn compositions (x<0.5), an increase in In composition reduces the hole density and changes the carrier type from p type to n type. In a narrow region centered at (x,y)=(0.16,0.07) where the n-type carriers are slightly doped, charge transport with high mobility exceeding 5000cm2V–1s–1 shows up, representing the possible semimetal states. In those samples, the optical second-harmonic generation measurement showing the breaking of inversion symmetry along the out-of-plane [111] direction, which is a necessary condition for the emergence of the polar semimetal state. The thin films of (SnxPb1−x)1−yInyTe material systems with a variety of electronic states would become a promising materials platform for the exploration of novel quantum phenomena.

Source-reported materials — not catalogue approval

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