Abstract
Surfaces of three-dimensional topological insulators have emerged as one of the most remarkable states of condensed quantum matter where exotic electronic phases of Dirac particles should arise. Here we report on superconductivity in the topological insulator Sb2Te3 with transition to zero resistance induced through a minor tuning of growth chemistry that depletes bulk conduction channels. The depletion shifts Fermi energy towards the Dirac point as witnessed by a factor of 300 reduction of bulk carrier density and by the largest carrier mobility (≳25,000 cm(2) V(-1) s(-1)) found in any topological material. Direct evidence from transport, the unprecedentedly large diamagnetic screening, and the presence of ∼25 meV gaps detected by scanning tunnelling spectroscopy reveal the superconducting condensate to emerge first in surface puddles, with the onset of global phase coherence at ∼9 K. The rich structure of this state lends itself to manipulation via growth conditions and the material parameters such as Fermi velocity and mean free path.
Highlights
Surfaces of three-dimensional topological insulators have emerged as one of the most remarkable states of condensed quantum matter where exotic electronic phases of Dirac particles should arise
In the narrow Te pressure range 1.2oPo1.5 MPa, where superconductivity is found, the bulk hole density obtained from Hall resistivity is reduced by over two orders of magnitude (Fig. 1b, Supplementary Fig. 3 and Supplementary Table 1) to t1018 cm À 3—a finding which should be contrasted with the increased electron density recorded in, for example, superconducting Bi2Se3 doped with Cu
One is the uncovered extreme sensitivity to the growth parameters that reveals an instability to strong correlations, leading to our discovery of superconductivity at ambient pressure and relatively high temperature of B8.6 K
Summary
Surfaces of three-dimensional topological insulators have emerged as one of the most remarkable states of condensed quantum matter where exotic electronic phases of Dirac particles should arise. Unconventional superconductivity involving electron bands with nontrivial topological character has been predicted[1,2,3,4,5] to arise on the surfaces of three-dimensional topological insulators (TIs), where conduction channels host helical Dirac fermions[6,7,8,9,10] that cannot be destroyed by nonmagnetic scattering processes Such topological superconductors are expected to host unusual Majorana modes[1] with special non-Abelian statistics[11] and usher in new approaches to quantum device engineering and materials science. We report that surface superconductivity in the topological material Sb2Te3 with hole-like (p-type) bulk conduction can be induced at a remarkably high temperature by a very minor change in Te vapour pressure during the crystal growth. Notwithstanding presently rudimentary undestanding of the connection between high temperature precursors and Tc itself, our results raise a possibility of engineering even higher transition temperatures through controlled tuning of charge doping during materials’ growth
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