Emergent surface superconductivity in the topological insulator Sb2Te3

Area of Science:

• Condensed matter physics
• Materials science
• Quantum materials

Background:

• Topological insulators (TIs) are exotic quantum materials hosting unique electronic properties.
• Their surfaces are predicted to exhibit Dirac fermion states, crucial for novel electronic phases.

Purpose of the Study:

• To investigate superconductivity in the three-dimensional topological insulator antimony telluride (Sb2Te3).
• To understand the role of surface states and bulk carrier depletion in inducing superconductivity.

Main Methods:

• Chemical tuning of growth conditions for Sb2Te3.
• Transport measurements to assess electrical resistance and carrier properties.
• Scanning tunneling spectroscopy (STS) to probe electronic energy gaps.
• Magnetic susceptibility measurements to detect diamagnetic screening.

Main Results:

• Superconductivity induced in Sb2Te3 via minor chemical tuning, leading to zero resistance.
• Significant depletion of bulk carriers (factor of 300 reduction) and enhanced carrier mobility (>25,000 cm2 V−1 s−1).
• Evidence of superconductivity originating in surface puddles, with global phase coherence onset at ~9 K.
• Observation of ~25 meV energy gaps using STS.

Conclusions:

• Superconductivity can be controllably induced in topological insulators like Sb2Te3.
• Surface states play a critical role in the emergence of superconductivity in these materials.
• The superconducting state in Sb2Te3 is tunable via growth conditions and material parameters.