Evidence for Multiband Gapless Superconductivity in the Topological Superconductor Candidate 4Hb-TaS_{2}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• 4Hb-TaS_{2} is a transition-metal dichalcogenide material.
• It has been proposed as a topological superconductor candidate.
• Understanding its superconducting properties is crucial for exploring topological superconductivity.

Purpose of the Study:

• To investigate the superconducting state of 4Hb-TaS_{2} using ultra-low-temperature thermal conductivity measurements.
• To determine the nature of the superconducting gap and the presence of nodes.
• To explore the possibility of multiple superconducting gaps.

Main Methods:

• Ultra-low-temperature thermal conductivity measurements were performed on single crystals of 4Hb-TaS_{2}.
• Measurements were conducted in both zero magnetic field and varying magnetic field strengths.
• Analysis focused on the field dependence of the residual linear term of thermal conductivity (κ_{0}/T).

Main Results:

• A small residual linear term (κ_{0}/T) was observed in zero field, indicating a residual density of states in the superconducting state.
• The slow field dependence of κ_{0}/T at low fields suggests the absence of nodes in the superconducting gap.
• An S-shaped field dependence across the full field range points towards multiple superconducting gaps.

Conclusions:

• The results provide evidence for multiband gapless superconductivity in 4Hb-TaS_{2}.
• The observed residual density of states originates from gapless Fermi surfaces.
• These findings contribute to the understanding of topological superconductor candidates.