Experimental evidence of anomalously large superconducting gap on topological surface state of $\beta$-$\mathbf{B}{\mathbf{i}}_2\mathbf{Pd}$ film

Abstract

Connate topological superconductor (TSC) combines topological surface states with nodeless superconductivity in a single material, achieving effective $p$-wave pairing without interface complication. By combining angle-resolved photoemission spectroscopy and $in$-$situ$ molecular beam epitaxy, we studied the momentum-resolved superconductivity in $\beta$-$\mathrm{B}{\mathrm{i}}_2\mathrm{Pd}$ film. We found that the superconducting gap of topological surface state (${\Delta }_{TSS}\sim$ 3.8 meV) is anomalously enhanced from its bulk value (${\Delta }_b\sim$ 0.8 meV). The ratio of $2{\Delta }_{TSS}/k_B{T}_c\sim 14.2$, is substantially larger than the BCS value. By measuring $\beta$-$\mathrm{B}{\mathrm{i}}_2\mathrm{Pd}$ bulk single crystal as a comparison, we clearly observed the upward-shift of chemical potential in the film. In addition, a concomitant increasing of surface weight on the topological surface state was revealed by our first principle calculation, suggesting that the Dirac-fermion-mediated parity mixing may cause this anomalous superconducting enhancement. Our results establish $\beta$-$\mathrm{B}{\mathrm{i}}_2\mathrm{Pd}$ film as a unique case of connate TSCs with a highly enhanced topological superconducting gap, which may stabilize Majorana zero modes at a higher temperature.

arXiv comment16 pages, 8 figures

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Cited by in corpus (9)

• Observation of topological electronic structure in quasi-1D superconductor TaSe3
• Detecting Majorana Zero Modes via Strong Field Dynamics
• Correlation-corrected band topology and topological surface states in iron-based superconductors
• Prediction of superconductivity and topological aspects in single-layer $\beta$-Bi${}_2$Pd
• Large spin to charge conversion in topological superconductor \b{eta}-PdBi2 at room temperature
• Topological superconductor candidates PdBi${}_2$Te${}_4$ and PdBi${}_2$Te${}_5$ from a generic ab initio strategy
• Anomalous superconducting proximity effect of planar Pb-RhPb2 heterojunctions in the clean limit
• Direct observation of the surface superconducting gap in the topological superconductor candidate β-PdBi2
• Self-regulated growth of candidate topological superconducting parkerite by molecular beam epitaxy