Experimental evidence of anomalously large superconducting gap on topological surface state of $β$-$\rm\mathbf{Bi_2Pd}$ film

J. -Y. Guan; L. -Y. Kong; L. -Q. Zhou; Y. -G. Zhong; H. Li; H. -J. Liu; C. -Y. Tang; D. -Y. Yan; F. -Z. Yang; Y. -B. Huang; Y. -G. Shi; T. Qian; H. -M. Weng; Y. -J. Sun; H. Ding

doi:10.1016/j.scib.2019.07.019

paper

Experimental evidence of anomalously large superconducting gap on topological surface state of $β$ - $B i_{2} Pd$ film

arXiv:1904.11638 · doi:10.1016/j.scib.2019.07.019

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 $in$ - $s i t u$ molecular beam epitaxy, we studied the momentum-resolved superconductivity in $β$ - $B i_{2} Pd$ film. We found that the superconducting gap of topological surface state ( $Δ_{T S S} \sim$ 3.8 meV) is anomalously enhanced from its bulk value ( $Δ_{b} \sim$ 0.8 meV). The ratio of $2 Δ_{T S S} / k_{B} T_{c} \sim 14.2$ , is substantially larger than the BCS value. By measuring $β$ - $B i_{2} Pd$ 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 $β$ - $B i_{2} Pd$ 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.

16 pages, 8 figures

Experimental evidence of anomalously large superconducting gap on topological surface state of β-Bi2​Pd film

Abstract

Experimental evidence of anomalously large superconducting gap on topological surface state of $β$ - $B i_{2} Pd$ film