Issue 1, 2024

Two-gap topological superconductor LaB2 with high Tc = 30 K

Abstract

Since two gap superconductivity was discovered in MgB2, research on multigap superconductors has attracted increasing attention because of its intriguing fundamental physics. In MgB2, the Mg atom donates two electrons to the borophene layer, resulting in a stronger gap from the σ band and a weaker gap from the π bond. First-principles calculations demonstrate that the two gap anisotropic superconductivity strongly enhances the transition temperature of MgB2 in comparison with that given by the isotropic model. In this work, we report a three-band (B-σ, B-π, and La-d) two-gap superconductor LaB2 with very high Tc = 30 K by solving the fully anisotropic Migdal–Eliashberg equation. Because of the σ and π–d hybridization on the Fermi surface, the electron–phonon coupling constant λ = 1.5 is significantly larger than the λ = 0.7 of MgB2. Our work paves a new route to enhance the electron–phonon coupling strength of multigap superconductors with d orbitals. On the other hand, our Image ID:d3nh00249g-t1.gif analysis reveals that LaB2 belongs to the weak topological semimetal category, leading to a possible topological superconductor with the highest Tc to date. Moreover, upon applying pressure and/or doping, the topology is tunable between weak and strong with Tc varying from 15 to 30 K, opening up a flexible platform for manipulating topological superconductors.

Graphical abstract: Two-gap topological superconductor LaB2 with high Tc = 30 K

Supplementary files

Article information

Article type
Communication
Submitted
16 Jun 2023
Accepted
19 Oct 2023
First published
08 Nov 2023
This article is Open Access
Creative Commons BY-NC license

Nanoscale Horiz., 2024,9, 148-155

Two-gap topological superconductor LaB2 with high Tc = 30 K

C. Chen, Y. Lan, A. Huang and H. Jeng, Nanoscale Horiz., 2024, 9, 148 DOI: 10.1039/D3NH00249G

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