Magnetic penetration depth in topological superconductors: Effect of Majorana surface states and application for UTe$_2$
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| Format: | Preprint |
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2025
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| _version_ | 1866912946733449216 |
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| author | Akuzawa, Kazuki Tei, Jushin Ohashi, Ryoi Fujimoto, Satoshi Mizushima, Takeshi |
| author_facet | Akuzawa, Kazuki Tei, Jushin Ohashi, Ryoi Fujimoto, Satoshi Mizushima, Takeshi |
| contents | In this study, we examine how orbital degrees of freedom and Majorana surface states influence the magnetic penetration depth in the superconductor UTe$_2$. Using a two-orbital model, we analyze pairing states belonging to the irreducible representations of the $D_{2h}$ crystal symmetry: $A_u$, $B_{1u}$, $B_{2u}$, and $B_{3u}$. For bulk nodal states such as $B_{2u}$, we find that the penetration depth for screening currents along the antinodal direction and the cylindrical axis scales as $T^2$, in strong contrast to the conventional $T^4$ law. This behavior originates from quasiparticles near the point nodes contributing to the interorbital paramagnetic current. We further show that Majorana surface states can dominate the low-temperature response. The fully gapped $A_u$ state hosts Majorana cones, which produce a $T^3$ dependence of the penetration depth when the ratio of penetration depth to coherence length ($κ$) is small. In contrast, the other pairing states exhibit Majorana Fermi arcs: the exponent is $n=2$ along the dispersive direction, while along the dispersionless direction it depends on whether the arcs terminate at endpoints. The exponent $n=2$ in the dispersive direction is robust, while it in the dispersionless direction relies on the presence or absence of the endpoints of the arcs and deviates from $n=2$ when endpoints are absent. Our results demonstrate that penetration-depth measurements provide a direct probe of Majorana surface states in low-$κ$ superconductors. For larger $κ$, the surface contribution becomes negligible and the temperature dependence is governed by bulk quasiparticles. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2509_18441 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Magnetic penetration depth in topological superconductors: Effect of Majorana surface states and application for UTe$_2$ Akuzawa, Kazuki Tei, Jushin Ohashi, Ryoi Fujimoto, Satoshi Mizushima, Takeshi Superconductivity In this study, we examine how orbital degrees of freedom and Majorana surface states influence the magnetic penetration depth in the superconductor UTe$_2$. Using a two-orbital model, we analyze pairing states belonging to the irreducible representations of the $D_{2h}$ crystal symmetry: $A_u$, $B_{1u}$, $B_{2u}$, and $B_{3u}$. For bulk nodal states such as $B_{2u}$, we find that the penetration depth for screening currents along the antinodal direction and the cylindrical axis scales as $T^2$, in strong contrast to the conventional $T^4$ law. This behavior originates from quasiparticles near the point nodes contributing to the interorbital paramagnetic current. We further show that Majorana surface states can dominate the low-temperature response. The fully gapped $A_u$ state hosts Majorana cones, which produce a $T^3$ dependence of the penetration depth when the ratio of penetration depth to coherence length ($κ$) is small. In contrast, the other pairing states exhibit Majorana Fermi arcs: the exponent is $n=2$ along the dispersive direction, while along the dispersionless direction it depends on whether the arcs terminate at endpoints. The exponent $n=2$ in the dispersive direction is robust, while it in the dispersionless direction relies on the presence or absence of the endpoints of the arcs and deviates from $n=2$ when endpoints are absent. Our results demonstrate that penetration-depth measurements provide a direct probe of Majorana surface states in low-$κ$ superconductors. For larger $κ$, the surface contribution becomes negligible and the temperature dependence is governed by bulk quasiparticles. |
| title | Magnetic penetration depth in topological superconductors: Effect of Majorana surface states and application for UTe$_2$ |
| topic | Superconductivity |
| url | https://arxiv.org/abs/2509.18441 |