Higher-order topological phases for time-reversal-symmetry breaking superconductivity in UTe$_2$
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866911256513871872 |
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| author | Yamazaki, Yuki Kobayashi, Shingo |
| author_facet | Yamazaki, Yuki Kobayashi, Shingo |
| contents | The recent discovery of heavy-fermion superconductor UTe$_2$ has broadened the possibility of realizing exotic time-reversal-symmetry-breaking superconductivity. However, a comprehensive understanding of the topological phases in the superconducting states of UTe$_2$ is still lacking. Here, we present an exhaustive classification of topological phases for all time-reversal symmetry breaking pairing symmetries of UTe$_2$. Using the K theoretical classification approach, we uncover that 25 out of 36 possible pairing states are classified as higher-order topological phases, with some demonstrating hybrid-order topology through an intricate interplay of hinge and corner states. Furthermore, under the weak-coupling condition of the pair potentials, the possible pairing symmetries are constrained to $B_{ju} + i B_{ku}$, $A_{u} + i B_{j u}$, and $B_{j g} + iA_u$ ($j,k = 1,2,3$; $j \neq k$), where these symbols denote the irreducible representations of the point group $D_{2h}$. For these pairing states, the topological invariants are related to the Fermi surface topology via the Fermi-surface formula, enabling us to systematically diagnose higher-order topological phases. Using a tight-binding model, we demonstrate the higher-order topological phases of the mixed-parity $A_u + iB_{1g}$ superconductors, where the second-order and hybrid-order topological phases emerge as the number of Fermi surfaces enclosing the time-reversal invariant momentum evolves from two to four. The findings suggest that UTe$_2$ serves as a compelling platform for exploring higher-order topological superconductors with diverse topological surface states. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2504_01584 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Higher-order topological phases for time-reversal-symmetry breaking superconductivity in UTe$_2$ Yamazaki, Yuki Kobayashi, Shingo Superconductivity The recent discovery of heavy-fermion superconductor UTe$_2$ has broadened the possibility of realizing exotic time-reversal-symmetry-breaking superconductivity. However, a comprehensive understanding of the topological phases in the superconducting states of UTe$_2$ is still lacking. Here, we present an exhaustive classification of topological phases for all time-reversal symmetry breaking pairing symmetries of UTe$_2$. Using the K theoretical classification approach, we uncover that 25 out of 36 possible pairing states are classified as higher-order topological phases, with some demonstrating hybrid-order topology through an intricate interplay of hinge and corner states. Furthermore, under the weak-coupling condition of the pair potentials, the possible pairing symmetries are constrained to $B_{ju} + i B_{ku}$, $A_{u} + i B_{j u}$, and $B_{j g} + iA_u$ ($j,k = 1,2,3$; $j \neq k$), where these symbols denote the irreducible representations of the point group $D_{2h}$. For these pairing states, the topological invariants are related to the Fermi surface topology via the Fermi-surface formula, enabling us to systematically diagnose higher-order topological phases. Using a tight-binding model, we demonstrate the higher-order topological phases of the mixed-parity $A_u + iB_{1g}$ superconductors, where the second-order and hybrid-order topological phases emerge as the number of Fermi surfaces enclosing the time-reversal invariant momentum evolves from two to four. The findings suggest that UTe$_2$ serves as a compelling platform for exploring higher-order topological superconductors with diverse topological surface states. |
| title | Higher-order topological phases for time-reversal-symmetry breaking superconductivity in UTe$_2$ |
| topic | Superconductivity |
| url | https://arxiv.org/abs/2504.01584 |