Apparent double-$T_c$ from a single BKT transition in anisotropic phase-only models
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arXiv
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| Autores principales: | , |
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| Formato: | Preprint |
| Publicado: |
2026
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| _version_ | 1866910207975620608 |
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| author | Cai, Pei-Yuan Zhou, Yi |
| author_facet | Cai, Pei-Yuan Zhou, Yi |
| contents | Transport experiments on two-dimensional superconductors often yield direction-dependent transition temperatures, raising the question of whether such a ``double-$T_c$'' reflects a true thermodynamic splitting or a transport artifact. To establish a baseline, we study a minimal anisotropic phase-only Josephson-junction array in equilibrium and under resistively shunted junction dynamics with fluctuating twist boundary conditions. The equilibrium model exhibits a single Berezinskii--Kosterlitz--Thouless (BKT) transition. Out of equilibrium, anisotropic Josephson couplings and anisotropic dissipation reshape the linear $R$--$T$ curves in a finite-size, finite-current crossover regime, so that curve-shape criteria such as Halperin--Nelson fits and fixed-resistance thresholds yield an apparent double-$T_c$. In contrast, critical-scaling criteria -- the universal exponent $α=3$ and dynamic finite-size scaling -- remain consistent with the single $T_{\mathrm{BKT}}$. A robust splitting that persists in the nonlinear critical scaling, such as that recently reported at KTaO$_3$ interfaces, therefore points to physics beyond this clean anisotropic baseline. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_10226 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Apparent double-$T_c$ from a single BKT transition in anisotropic phase-only models Cai, Pei-Yuan Zhou, Yi Superconductivity Statistical Mechanics Strongly Correlated Electrons Transport experiments on two-dimensional superconductors often yield direction-dependent transition temperatures, raising the question of whether such a ``double-$T_c$'' reflects a true thermodynamic splitting or a transport artifact. To establish a baseline, we study a minimal anisotropic phase-only Josephson-junction array in equilibrium and under resistively shunted junction dynamics with fluctuating twist boundary conditions. The equilibrium model exhibits a single Berezinskii--Kosterlitz--Thouless (BKT) transition. Out of equilibrium, anisotropic Josephson couplings and anisotropic dissipation reshape the linear $R$--$T$ curves in a finite-size, finite-current crossover regime, so that curve-shape criteria such as Halperin--Nelson fits and fixed-resistance thresholds yield an apparent double-$T_c$. In contrast, critical-scaling criteria -- the universal exponent $α=3$ and dynamic finite-size scaling -- remain consistent with the single $T_{\mathrm{BKT}}$. A robust splitting that persists in the nonlinear critical scaling, such as that recently reported at KTaO$_3$ interfaces, therefore points to physics beyond this clean anisotropic baseline. |
| title | Apparent double-$T_c$ from a single BKT transition in anisotropic phase-only models |
| topic | Superconductivity Statistical Mechanics Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2605.10226 |