Vanishing Phase Stiffness and Fluctuation-Dominated Superconductivity: Evidence for Inter-Band Pairing in UTe$_2$
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arXiv
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| Auteurs principaux: | , , , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866908763811741696 |
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| author | Kamat, Sahas Dans, Jared Saha, Shanta Agterberg, Daniel F. Paglione, Johnpierre Ramshaw, B. J. |
| author_facet | Kamat, Sahas Dans, Jared Saha, Shanta Agterberg, Daniel F. Paglione, Johnpierre Ramshaw, B. J. |
| contents | Superconductivity in three dimensions is almost universally governed by Ginzburg-Landau mean field theory, with critical fluctuations typically confined to within a few percent of the transition temperature ($T_{\rm c}$). We report that the heavy-Fermion superconductor UTe$_2$ exhibits a fluctuation regime that extends over a temperature range as wide as $T_{\rm c}$ itself -- the largest observed for any three-dimensional superconductor. Through ultrasound measurements of the elastic moduli and sound attenuation, we find that UTe$_2$ transitions from a mean-field-like state at ambient pressure to a fluctuation dominated state at higher pressures. This regime is marked by elastic softening and an increase in sound attenuation that onsets well above $T_{\rm c}$, with the attenuation remaining anomalously high deep in the superconducting state. Our analysis shows that these features stem from an extremely low superfluid phase stiffness. This results in a kinetic inductance as high as that of granular aluminum, but achieved in the clean limit. We propose that this exotic state is driven by dominant inter-band pairing mediated by ferromagnetic fluctuations, leading to "local" cooper pairs with a coherence length of only a few lattice constants. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_09138 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Vanishing Phase Stiffness and Fluctuation-Dominated Superconductivity: Evidence for Inter-Band Pairing in UTe$_2$ Kamat, Sahas Dans, Jared Saha, Shanta Agterberg, Daniel F. Paglione, Johnpierre Ramshaw, B. J. Superconductivity Strongly Correlated Electrons Superconductivity in three dimensions is almost universally governed by Ginzburg-Landau mean field theory, with critical fluctuations typically confined to within a few percent of the transition temperature ($T_{\rm c}$). We report that the heavy-Fermion superconductor UTe$_2$ exhibits a fluctuation regime that extends over a temperature range as wide as $T_{\rm c}$ itself -- the largest observed for any three-dimensional superconductor. Through ultrasound measurements of the elastic moduli and sound attenuation, we find that UTe$_2$ transitions from a mean-field-like state at ambient pressure to a fluctuation dominated state at higher pressures. This regime is marked by elastic softening and an increase in sound attenuation that onsets well above $T_{\rm c}$, with the attenuation remaining anomalously high deep in the superconducting state. Our analysis shows that these features stem from an extremely low superfluid phase stiffness. This results in a kinetic inductance as high as that of granular aluminum, but achieved in the clean limit. We propose that this exotic state is driven by dominant inter-band pairing mediated by ferromagnetic fluctuations, leading to "local" cooper pairs with a coherence length of only a few lattice constants. |
| title | Vanishing Phase Stiffness and Fluctuation-Dominated Superconductivity: Evidence for Inter-Band Pairing in UTe$_2$ |
| topic | Superconductivity Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2601.09138 |