Superconductivity Mediated by Nematic Fluctuations in Tetragonal $\textrm{Fe}\textrm{Se}_{1-x}\textrm{S}_{x}$
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2024
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| author | Nag, Pranab Kumar Scott, Kirsty de Carvalho, Vanuildo S. Byland, Journey K. Yang, Xinze Walker, Morgan Greenberg, Aaron G. Klavins, Peter Miranda, Eduardo Gozar, Adrian Taufour, Valentin Fernandes, Rafael M. Neto, Eduardo H. da Silva |
| author_facet | Nag, Pranab Kumar Scott, Kirsty de Carvalho, Vanuildo S. Byland, Journey K. Yang, Xinze Walker, Morgan Greenberg, Aaron G. Klavins, Peter Miranda, Eduardo Gozar, Adrian Taufour, Valentin Fernandes, Rafael M. Neto, Eduardo H. da Silva |
| contents | Nematic phases, where electrons in a solid spontaneously break rotational symmetry while preserving the translational symmetry, exist in several families of unconventional superconductors [1, 2]. Although superconductivity mediated by nematic fluctuations is well established theoretically [3-7], it has yet to be unambiguously identified experimentally [8, 9]. A major challenge is that nematicity is often intertwined with other degrees of freedom, such as magnetism and charge order. The FeSe$_{1-x}$S$_x$ family of iron based superconductors provides a unique opportunity to explore this concept, as it features an isolated nematic phase that can be suppressed by sulfur substitution at a quantum critical point (QCP) near $x_c = 0.17$, where nematic fluctuations are the largest [10-12]. Here, we performed scanning tunneling spectroscopy measurements to visualize Boguliubov quasiparticle interference patterns, from which we determined the momentum structure of the superconducting gap near the Brillouin zone $Γ$ point of FeSe$_{0.81}$S$_{0.19}$. The results reveal an anisotropic, near nodal gap with minima that are $45^\circ$ rotated with respect to the Fe-Fe direction, characteristic of a nematic pairing interaction, contrary to the usual isotropic gaps due to spin mediated pairing in other tetragonal Fe-based superconductors. The results are also in contrast with pristine FeSe, where the pairing is mediated by spin fluctuations and the gap minima are aligned with the Fe-Fe direction. Therefore, the measured gap structure demonstrates not only a fundamental change of the pairing mechanism across the phase diagram of FeSe$_{1-x}$S$_x$, but it also indicates the existence of superconductivity mediated by nematic fluctuations in FeSe$_{0.81}$S$_{0.19}$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2403_00615 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Superconductivity Mediated by Nematic Fluctuations in Tetragonal $\textrm{Fe}\textrm{Se}_{1-x}\textrm{S}_{x}$ Nag, Pranab Kumar Scott, Kirsty de Carvalho, Vanuildo S. Byland, Journey K. Yang, Xinze Walker, Morgan Greenberg, Aaron G. Klavins, Peter Miranda, Eduardo Gozar, Adrian Taufour, Valentin Fernandes, Rafael M. Neto, Eduardo H. da Silva Superconductivity Strongly Correlated Electrons Nematic phases, where electrons in a solid spontaneously break rotational symmetry while preserving the translational symmetry, exist in several families of unconventional superconductors [1, 2]. Although superconductivity mediated by nematic fluctuations is well established theoretically [3-7], it has yet to be unambiguously identified experimentally [8, 9]. A major challenge is that nematicity is often intertwined with other degrees of freedom, such as magnetism and charge order. The FeSe$_{1-x}$S$_x$ family of iron based superconductors provides a unique opportunity to explore this concept, as it features an isolated nematic phase that can be suppressed by sulfur substitution at a quantum critical point (QCP) near $x_c = 0.17$, where nematic fluctuations are the largest [10-12]. Here, we performed scanning tunneling spectroscopy measurements to visualize Boguliubov quasiparticle interference patterns, from which we determined the momentum structure of the superconducting gap near the Brillouin zone $Γ$ point of FeSe$_{0.81}$S$_{0.19}$. The results reveal an anisotropic, near nodal gap with minima that are $45^\circ$ rotated with respect to the Fe-Fe direction, characteristic of a nematic pairing interaction, contrary to the usual isotropic gaps due to spin mediated pairing in other tetragonal Fe-based superconductors. The results are also in contrast with pristine FeSe, where the pairing is mediated by spin fluctuations and the gap minima are aligned with the Fe-Fe direction. Therefore, the measured gap structure demonstrates not only a fundamental change of the pairing mechanism across the phase diagram of FeSe$_{1-x}$S$_x$, but it also indicates the existence of superconductivity mediated by nematic fluctuations in FeSe$_{0.81}$S$_{0.19}$. |
| title | Superconductivity Mediated by Nematic Fluctuations in Tetragonal $\textrm{Fe}\textrm{Se}_{1-x}\textrm{S}_{x}$ |
| topic | Superconductivity Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2403.00615 |