Possibility of BCS-BEC crossover in $κ$-type organic superconductors
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arXiv
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| Format: | Preprint |
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2024
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| _version_ | 1866910835306135552 |
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| author | Watanabe, Hiroshi Ikeda, Hiroaki |
| author_facet | Watanabe, Hiroshi Ikeda, Hiroaki |
| contents | The realization of BCS-BEC crossover in superconductors, which smoothly connects Bardeen-Cooper-Schrieffer (BCS) theory with Bose-Einstein Condensation (BEC) in fermion systems, is an intriguing recent topic in strongly correlated electron systems. The organic superconductor $κ$-(BEDT-TTF)$_4$Hg$_{2.89}$Br$_8$ ($κ$-HgBr) under pressure is one of the leading candidates, owing to its unique metallic spin-liquid nature and tunable electron correlation. We theoretically investigate the extended Hubbard model for $κ$-HgBr and discuss the possibility of the BCS-BEC crossover by systematically calculating superconducting correlation function, coherence length, superfluid weight, and chemical potential. Our findings show that the BCS-BEC crossover can be observed when competing phases, such as Mott insulators and charge and/or spin orders, are suppressed by appropriate hole doping. $κ$-HgBr is just the case because both the Mott insulating phase and magnetic orders are absent due to its nonstoichiometric Hg composition and geometrical frustration. We further propose that other $κ$-type organic superconductors could serve as potential candidates of the BCS-BEC crossover if their band fillings and degree of geometrical frustration are systematically tuned. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2411_15510 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Possibility of BCS-BEC crossover in $κ$-type organic superconductors Watanabe, Hiroshi Ikeda, Hiroaki Superconductivity Strongly Correlated Electrons The realization of BCS-BEC crossover in superconductors, which smoothly connects Bardeen-Cooper-Schrieffer (BCS) theory with Bose-Einstein Condensation (BEC) in fermion systems, is an intriguing recent topic in strongly correlated electron systems. The organic superconductor $κ$-(BEDT-TTF)$_4$Hg$_{2.89}$Br$_8$ ($κ$-HgBr) under pressure is one of the leading candidates, owing to its unique metallic spin-liquid nature and tunable electron correlation. We theoretically investigate the extended Hubbard model for $κ$-HgBr and discuss the possibility of the BCS-BEC crossover by systematically calculating superconducting correlation function, coherence length, superfluid weight, and chemical potential. Our findings show that the BCS-BEC crossover can be observed when competing phases, such as Mott insulators and charge and/or spin orders, are suppressed by appropriate hole doping. $κ$-HgBr is just the case because both the Mott insulating phase and magnetic orders are absent due to its nonstoichiometric Hg composition and geometrical frustration. We further propose that other $κ$-type organic superconductors could serve as potential candidates of the BCS-BEC crossover if their band fillings and degree of geometrical frustration are systematically tuned. |
| title | Possibility of BCS-BEC crossover in $κ$-type organic superconductors |
| topic | Superconductivity Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2411.15510 |