Tian Shang, Yuting Wang, Bochen Yu, Keqi Xia, Darek J. Gawryluk, Yang Xu, Qingfeng Zhan, Jianzhou Zhao, Toni Shiroka
The orthorhombic molybdenum carbide superconductor with $T_c$ = 3.2 K was investigated by muon-spin rotation and relaxation ($mu$SR) measurements and by first-principle calculations. The low-temperature superfluid density, determined by transverse-field $mu$SR, suggests a fully-gapped superconducting state in Mo$_2$C, with a zero-temperature gap $Delta_0$ = 0.44 meV and a magnetic penetration depth $lambda_0$ = 291 nm. The time-reversal symmetry is preserved in the superconducting state, as confirmed by the absence of an additional muon-spin relaxation in the zero-field $mu$SR spectra. Band-structure calculations indicate that the density of states at the Fermi level is dominated by the Mo $4d$-orbitals, which are marginally hybridized with the C $2p$-orbitals over a wide energy range. The symmetry analysis confirms that, in the absence of spin-orbit coupling (SOC), Mo$_2$C hosts twofold-degenerate nodal surfaces and fourfold-degenerate nodal lines. When considering SOC, the fourfold-degenerate nodal lines cross the Fermi level and contribute to the electronic properties. Our results suggest that, similarly to other phases of carbides, also the orthorhombic transition-metal carbides host topological nodal states and may be potential candidates for future studies of topological superconductivity.
通过μ介子自旋旋转和弛豫（$mu$SR）测量以及第一性原理计算，研究了T_c$ = 3.2 K的正交碳化钼超导体。通过横向场$mu$SR测定的低温超流体密度表明，Mo$_2$C中存在一个全隙缝超导态，其零温间隙为$Delta_0$ = 0.44 meV，非磁性穿透深度为$lambda_0$ = 291 nm。带状结构计算表明，费米级的态密度由 Mo 4d 元轨道主导，而 Mo 4d 元轨道在很宽的能量范围内与 C 2p 元轨道有微弱的杂化。对称性分析证实，在没有自旋轨道耦合（SOC）的情况下，Mo$_2$C 存在两重退化的结面和四重退化的结线。当考虑到自旋轨道耦合时，四重退化的结点线穿过费米级并对电子特性做出贡献。我们的研究结果表明，与碳化物的其他相类似，正交过渡金属碳化物也蕴藏着拓扑结点态，可能成为未来拓扑超导研究的潜在候选对象。
{"title":"Nodeless superconductivity and topological nodal states in molybdenum carbide","authors":"Tian Shang, Yuting Wang, Bochen Yu, Keqi Xia, Darek J. Gawryluk, Yang Xu, Qingfeng Zhan, Jianzhou Zhao, Toni Shiroka","doi":"arxiv-2409.02380","DOIUrl":"https://doi.org/arxiv-2409.02380","url":null,"abstract":"The orthorhombic molybdenum carbide superconductor with $T_c$ = 3.2 K was\u0000investigated by muon-spin rotation and relaxation ($mu$SR) measurements and by\u0000first-principle calculations. The low-temperature superfluid density,\u0000determined by transverse-field $mu$SR, suggests a fully-gapped superconducting\u0000state in Mo$_2$C, with a zero-temperature gap $Delta_0$ = 0.44 meV and a\u0000magnetic penetration depth $lambda_0$ = 291 nm. The time-reversal symmetry is\u0000preserved in the superconducting state, as confirmed by the absence of an\u0000additional muon-spin relaxation in the zero-field $mu$SR spectra.\u0000Band-structure calculations indicate that the density of states at the Fermi\u0000level is dominated by the Mo $4d$-orbitals, which are marginally hybridized\u0000with the C $2p$-orbitals over a wide energy range. The symmetry analysis\u0000confirms that, in the absence of spin-orbit coupling (SOC), Mo$_2$C hosts\u0000twofold-degenerate nodal surfaces and fourfold-degenerate nodal lines. When\u0000considering SOC, the fourfold-degenerate nodal lines cross the Fermi level and\u0000contribute to the electronic properties. Our results suggest that, similarly to\u0000other phases of carbides, also the orthorhombic transition-metal carbides host\u0000topological nodal states and may be potential candidates for future studies of\u0000topological superconductivity.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Josephson diode effect (JDE), characterized by asymmetric critical currents in a Josephson junction, has drawn considerable attention in the field of condensed matter physics. We investigate the conditions under which JDE can manifest in a one-dimensional Josephson junction composed of a spin-orbit-coupled quantum wire with an applied Zeeman field, connected between two superconductors. Our study reveals that while spin-orbit coupling (SOC) and a Zeeman field in the quantum wire are not sufficient to induce JDE when the superconductors are purely singlet, the introduction of triplet pairing in the superconductors leads to the emergence of JDE. This finding highlights the potential of JDE as a probe for triplet superconductivity. We further demonstrate that even in absence of SOC in the quantum wire, JDE can arise when the directions of the triplet pairing and the Zeeman field are non-collinear, provided the superconductors exhibit mixed singlet-triplet pairing. Additionally, we identify specific conditions under which JDE is absent, namely, when the pairing is purely triplet and the directions of the SOC and the triplet pairing are perpendicular. Our findings indicate that JDE is always accompanied by the anomalous Josephson effect. The diode effect coefficient is found to oscillate with variations in the chemical potential of the quantum wire, driven by Fabry-P'erot interference effects. Our results suggest that quantum wires in Josephson junctions could serve as effective platforms for probing triplet superconductivity through the observation of JDE.
约瑟夫森二极管效应（JDE）以约瑟夫森结中的不对称临界电流为特征，在凝聚态物理领域引起了广泛关注。我们研究了约瑟夫森二极管效应在一维约瑟夫森结中产生的条件，该结由带有外加泽曼场的自旋轨道耦合量子线组成，连接在两个超导体之间。我们的研究发现，虽然量子线中的自旋轨道耦合（SOC）和泽曼场在超导体为纯单线时不足以诱发 JDE，但在超导体中引入三重配对会导致 JDE 的出现。这一发现凸显了 JDE 作为三重超导探针的潜力。我们进一步证明，即使量子线中不存在SOC，只要超导体表现出单线-三线混合配对，当三线配对和泽曼场的方向不共线时，也会出现JDE。我们的研究结果表明，JDE 总是伴随着反常约瑟夫森效应。在法布里-波特干涉效应的驱动下，二极管效应系数会随着量子线化学势的变化而摆动。我们的研究结果表明，约瑟夫森结中的量子线可以作为通过观察 JDE 来探测三重超导性的有效平台。
{"title":"Josephson diode effect in one-dimensional quantum wires connected to superconductors with mixed singlet-triplet pairing","authors":"Abhiram Soori","doi":"arxiv-2409.02794","DOIUrl":"https://doi.org/arxiv-2409.02794","url":null,"abstract":"The Josephson diode effect (JDE), characterized by asymmetric critical\u0000currents in a Josephson junction, has drawn considerable attention in the field\u0000of condensed matter physics. We investigate the conditions under which JDE can\u0000manifest in a one-dimensional Josephson junction composed of a\u0000spin-orbit-coupled quantum wire with an applied Zeeman field, connected between\u0000two superconductors. Our study reveals that while spin-orbit coupling (SOC) and\u0000a Zeeman field in the quantum wire are not sufficient to induce JDE when the\u0000superconductors are purely singlet, the introduction of triplet pairing in the\u0000superconductors leads to the emergence of JDE. This finding highlights the\u0000potential of JDE as a probe for triplet superconductivity. We further\u0000demonstrate that even in absence of SOC in the quantum wire, JDE can arise when\u0000the directions of the triplet pairing and the Zeeman field are non-collinear,\u0000provided the superconductors exhibit mixed singlet-triplet pairing.\u0000Additionally, we identify specific conditions under which JDE is absent,\u0000namely, when the pairing is purely triplet and the directions of the SOC and\u0000the triplet pairing are perpendicular. Our findings indicate that JDE is always\u0000accompanied by the anomalous Josephson effect. The diode effect coefficient is\u0000found to oscillate with variations in the chemical potential of the quantum\u0000wire, driven by Fabry-P'erot interference effects. Our results suggest that\u0000quantum wires in Josephson junctions could serve as effective platforms for\u0000probing triplet superconductivity through the observation of JDE.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A many body system in the vicinity of a first-order phase transition may get trapped in a local minimum of the free energy landscape. These so-called false-vacuum states may survive for exceedingly long times if the barrier for their decay is high enough. The rich phase diagram obtained in graphene multilayer devices presents a unique opportunity to explore transient superconductivity on top of a correlated false vacuum. Specifically, we consider superconductors which are terminated by an apparent first-order phase transition to a correlated phase with different symmetry. We propose that quenching across this transition leads to a non-equilibrium ephemeral superconductor, readily detectable using straightforward transport measurements. Besides enabling a simple detection scheme, the transient superconductor also generically enhances the false vacuum lifetime, potentially by orders of magnitude. In several scenarios, the complimentary effect takes place as well: superconductivity is temporarily emboldened in the false vacuum, albeit ultimately decaying. We demonstrate the applicability of these claims for two different instances of superconductivity terminated by a first order transition in rhombohedral graphene. The obtained decay timescales position this class of materials as a promising playground to unambiguously realize and measure non-equilibrium superconductivity.
{"title":"Ephemeral Superconductivity Atop the False Vacuum","authors":"Gal Shavit, Stevan Nadj-Perge, Gil Refael","doi":"arxiv-2409.02992","DOIUrl":"https://doi.org/arxiv-2409.02992","url":null,"abstract":"A many body system in the vicinity of a first-order phase transition may get\u0000trapped in a local minimum of the free energy landscape. These so-called\u0000false-vacuum states may survive for exceedingly long times if the barrier for\u0000their decay is high enough. The rich phase diagram obtained in graphene\u0000multilayer devices presents a unique opportunity to explore transient\u0000superconductivity on top of a correlated false vacuum. Specifically, we\u0000consider superconductors which are terminated by an apparent first-order phase\u0000transition to a correlated phase with different symmetry. We propose that\u0000quenching across this transition leads to a non-equilibrium ephemeral\u0000superconductor, readily detectable using straightforward transport\u0000measurements. Besides enabling a simple detection scheme, the transient\u0000superconductor also generically enhances the false vacuum lifetime, potentially\u0000by orders of magnitude. In several scenarios, the complimentary effect takes\u0000place as well: superconductivity is temporarily emboldened in the false vacuum,\u0000albeit ultimately decaying. We demonstrate the applicability of these claims\u0000for two different instances of superconductivity terminated by a first order\u0000transition in rhombohedral graphene. The obtained decay timescales position\u0000this class of materials as a promising playground to unambiguously realize and\u0000measure non-equilibrium superconductivity.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lanthanides ($Ln$) are notoriously difficult to intercalate into graphite. We investigated the possibility of using Na to catalyze the formation of $Ln$-intercalated graphite and successfully synthesized $Ln$C$_6$ ($Ln$ = Sm, Eu, and Yb) significantly rapidly in high yields. The synthesis process involves the formation of the reaction intermediate NaC$_x$, through the mixing of Na and C, which subsequently reacts with $Ln$ upon heating to form $Ln$C$_6$. Well-sintered $Ln$C$_6$ pellets with low residual Na concentrations ($Ln$:Na = 98:2) were fabricated by the two-step method. The pellets enabled the evaluation of $Ln$C$_6$ by powder X-ray diffraction and electrical resistivity measurements. This study highlights the versatility of the Na-catalyzed method and lays the foundation for the rapid mass production of $Ln$C$_6$, with potential applications in superconducting and rechargeable battery materials.
众所周知，镧系元素（$Ln$）很难插层到石墨中。我们研究了使用 Na 催化形成$Ln$插层石墨的可能性，并成功地以高产率快速合成了$Ln$C$$_6$（$Ln$ = Sm、Eu 和 Yb）。合成过程包括通过 Na 和 C 的混合形成反应中间体 NaC$_x$，然后在加热过程中与 $Ln$ 反应形成 $Ln$C$_6$。通过两步法制造出了烧结良好的低残留 Na 浓度（$Ln$:Na = 98:2）$Ln$C$_6$颗粒。通过粉末 X 射线衍射和电电阻率测量，可以对这些颗粒进行 $Ln$C$_6$ 评估。这项研究凸显了 Na 催化方法的多功能性，并为 Ln$C$_6$ 的快速量产奠定了基础，有望应用于超导材料和可充电电池材料。
{"title":"Accelerated Lanthanide Intercalation into Graphite Catalyzed by Na","authors":"Akira Iyo, Hiroshi Fujihisa, Yoshito Gotoh, Shigeyuki Ishida, Hiroshi Eisaki, Hiraku Ogino, Kenji Kawashima","doi":"arxiv-2409.01624","DOIUrl":"https://doi.org/arxiv-2409.01624","url":null,"abstract":"Lanthanides ($Ln$) are notoriously difficult to intercalate into graphite. We\u0000investigated the possibility of using Na to catalyze the formation of\u0000$Ln$-intercalated graphite and successfully synthesized $Ln$C$_6$ ($Ln$ = Sm,\u0000Eu, and Yb) significantly rapidly in high yields. The synthesis process\u0000involves the formation of the reaction intermediate NaC$_x$, through the mixing\u0000of Na and C, which subsequently reacts with $Ln$ upon heating to form\u0000$Ln$C$_6$. Well-sintered $Ln$C$_6$ pellets with low residual Na concentrations\u0000($Ln$:Na = 98:2) were fabricated by the two-step method. The pellets enabled\u0000the evaluation of $Ln$C$_6$ by powder X-ray diffraction and electrical\u0000resistivity measurements. This study highlights the versatility of the\u0000Na-catalyzed method and lays the foundation for the rapid mass production of\u0000$Ln$C$_6$, with potential applications in superconducting and rechargeable\u0000battery materials.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Eric M. Lechner, Olga Trofimova, Jonathan W. Angle, Madison C. DiGuilio, Uttar Pudasaini
While Nb3Sn theoretically offers better superconducting RF cavity performance (Q0 and Eacc) to Nb at any given temperature, peak RF magnetic fields consistently fall short of the 400 mT prediction. The relatively rough topography of vapor-diffused Nb3Sn is widely conjectured to be one of the factors that limit the attainable performance of Nb3Sn-coated Nb cavities prepared via Sn vapor diffusion. Here we investigate the effect of coating duration on the topography of vapor-diffused Nb3Sn on Nb and calculate the associated magnetic field enhancement and superheating field suppression factors using atomic force microscopy topographies. It is shown that the thermally grooved grain boundaries are major defects which may contribute to a substantial decrease in the achievable accelerating field. The severity of these grooves increases with total coating duration due to the deepening of thermal grooves during the coating process.
{"title":"Analysis of Thermal Grooving Effects on Vortex Penetration in Vapor-Diffused Nb3Sn","authors":"Eric M. Lechner, Olga Trofimova, Jonathan W. Angle, Madison C. DiGuilio, Uttar Pudasaini","doi":"arxiv-2409.01569","DOIUrl":"https://doi.org/arxiv-2409.01569","url":null,"abstract":"While Nb3Sn theoretically offers better superconducting RF cavity performance\u0000(Q0 and Eacc) to Nb at any given temperature, peak RF magnetic fields\u0000consistently fall short of the 400 mT prediction. The relatively rough\u0000topography of vapor-diffused Nb3Sn is widely conjectured to be one of the\u0000factors that limit the attainable performance of Nb3Sn-coated Nb cavities\u0000prepared via Sn vapor diffusion. Here we investigate the effect of coating\u0000duration on the topography of vapor-diffused Nb3Sn on Nb and calculate the\u0000associated magnetic field enhancement and superheating field suppression\u0000factors using atomic force microscopy topographies. It is shown that the\u0000thermally grooved grain boundaries are major defects which may contribute to a\u0000substantial decrease in the achievable accelerating field. The severity of\u0000these grooves increases with total coating duration due to the deepening of\u0000thermal grooves during the coating process.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The stable Bardeen-Schrieffer-Cooper (BCS) pairing state of a bosonic system has long been sought theoretically and experimentally. Here we study the BCS state of a binary Bose gas with $s$-wave intra-species repulsions and an inter-species attraction in the mean-field-stable region. We find that above the Bose-Einstein-Condensation (BEC) transtion temperature, there is a phase transtion from the normal state to the BCS state due to inter-species pairing. When the temperature decreases, another phase transtion from the BCS state to the mixture state with both atomic BEC and inter-species pairs occurs. As the temperature is further lowered, the mixuture state is taken over by the BEC state. The phase diagram of this system is presented and experimental implications are discussed.
{"title":"Pairing transitions in a Binary Bose Gas","authors":"Zesheng Shen, Lan Yin","doi":"arxiv-2409.01565","DOIUrl":"https://doi.org/arxiv-2409.01565","url":null,"abstract":"The stable Bardeen-Schrieffer-Cooper (BCS) pairing state of a bosonic system\u0000has long been sought theoretically and experimentally. Here we study the BCS\u0000state of a binary Bose gas with $s$-wave intra-species repulsions and an\u0000inter-species attraction in the mean-field-stable region. We find that above\u0000the Bose-Einstein-Condensation (BEC) transtion temperature, there is a phase\u0000transtion from the normal state to the BCS state due to inter-species pairing.\u0000When the temperature decreases, another phase transtion from the BCS state to\u0000the mixture state with both atomic BEC and inter-species pairs occurs. As the\u0000temperature is further lowered, the mixuture state is taken over by the BEC\u0000state. The phase diagram of this system is presented and experimental\u0000implications are discussed.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Utane NagataDep. Electronic Science and Engineering, Kyoto Univ, Motomi AokiDep. Electronic Science and Engineering, Kyoto UnivCSRN-Kyoto, Akito DaidoGraduate School of Science, Kyoto Univ, Shigeru KasaharaOkayama Univ, Yuichi KasaharaGraduate School of Science, Kyoto Univ, Ryo OhshimaDep. Electronic Science and Engineering, Kyoto UnivCSRN-Kyoto, Yuichiro AndoDep. Electronic Science and Engineering, Kyoto UnivCSRN-Kyoto, Youichi YanaseCSRN-KyotoGraduate School of Science, Kyoto Univ, Yuji MatsudaGraduate School of Science, Kyoto Univ, Masashi ShiraishiDep. Electronic Science and Engineering, Kyoto UnivCSRN-Kyoto
The superconducting diode effect (SDE), where zero-resistance states appear nonreciprocally during current injection, is receiving tremendous interest in both fundamental and applied physics because the SDE is a novel manifestation of symmetry breaking and enables the creation of a novel diode without energy loss. In particular, magnetic-field-free SDEs have been extensively investigated because of their potential to serve as building blocks for superconducting circuit technology. In this letter, we report the field-free SDE in a layered superconductor, FeSe. Its underlying physics is clarified by systematic controlled experiments to be an interplay of a large thermoelectric response and geometrical asymmetry in FeSe. Our findings can pave a new avenue for the construction of novel material and device platforms utilizing SDEs.
{"title":"Field-free superconducting diode effect in layered superconductor FeSe","authors":"Utane NagataDep. Electronic Science and Engineering, Kyoto Univ, Motomi AokiDep. Electronic Science and Engineering, Kyoto UnivCSRN-Kyoto, Akito DaidoGraduate School of Science, Kyoto Univ, Shigeru KasaharaOkayama Univ, Yuichi KasaharaGraduate School of Science, Kyoto Univ, Ryo OhshimaDep. Electronic Science and Engineering, Kyoto UnivCSRN-Kyoto, Yuichiro AndoDep. Electronic Science and Engineering, Kyoto UnivCSRN-Kyoto, Youichi YanaseCSRN-KyotoGraduate School of Science, Kyoto Univ, Yuji MatsudaGraduate School of Science, Kyoto Univ, Masashi ShiraishiDep. Electronic Science and Engineering, Kyoto UnivCSRN-Kyoto","doi":"arxiv-2409.01715","DOIUrl":"https://doi.org/arxiv-2409.01715","url":null,"abstract":"The superconducting diode effect (SDE), where zero-resistance states appear\u0000nonreciprocally during current injection, is receiving tremendous interest in\u0000both fundamental and applied physics because the SDE is a novel manifestation\u0000of symmetry breaking and enables the creation of a novel diode without energy\u0000loss. In particular, magnetic-field-free SDEs have been extensively\u0000investigated because of their potential to serve as building blocks for\u0000superconducting circuit technology. In this letter, we report the field-free\u0000SDE in a layered superconductor, FeSe. Its underlying physics is clarified by\u0000systematic controlled experiments to be an interplay of a large thermoelectric\u0000response and geometrical asymmetry in FeSe. Our findings can pave a new avenue\u0000for the construction of novel material and device platforms utilizing SDEs.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Altermagnetic superconductors hold the potential for novel phenomena, including topological states, finite-momentum superconductivity, as well as promising applications in spintronics. However, an experimental demonstration of the coexistence of these two effects is still lacking. In this work, we propose potential impurities as a way to probe the distinctive properties of altermagnetic superconductors. These impurities induce spin-polarized subgap states that extend along the crystal axes, inheriting the magnetic characteristics of the bulk. When the impurities respect the bulk symmetries, they generate spin-degenerate doublets; otherwise, the degeneracy is lifted. An external magnetic field aligned with the N'eel vector can tune the energies of the spin components of the subgap states. These components show different spatial extensions that can be measured via local probes, like scanning tunneling microscopy. For certain parameters, the impurity state can induce a local sign change on the order parameter, so-called $pi$-transition. Lastly, we investigate the interaction between impurities, revealing a position-dependent effective coupling that facilitates the engineering of spin-dependent tunneling. This tunable coupling introduces a new approach for in-situ control of devices critical for quantum information processing and topological superconductivity.
{"title":"Impurity States in Altermagnetic Superconductors","authors":"Andrea Maiani, Rubén Seoane Souto","doi":"arxiv-2409.01008","DOIUrl":"https://doi.org/arxiv-2409.01008","url":null,"abstract":"Altermagnetic superconductors hold the potential for novel phenomena,\u0000including topological states, finite-momentum superconductivity, as well as\u0000promising applications in spintronics. However, an experimental demonstration\u0000of the coexistence of these two effects is still lacking. In this work, we\u0000propose potential impurities as a way to probe the distinctive properties of\u0000altermagnetic superconductors. These impurities induce spin-polarized subgap\u0000states that extend along the crystal axes, inheriting the magnetic\u0000characteristics of the bulk. When the impurities respect the bulk symmetries,\u0000they generate spin-degenerate doublets; otherwise, the degeneracy is lifted. An\u0000external magnetic field aligned with the N'eel vector can tune the energies of\u0000the spin components of the subgap states. These components show different\u0000spatial extensions that can be measured via local probes, like scanning\u0000tunneling microscopy. For certain parameters, the impurity state can induce a\u0000local sign change on the order parameter, so-called $pi$-transition. Lastly,\u0000we investigate the interaction between impurities, revealing a\u0000position-dependent effective coupling that facilitates the engineering of\u0000spin-dependent tunneling. This tunable coupling introduces a new approach for\u0000in-situ control of devices critical for quantum information processing and\u0000topological superconductivity.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Predicting the change of performance of superconductors under neutron radiation is indispensable for designing compact fusion devices. The favorable enhancement of the critical current caused by flux pinning is separated from the degrading effect of increased scattering of the charge carriers to derive a degradation function from the expected change of the superfluid density (reducing to Homes law in the dirty limit) and the observed increase in flux creep. The degradation turned out to be a universal function of disorder, not depending on the particular tape nor the particle radiation: thermal and/or fast neutrons, as well as 1.2 MeV protons. The universal behavior enables the analysis of changes in flux pinning corrected by the adverse enhancement of scattering. A more reliable prediction of the performance change of coated conductors in a fusion reactor based on proxies for neutrons is anticipated.
{"title":"Universal degradation of high-temperature superconductors due to impurity scattering: predicting the performance loss in fusion magnets","authors":"M. Eisterer, A. Bodenseher, R. Unterrainer","doi":"arxiv-2409.01376","DOIUrl":"https://doi.org/arxiv-2409.01376","url":null,"abstract":"Predicting the change of performance of superconductors under neutron\u0000radiation is indispensable for designing compact fusion devices. The favorable\u0000enhancement of the critical current caused by flux pinning is separated from\u0000the degrading effect of increased scattering of the charge carriers to derive a\u0000degradation function from the expected change of the superfluid density\u0000(reducing to Homes law in the dirty limit) and the observed increase in flux\u0000creep. The degradation turned out to be a universal function of disorder, not\u0000depending on the particular tape nor the particle radiation: thermal and/or\u0000fast neutrons, as well as 1.2 MeV protons. The universal behavior enables the\u0000analysis of changes in flux pinning corrected by the adverse enhancement of\u0000scattering. A more reliable prediction of the performance change of coated\u0000conductors in a fusion reactor based on proxies for neutrons is anticipated.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pair density wave (PDW) is a distinct superconducting state characterized by a periodic modulation of its order parameter in real space. Its intricate interplay with the charge density wave (CDW) state is a continuing topic of interest in condensed matter physics. While PDW states have been discovered in cuprates and other unconventional superconductors, the understanding of diverse PDWs and their interactions with different types of CDWs remains limited. Here, utilizing scanning tunneling microscopy, we unveil the subtle correlations between PDW ground states and two distinct CDW phases -- namely, anion-centered-CDW (AC-CDW) and hollow-centered-CDW (HC-CDW) -- in 2H-NbSe$_2$. In both CDW regions, we observe coexisting PDWs with a commensurate structure that aligns with the underlying CDW phase. The superconducting gap size, $Delta(r)$, related to the pairing order parameter is in phase with the charge density in both CDW regions. Meanwhile, the coherence peak height, $H(r)$, qualitatively reflecting the electron-pair density, exhibits a phase difference of approximately $2pi/3$ relative to the CDW. The three-fold rotational symmetry is preserved in the HC-CDW region but is spontaneously broken in the AC-CDW region due to the PDW state, leading to the emergence of nematic superconductivity.
{"title":"Directly visualizing nematic superconductivity driven by the pair density wave in NbSe$_2$","authors":"Lu Cao, Yucheng Xue, Yingbo Wang, Fu-Chun Zhang, Jian Kang, Hong-Jun Gao, Jinhai Mao, Yuhang Jiang","doi":"arxiv-2409.00660","DOIUrl":"https://doi.org/arxiv-2409.00660","url":null,"abstract":"Pair density wave (PDW) is a distinct superconducting state characterized by\u0000a periodic modulation of its order parameter in real space. Its intricate\u0000interplay with the charge density wave (CDW) state is a continuing topic of\u0000interest in condensed matter physics. While PDW states have been discovered in\u0000cuprates and other unconventional superconductors, the understanding of diverse\u0000PDWs and their interactions with different types of CDWs remains limited. Here,\u0000utilizing scanning tunneling microscopy, we unveil the subtle correlations\u0000between PDW ground states and two distinct CDW phases -- namely,\u0000anion-centered-CDW (AC-CDW) and hollow-centered-CDW (HC-CDW) -- in 2H-NbSe$_2$.\u0000In both CDW regions, we observe coexisting PDWs with a commensurate structure\u0000that aligns with the underlying CDW phase. The superconducting gap size,\u0000$Delta(r)$, related to the pairing order parameter is in phase with the charge\u0000density in both CDW regions. Meanwhile, the coherence peak height, $H(r)$,\u0000qualitatively reflecting the electron-pair density, exhibits a phase difference\u0000of approximately $2pi/3$ relative to the CDW. The three-fold rotational\u0000symmetry is preserved in the HC-CDW region but is spontaneously broken in the\u0000AC-CDW region due to the PDW state, leading to the emergence of nematic\u0000superconductivity.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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