We theoretically investigate the thermoelectric response of inflated Fermi surfaces (IFSs) generated in a two dimensional unconventional $d$-wave superconductor subjected to an external in-plane Zeeman field. These IFSs exhibiting the same dimension as the underlying normal state Fermi surface are topologically protected by combinations of discrete symmetries. Utilizing the Blonder-Tinkham-Klapwijk formalism and considering normal-$d$-wave superconductor hybrid junction, we compute the thermoelectric coefficients including thermal conductance, Seebeck coefficient, figure of merit ($zT$), and examine the validation of Widemann-Franz law in the presence of both voltage and temperature bias. Importantly, as a signature of anisotropic nature of $d$-wave pairing, Andreev bound states (ABSs) formed at the normal-superconductor interface play a significant role in the thermoelectric response. In the presence of ABSs, we observe a substantial enhancement in Seebeck coefficient ($sim 200,mu$V/K) and $zT$ ($sim 3.5$) due to the generation of the IFSs and thus making such setup a potential candidate for device applications. Finally, we strengthen our continuum model results by computing the thermoelectric coefficients based on a lattice-regularized version of our continuum model.
{"title":"Identifying inflated Fermi surfaces via thermoelectric response in $d$-wave superconductor heterostructure","authors":"Amartya Pal, Paramita Dutta, Arijit Saha","doi":"arxiv-2409.12157","DOIUrl":"https://doi.org/arxiv-2409.12157","url":null,"abstract":"We theoretically investigate the thermoelectric response of inflated Fermi\u0000surfaces (IFSs) generated in a two dimensional unconventional $d$-wave\u0000superconductor subjected to an external in-plane Zeeman field. These IFSs\u0000exhibiting the same dimension as the underlying normal state Fermi surface are\u0000topologically protected by combinations of discrete symmetries. Utilizing the\u0000Blonder-Tinkham-Klapwijk formalism and considering normal-$d$-wave\u0000superconductor hybrid junction, we compute the thermoelectric coefficients\u0000including thermal conductance, Seebeck coefficient, figure of merit ($zT$), and\u0000examine the validation of Widemann-Franz law in the presence of both voltage\u0000and temperature bias. Importantly, as a signature of anisotropic nature of\u0000$d$-wave pairing, Andreev bound states (ABSs) formed at the\u0000normal-superconductor interface play a significant role in the thermoelectric\u0000response. In the presence of ABSs, we observe a substantial enhancement in\u0000Seebeck coefficient ($sim 200,mu$V/K) and $zT$ ($sim 3.5$) due to the\u0000generation of the IFSs and thus making such setup a potential candidate for\u0000device applications. Finally, we strengthen our continuum model results by\u0000computing the thermoelectric coefficients based on a lattice-regularized\u0000version of our continuum model.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253469","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}
We investigate the spatially-resolved dynamics of the collective amplitude Schmid-Higgs (SH) mode in disordered Bardeen-Cooper-Schrieffer (BCS) superconductors and fermionic superfluids. We identify cases where the long-time SH response is determined by a pole in the averaged SH susceptibility, located on the unphysical sheet of its Riemann surface. Using analytic continuation across the two-particle branch cut, we obtain the zero-temperature dispersion relation and damping rate of the SH mode linked to this pole. When the coherence length significantly exceeds the mean free path, the pole is ``hidden'' behind the two-particle continuum edge at $2Delta$, leading to SH oscillations at late times decaying as $1/t^2$ with frequency $2Delta$. Nevertheless, the pole induces a peak in the retarded SH susceptibility at a frequency above $2Delta$ and causes sub-diffusive oscillations with a dynamical exponent $z=4$ at both late times and long distances. Conversely, long-distance oscillations at a fixed frequency $omega$ occur only for $omega$ exceeding $2Delta$, with a spatial period diverging at the threshold as $1/(omega - 2Delta)^{1/4}$, up to logarithmic factors. When the coherence length is comparable to the mean free path, the pole can reemerge into the continuum, resulting in additional late-time oscillations at fixed wave vectors with frequencies above $2Delta$.
{"title":"Spatially-resolved dynamics of the amplitude Schmid-Higgs mode in disordered superconductors","authors":"P. A. Nosov, E. S. Andriyakhina, I. S. Burmistrov","doi":"arxiv-2409.11647","DOIUrl":"https://doi.org/arxiv-2409.11647","url":null,"abstract":"We investigate the spatially-resolved dynamics of the collective amplitude\u0000Schmid-Higgs (SH) mode in disordered Bardeen-Cooper-Schrieffer (BCS)\u0000superconductors and fermionic superfluids. We identify cases where the\u0000long-time SH response is determined by a pole in the averaged SH\u0000susceptibility, located on the unphysical sheet of its Riemann surface. Using\u0000analytic continuation across the two-particle branch cut, we obtain the\u0000zero-temperature dispersion relation and damping rate of the SH mode linked to\u0000this pole. When the coherence length significantly exceeds the mean free path,\u0000the pole is ``hidden'' behind the two-particle continuum edge at $2Delta$,\u0000leading to SH oscillations at late times decaying as $1/t^2$ with frequency\u0000$2Delta$. Nevertheless, the pole induces a peak in the retarded SH\u0000susceptibility at a frequency above $2Delta$ and causes sub-diffusive\u0000oscillations with a dynamical exponent $z=4$ at both late times and long\u0000distances. Conversely, long-distance oscillations at a fixed frequency $omega$\u0000occur only for $omega$ exceeding $2Delta$, with a spatial period diverging at\u0000the threshold as $1/(omega - 2Delta)^{1/4}$, up to logarithmic factors. When\u0000the coherence length is comparable to the mean free path, the pole can reemerge\u0000into the continuum, resulting in additional late-time oscillations at fixed\u0000wave vectors with frequencies above $2Delta$.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253508","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}
We explore the possibility of obtaining new superconductor candidates from functionalized MXene compounds Zr$_2$NS$_2$, Zr$_2$NCl$_2$, and Sc$_2$NCl$_2$ from $textit{ab initio}$ calculations with density functional theory for superconductors (SCDFT). The predicted superconducting transition temperature $T_c$ at ambient pressure may reach up to 11.23 K (Zr$_2$NS$_2$). Strain-induced $T_c$ enhancement is demonstrated with an example case for Zr$_2$NCl$_2$. We note a correlation between the profiles of superconducting gap $Delta$ and the electron-phonon coupling $lambda$ across the Fermi surface for all compounds, which are likely influenced by their modified electronic bandstructure components.
{"title":"Exploring functionalized Zr$_2$N and Sc$_2$N MXenes as superconducting candidates with $textit{ab initio}$ calculations","authors":"Alpin N. Tatan, Osamu Sugino","doi":"arxiv-2409.12052","DOIUrl":"https://doi.org/arxiv-2409.12052","url":null,"abstract":"We explore the possibility of obtaining new superconductor candidates from\u0000functionalized MXene compounds Zr$_2$NS$_2$, Zr$_2$NCl$_2$, and Sc$_2$NCl$_2$\u0000from $textit{ab initio}$ calculations with density functional theory for\u0000superconductors (SCDFT). The predicted superconducting transition temperature\u0000$T_c$ at ambient pressure may reach up to 11.23 K (Zr$_2$NS$_2$).\u0000Strain-induced $T_c$ enhancement is demonstrated with an example case for\u0000Zr$_2$NCl$_2$. We note a correlation between the profiles of superconducting\u0000gap $Delta$ and the electron-phonon coupling $lambda$ across the Fermi\u0000surface for all compounds, which are likely influenced by their modified\u0000electronic bandstructure components.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253470","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}
Thibault Sohier, Marco Gibertini, Ivar Martin, Alberto F. Morpurgo
Superconductivity in few-layer semiconducting transition metal dichalcogenides (TMDs) can be induced by field-effect doping through ionic-liquid gating. While several experimental observations have been collected over the years, a fully-consistent theoretical picture is still missing. Here we develop a realistic framework that combines the predictive power of first-principles simulations with the versatility and insight of Bardeen-Cooper-Schrieffer gap equations to rationalize such experiments. The multi-valley nature of semiconducting TMDs in taken into account, together with the doping- and momentum-dependent electron-phonon and Coulomb interactions. Consistently with experiments, we find that superconductivity occurs when the electron density is large enough that the Q valleys get occupied, as a result of a large enhancement of electron-phonon interactions. Despite being phonon-driven, the superconducting state is predicted to be sensitive to Coulomb interactions, which can lead to the appearance of a relative sign difference between valleys and thus to a $s_{+-}$ character. We discuss qualitatively how such scenario may account for many of the observed physical phenomena for which no microscopic explanation has been found so far, including in particular the presence of a large subgap density of states, and the sample-dependent dome-shaped dependence of $T_c$ on accumulated electron density. Our results provide a comprehensive analysis of gate-induced superconductivity in semiconducting TMDs, and introduce an approach that will likely be valuable for other multivalley electronic systems, in which superconductivity occurs at relatively low electron density.
{"title":"Unconventional gate-induced superconductivity in transition-metal dichalcogenides","authors":"Thibault Sohier, Marco Gibertini, Ivar Martin, Alberto F. Morpurgo","doi":"arxiv-2409.11834","DOIUrl":"https://doi.org/arxiv-2409.11834","url":null,"abstract":"Superconductivity in few-layer semiconducting transition metal\u0000dichalcogenides (TMDs) can be induced by field-effect doping through\u0000ionic-liquid gating. While several experimental observations have been\u0000collected over the years, a fully-consistent theoretical picture is still\u0000missing. Here we develop a realistic framework that combines the predictive\u0000power of first-principles simulations with the versatility and insight of\u0000Bardeen-Cooper-Schrieffer gap equations to rationalize such experiments. The\u0000multi-valley nature of semiconducting TMDs in taken into account, together with\u0000the doping- and momentum-dependent electron-phonon and Coulomb interactions.\u0000Consistently with experiments, we find that superconductivity occurs when the\u0000electron density is large enough that the Q valleys get occupied, as a result\u0000of a large enhancement of electron-phonon interactions. Despite being\u0000phonon-driven, the superconducting state is predicted to be sensitive to\u0000Coulomb interactions, which can lead to the appearance of a relative sign\u0000difference between valleys and thus to a $s_{+-}$ character. We discuss\u0000qualitatively how such scenario may account for many of the observed physical\u0000phenomena for which no microscopic explanation has been found so far, including\u0000in particular the presence of a large subgap density of states, and the\u0000sample-dependent dome-shaped dependence of $T_c$ on accumulated electron\u0000density. Our results provide a comprehensive analysis of gate-induced\u0000superconductivity in semiconducting TMDs, and introduce an approach that will\u0000likely be valuable for other multivalley electronic systems, in which\u0000superconductivity occurs at relatively low electron density.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253503","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}
We theoretically investigate the temperature dependence of nuclear spin-lattice relaxation rate $T_1^{-1}$ in bulk odd-frequency superconductivity. For a model odd-frequency pairing interaction, we first evaluate the superconducting order parameter, within the framework of the combined path-integral formalism with the saddle-point approximation. We then calculate $T_1^{-1}$ below the superconducting phase transition temperature $T_{rm c}$, to see how the odd-frequency pairing affects this physical quantity. In the odd-frequency $p$-wave state, while the so-called coherence peak is suppressed as in the even-frequency $p$-wave case, $T_1^{-1}$ is found to exhibit the Korringa-law-like behavior ($T_1^{-1}propto T$) except just below $T_{rm c}$, even without impurity scatterings. In the odd-frequency $s$-wave case, the behavior of $T_{1}^{-1}$ is found to be sensitive to the detailed spin structure of the superconducting order parameter: In a case, $T_1^{-1}$ is enhanced far below $T_{rm c}$, being in contrast to the conventional (even-frequency) $s$-wave BCS case, where the coherence peak appears just below $T_{rm c}$. We also show that the calculated $T_1^{-1}$ in the odd-frequency $p$-wave case well explains the recent experiment on CeRh$_{0.5}$Ir$_{0.5}$In$_5$, where the possibility of odd-frequency $p$-wave superconductivity was recently suggested experimentally.
{"title":"Nuclear Spin-Lattice Relaxation Rate in Odd-Frequency Superconductivity","authors":"Shumpei Iwasaki, Yoji Ohashi","doi":"arxiv-2409.10894","DOIUrl":"https://doi.org/arxiv-2409.10894","url":null,"abstract":"We theoretically investigate the temperature dependence of nuclear\u0000spin-lattice relaxation rate $T_1^{-1}$ in bulk odd-frequency\u0000superconductivity. For a model odd-frequency pairing interaction, we first\u0000evaluate the superconducting order parameter, within the framework of the\u0000combined path-integral formalism with the saddle-point approximation. We then\u0000calculate $T_1^{-1}$ below the superconducting phase transition temperature\u0000$T_{rm c}$, to see how the odd-frequency pairing affects this physical\u0000quantity. In the odd-frequency $p$-wave state, while the so-called coherence\u0000peak is suppressed as in the even-frequency $p$-wave case, $T_1^{-1}$ is found\u0000to exhibit the Korringa-law-like behavior ($T_1^{-1}propto T$) except just\u0000below $T_{rm c}$, even without impurity scatterings. In the odd-frequency\u0000$s$-wave case, the behavior of $T_{1}^{-1}$ is found to be sensitive to the\u0000detailed spin structure of the superconducting order parameter: In a case,\u0000$T_1^{-1}$ is enhanced far below $T_{rm c}$, being in contrast to the\u0000conventional (even-frequency) $s$-wave BCS case, where the coherence peak\u0000appears just below $T_{rm c}$. We also show that the calculated $T_1^{-1}$ in\u0000the odd-frequency $p$-wave case well explains the recent experiment on\u0000CeRh$_{0.5}$Ir$_{0.5}$In$_5$, where the possibility of odd-frequency $p$-wave\u0000superconductivity was recently suggested experimentally.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253506","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}
Flat-band systems are of great interest due to their strong electron correlations and unique band geometry. Recent studies have linked the properties of Cooper pairs in flat-band superconductors to the quantum metric. Unlike prior studies primarily focused on quasiparticle fluctuations, in this work, we investigate quantum geometric effects on a collective mode of the order parameter-the Higgs mode. We derive the quantum goemetric Higgs-mode correlation length and investigate whether the nonlinear electromagnetic response of the Higgs mode persists in flat band. It turns out that the quantum metric will replaces energy derivatives, playing a crucial role in third-harmonic generation(THG). We further numerically calculated the correlation length and THG in the Lieb lattice. In contrast to traditional single-band results, Higgs mode fluctuations contribute almost entirely to THG, with the quasiparticle contribution being negligible. This finding provides valuable guidance for detecting Higgs modes in flat-band systems through optical methods and reveals the profound influence of quantum geometry in flat-band systems.
{"title":"Quantum Geometric Effects on the Higgs Mode in Flat-band Superconductors","authors":"Yuhang Xiao, Ning Hao","doi":"arxiv-2409.10891","DOIUrl":"https://doi.org/arxiv-2409.10891","url":null,"abstract":"Flat-band systems are of great interest due to their strong electron\u0000correlations and unique band geometry. Recent studies have linked the\u0000properties of Cooper pairs in flat-band superconductors to the quantum metric.\u0000Unlike prior studies primarily focused on quasiparticle fluctuations, in this\u0000work, we investigate quantum geometric effects on a collective mode of the\u0000order parameter-the Higgs mode. We derive the quantum goemetric Higgs-mode\u0000correlation length and investigate whether the nonlinear electromagnetic\u0000response of the Higgs mode persists in flat band. It turns out that the quantum\u0000metric will replaces energy derivatives, playing a crucial role in\u0000third-harmonic generation(THG). We further numerically calculated the\u0000correlation length and THG in the Lieb lattice. In contrast to traditional\u0000single-band results, Higgs mode fluctuations contribute almost entirely to THG,\u0000with the quasiparticle contribution being negligible. This finding provides\u0000valuable guidance for detecting Higgs modes in flat-band systems through\u0000optical methods and reveals the profound influence of quantum geometry in\u0000flat-band systems.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253505","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}
Manasi Mandal, A. Kataria, P. K. Meena, R. K. Kushwaha, D. Singh, P. K. Biswas, R. Stewart, A. D. Hillier, R. P. Singh
We investigated the Re-based kagome superconductor Re$_2$Zr through various measurements, including resistivity, magnetization, specific heat, and muon spin rotation and relaxation spectroscopy. These results suggest that Re$_2$Zr is a moderately coupled potential two-gap superconductor. Zero-field muon relaxation data indicate the possible presence of a time-reversal symmetry-breaking state in the superconducting ground state. Our investigation identifies Re$_{2}$Zr as a new unconventional superconductor with a potential complex order parameter that warrants considerable experimental and theoretical interest.
{"title":"Time-Reversal Symmetry Breaking in Re-Based Kagome Lattice Superconductor","authors":"Manasi Mandal, A. Kataria, P. K. Meena, R. K. Kushwaha, D. Singh, P. K. Biswas, R. Stewart, A. D. Hillier, R. P. Singh","doi":"arxiv-2409.10941","DOIUrl":"https://doi.org/arxiv-2409.10941","url":null,"abstract":"We investigated the Re-based kagome superconductor Re$_2$Zr through various\u0000measurements, including resistivity, magnetization, specific heat, and muon\u0000spin rotation and relaxation spectroscopy. These results suggest that Re$_2$Zr\u0000is a moderately coupled potential two-gap superconductor. Zero-field muon\u0000relaxation data indicate the possible presence of a time-reversal\u0000symmetry-breaking state in the superconducting ground state. Our investigation\u0000identifies Re$_{2}$Zr as a new unconventional superconductor with a potential\u0000complex order parameter that warrants considerable experimental and theoretical\u0000interest.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253504","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}
Aswin kumar Anbalagan, Rebecca Cummings, Chenyu Zhou, Junsik Mun, Vesna Stanic, Jean Jordan-Sweet, Juntao Yao, Kim Kisslinger, Conan Weiland, Dmytro Nykypanchuk, Steven L. Hulbert, Qiang Li, Yimei Zhu, Mingzhao Liu, Peter V. Sushko, Andrew L. Walter, Andi M. Barbour
Despite constituting a smaller fraction of the qubits electromagnetic mode, surfaces and interfaces can exert significant influence as sources of high-loss tangents, which brings forward the need to reveal properties of these extended defects and identify routes to their control. Here, we examine the structure and composition of the metal-substrate interfacial layer that exists in Ta/sapphire-based superconducting films. Synchrotron-based X-ray reflectivity measurements of Ta films, commonly used in these qubits, reveal an unexplored interface layer at the metal-substrate interface. Scanning transmission electron microscopy and core-level electron energy loss spectroscopy identified an approximately 0.65 text{nm} pm 0.05 text{nm} thick intermixing layer at the metal-substrate interface containing Al, O, and Ta atoms. Density functional theory (DFT) modeling reveals that the structure and properties of the Ta/sapphire heterojunctions are determined by the oxygen content on the sapphire surface prior to Ta deposition, as discussed for the limiting cases of Ta films on the O-rich versus Al-rich Al2O3 (0001) surface. By using a multimodal approach, integrating various material characterization techniques and DFT modeling, we have gained deeper insights into the interface layer between the metal and substrate. This intermixing at the metal-substrate interface influences their thermodynamic stability and electronic behavior, which may affect qubit performance.
尽管表面和界面在量子比特电磁模式中所占的比例较小，但它们作为高孤度量子的来源却能产生重大影响，这就提出了揭示这些扩展缺陷的特性并确定其控制途径的必要性。在这里，我们研究了存在于基于钽/蓝宝石的超导薄膜中的金属-基底界面层的结构和组成。对这些量子比特中常用的钽薄膜进行的同步加速器 X 射线反射率测量显示，在金属-基底界面上存在一个尚未探索的界面层。扫描透射电子显微镜和核级电子能量损失光谱发现了一个大约 0.65 text{nm｝ppm 0.05 text{nm} 厚的互混层，该层位于金属-基底界面，包含 Al、O 和 Ta 原子。密度函数理论（DFT）建模表明，Ta/蓝宝石异质结的结构和特性取决于Ta沉积前蓝宝石表面的氧含量，这一点已在富O和富Al的Al2O3 (0001)表面Ta薄膜的极限情况中讨论过。通过采用多模式方法，整合各种材料表征技术和 DFT 建模，我们对金属与基底之间的界面层有了更深入的了解。金属与衬底界面层的混杂会影响它们的热力学稳定性和电子行为，从而可能影响量子比特的性能。
{"title":"Revealing the Origin and Nature of the Buried Metal-Substrate Interface Layer in Ta/Sapphire Superconducting Films","authors":"Aswin kumar Anbalagan, Rebecca Cummings, Chenyu Zhou, Junsik Mun, Vesna Stanic, Jean Jordan-Sweet, Juntao Yao, Kim Kisslinger, Conan Weiland, Dmytro Nykypanchuk, Steven L. Hulbert, Qiang Li, Yimei Zhu, Mingzhao Liu, Peter V. Sushko, Andrew L. Walter, Andi M. Barbour","doi":"arxiv-2409.10780","DOIUrl":"https://doi.org/arxiv-2409.10780","url":null,"abstract":"Despite constituting a smaller fraction of the qubits electromagnetic mode,\u0000surfaces and interfaces can exert significant influence as sources of high-loss\u0000tangents, which brings forward the need to reveal properties of these extended\u0000defects and identify routes to their control. Here, we examine the structure\u0000and composition of the metal-substrate interfacial layer that exists in\u0000Ta/sapphire-based superconducting films. Synchrotron-based X-ray reflectivity\u0000measurements of Ta films, commonly used in these qubits, reveal an unexplored\u0000interface layer at the metal-substrate interface. Scanning transmission\u0000electron microscopy and core-level electron energy loss spectroscopy identified\u0000an approximately 0.65 text{nm} pm 0.05 text{nm} thick intermixing layer\u0000at the metal-substrate interface containing Al, O, and Ta atoms. Density\u0000functional theory (DFT) modeling reveals that the structure and properties of\u0000the Ta/sapphire heterojunctions are determined by the oxygen content on the\u0000sapphire surface prior to Ta deposition, as discussed for the limiting cases of\u0000Ta films on the O-rich versus Al-rich Al2O3 (0001) surface. By using a\u0000multimodal approach, integrating various material characterization techniques\u0000and DFT modeling, we have gained deeper insights into the interface layer\u0000between the metal and substrate. This intermixing at the metal-substrate\u0000interface influences their thermodynamic stability and electronic behavior,\u0000which may affect qubit performance.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253507","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}
We study the diode effect of the supercurrent in the Josephson junctions with the loop current states as the tunneling barrier. The loop current states are realized by the Haldane model which preserves the inversion symmetry and thus forbids the diode effect. We demonstrate how the inversion symmetry can be broken in the monolayer and bilayer systems. In the monolayer system, inversion symmetry can be broken by either introducing a sublattice staggered potential for the Haldane model or introducing a modified Haldane model, and in the bilayer system, it can be broken by either staking the two layers with opposite current directions or by directly applying an electric field perpendicular to the layers. We further show that the diode efficiency can be tuned by the interlayer coupling and the strength of the electric field or interlayer voltage. Our results provide another route to realize the Josephson diode effect by breaking the time-reversal symmetry through the loop-current states.
{"title":"Josephson diodes induced by the loop current states","authors":"Qi-Kai Shen, Yi Zhang","doi":"arxiv-2409.09938","DOIUrl":"https://doi.org/arxiv-2409.09938","url":null,"abstract":"We study the diode effect of the supercurrent in the Josephson junctions with\u0000the loop current states as the tunneling barrier. The loop current states are\u0000realized by the Haldane model which preserves the inversion symmetry and thus\u0000forbids the diode effect. We demonstrate how the inversion symmetry can be\u0000broken in the monolayer and bilayer systems. In the monolayer system, inversion\u0000symmetry can be broken by either introducing a sublattice staggered potential\u0000for the Haldane model or introducing a modified Haldane model, and in the\u0000bilayer system, it can be broken by either staking the two layers with opposite\u0000current directions or by directly applying an electric field perpendicular to\u0000the layers. We further show that the diode efficiency can be tuned by the\u0000interlayer coupling and the strength of the electric field or interlayer\u0000voltage. Our results provide another route to realize the Josephson diode\u0000effect by breaking the time-reversal symmetry through the loop-current states.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268811","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}
We study the magnon spectrum in a thin ferromagnetic-superconductor heterostructure in the presence of a single superconducting vortex. We employ the Bogolubov-de Gennes Hamiltonian which describes the magnons in the presence of the stray magnetic field and the non-uniform magnetic texture induced by the vortex. We find that the vortex localizes magnon states approximately in the same way as a charge center produces electron bound states due to screened Coulomb interaction in the two-dimensional electron gas. The number of these localized states is substantially determined by the material parameters of the ferromagnetic film only. We solve the scattering problem for an incident plane spin wave and compute the total and transport cross sections. We demonstrate that the vortex-induced non-uniform magnetic texture in chiral ferromagnetic film produces a skew scattering of magnons. We explore the peculiarities of the quantum scattering problem that correspond to orbiting in the classical limit.
{"title":"Bound states and scattering of magnons on a superconducting vortex in ferromagnet-superconductor heterostructures","authors":"D. S. Katkov, S. S. Apostoloff, I. S. Burmistrov","doi":"arxiv-2409.10220","DOIUrl":"https://doi.org/arxiv-2409.10220","url":null,"abstract":"We study the magnon spectrum in a thin ferromagnetic-superconductor\u0000heterostructure in the presence of a single superconducting vortex. We employ\u0000the Bogolubov-de Gennes Hamiltonian which describes the magnons in the presence\u0000of the stray magnetic field and the non-uniform magnetic texture induced by the\u0000vortex. We find that the vortex localizes magnon states approximately in the\u0000same way as a charge center produces electron bound states due to screened\u0000Coulomb interaction in the two-dimensional electron gas. The number of these\u0000localized states is substantially determined by the material parameters of the\u0000ferromagnetic film only. We solve the scattering problem for an incident plane\u0000spin wave and compute the total and transport cross sections. We demonstrate\u0000that the vortex-induced non-uniform magnetic texture in chiral ferromagnetic\u0000film produces a skew scattering of magnons. We explore the peculiarities of the\u0000quantum scattering problem that correspond to orbiting in the classical limit.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253514","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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