In this paper, we consider a quantum dot connected to four superconducting terminals biased at opposite voltages on the quartet line. The grounded superconductor contains a loop threaded by the magnetic flux $Φ$. We provide Keldysh microscopic calculations and physical pictures for the voltage-$V$ dependence of the quartet current. Superconductivity is expected to be stronger at $Φ/Φ_0=0$ than at $Φ/Φ_0=1/2$. However, inversion $I_{q,c}(V,0)<I_{q,c}(V,1/2)$ is obtained in the critical current $I_{q,c}(V,Φ/Φ_0)$ on the quartet line in the voltage-$V$ ranges which match avoided crossings in the Floquet spectrum at $(V,Φ/Φ_0=0)$ but not at $(V,1/2)$. A reduction in $I_{q,c}$ appears in the vicinity of those avoided crossings, where Landau-Zener tunneling produces dynamical quantum mechanical superpositions of the Andreev bound states. In addition, $π$-$0$ and $0$-$π$ cross-overs emerge in the current-phase relations as $V$ is further increased. The voltage-induced $π$-shift is interpreted as originating from the nonequilibrium Floquet populations produced by voltage biasing. The numerical calculations reveal that the inversion is robust against strong Landau-Zener tunneling and many levels in the quantum dot. Our theory provides a simple ``Floquet level and population'' mechanism for inversion tuned by the bias voltage $V$, which paves the way towards more realistic models for the recent Harvard group experiment where the inversion is observed.
Hybridization of topologically distinct quartet modes in three-terminal graphene Josephson junctions
The Pennsylvania State University（宾夕法尼亚州立大学）；National Institute for Materials Science（国立材料研究所）；Université Grenoble-Alpes（格勒诺布尔阿尔卑斯大学）；CNRS（法国国家科学研究中心）；Grenoble INP（格勒诺布尔理工学院）；Institut NEEL（NEEL研究所）
Revisiting the adiabatic limit in ballistic multiterminal Josephson junctions
Université Grenoble-Alpes, CNRS, Grenoble INP, Institut NEEL（格勒诺布尔阿尔卑斯大学、法国国家科学研究中心、格勒诺布尔理工学院、NEEL研究所）；The Pennsylvania State University（宾夕法尼亚州立大学）；Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院）
Université Grenoble-Alpes, CNRS, Grenoble INP, Institut NEEL（格勒诺布尔阿尔卑斯大学、法国国家科学研究中心、格勒诺布尔理工学院、NEEL研究所）；Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院量子材料与技术研究所）；Department of Electrical Engineering, The Pennsylvania State University（宾夕法尼亚州立大学电气工程系）
Spin-charge conversion in multiterminal Aharonov-Casher ring coupled to precessing ferromagnets: A charge conserving Floquet-nonequilibrium Green function approach
我们导出了描述开放量子系统的Floquet非平衡格林函数（Floquet-NEGF）的非微扰解.通过采用减少区域计划，我们得到的表达式呈现保守的电荷电流为任何给定的最大数量的光子，区别于其他现有的Floquet-NEGF为基础的表达式，不太可行，无限数量的光子需要考虑到，以确保守恒。为了证明我们导出的形式主义和研究自旋-电荷转换的自旋轨道耦合（SOC），我们认为自旋驱动的设置作为互易的电驱动设置在S。Souma et.例如，B 70，195346（2004）和Phys. Rev. Lett. 94，106602（2005）。在我们的设置中，纯自旋电流由旋进铁磁（FM）岛的磁化动力学驱动，然后被泵入Rashba SOC的相邻两端或四端介观Aharonov-Casher（AC）环，在那里发生自旋-电荷转换。我们的自旋驱动的结果显示出互惠的功能，非常同意在上述电驱动的设置中的发现。我们提出了两种对称操作，下的交流环哈密顿量是不变的，论证了泵/转换电流的关系，在同一个或不同的泵配置的引线。对称性参数与环宽度和引线、端子和旋进FM岛中的开放通道的数量无关。特别地，对于两个端子和两个旋进FM岛的某些设置，可以在引线中产生净纯平面内自旋电流和纯自旋电流，其中电流幅度和偏振方向可通过泵浦配置来调节。覆盖FM岛之间的双端AC环的栅极电压。
Robustness of quantized transport through edge states of finite length: Imaging current density in Floquet topological vs. quantum spin and anomalous Hall insulators
Topological signatures in the quench dynamics of periodically driven quantum systems
Indian Institute of Science Education and Research Tirupati（印度科学教育与研究学院蒂鲁帕提分校）；Indian Institute of Technology Kanpur（坎普尔印度理工学院）；Indian Institute of Science, Bengaluru（班加罗尔印度科学学院）
