In multiband superconductors, each superconducting condensate supports vortices with fractional quantum flux. In the ground state, vortices in different bands are spatially bounded together to form a composite vortex, carrying one quantum flux Φ_0. Here we predict dissociation of the composite vortices lattice in the flux flow state due to the disparity of the vortex viscosity and flux of the vortex in different bands. For a small driving current, composite vortices start to deform, but the constituting vortices in different bands move with the same velocity. For a large current, composite vortices dissociate and vortices in different bands move with different velocities. The dissociation transition shows up as an increase of flux flow resistivity. In the dissociated phase, Shapiro steps are developed when an ac current is superimposed with a dc current.
We use large-scale Monte-Carlo simulations to study thermal fluctuations in chiral $p$-wave superconductors in an applied magnetic field in three dimensions. We consider the thermal stability of previously predicted unusual double-quanta flux-line lattice ground states in such superconductors. In previous works it was shown that, neglecting thermal fluctuations, a chiral $p$-wave superconductor forms an hexagonal lattice of doubly-quantized vortices, except extremely close to the vicinity of $H_{c2}$ where double-quanta vortices split apart. We find dissociation of double-quanta vortices drive…
We consider $\mathrm{SU}(N)$-symmetric Ginzburg-Landau models coupled to non-compact Abelian gauge field focusing on the case $N > 2$ at finite temperature. We show that, at least for sufficiently large gauge-field coupling constants, these models have two phase transitions. The intermediate phase between the symmetric and low-temperature phases is a state with composite neutral order and no Meissner effect. In this neutral phase the system spontaneously breaks only the symmetry associated with phase differences and density differences between components. For $N > 2$, in contrast to the $SU(2)…
Magnetic-field tuned superconductor to insulator transition was observed in a novel hybrid system of granular superconducting indium, deposited on indium oxide thin film, which exhibits global superconductivity at low magnetic fields. We have used annealing to tune the coupling to lie just at the borderline where superconductivity in the underlying InOx is suppressed, which is also close to the metal-insulator transition of the InOx. The hybrid system exhibits a "giant" magnetoresistance above the H-SIT, with critical behavior that manifests the duality between Cooper pairs and vortices.
在非常各向异性的层状超导体（例如Bi $_2$ Sr $_2$ CaCu $_2$ O $_x$）中，倾斜的磁场可以作为平行和垂直于层的两个共存的涡旋晶格而穿透。在低出平面场的垂直涡形成一组孤立的涡链，最近已经详细观察到扫描霍尔探针测量。我们目前的计算表明，这种孤立链状态的一个非常微妙的稳定性。随着涡旋密度沿链的增加，存在向屈曲链的一级转变，然后链将在向复合链状态的连续转变中排出涡旋。在低密度下，由于链上的涡旋之间的长程吸引力，存在朝向聚集的不稳定性，并且在非常低的密度下，它变得在能量上有利于形成倾斜的链，这可以解释在最近的实验中看到的沿着链的涡旋的突然消失。
We investigate theoretically the equilibrium configurations of many magnetic skyrmions interacting with many superconducting vortices in a superconductor-chiral magnet bilayer. We show that miscible mixtures of vortices and skyrmions in this system breaks down at a particular wave number for sufficiently strong coupling, giving place to remarkably diverse mesoscale patterns: gel, stripes, clusters, intercalated stripes and composite gel-cluster structures. We also demonstrate that, by appropriate choice of parameters, one can thermally tune between the homogeneous and density-modulated phases.
Multiband superconductors have a sufficient number of degrees of freedom to allow topological excitations characterized by Skyrmionic topological invariants. In the most common, clean s-wave multiband, systems the interband magnetic coupling favours composite vortex solutions, without a Skyrmionic topological charge. It was discussed recently that certain kinds of anisotropies lead to hybridisation of the interband phase difference (Leggett) mode with magnetic modes, dramatically changing the hydromagnetostatics of the system. Here we report this effect for a range of parameters that substanti…
The composite cosmological objects -- Kibble-Lazarides-Shafi (KLS) walls bounded by strings and cosmic strings terminated by Nambu monopoles -- could be produced during the phase transitions in the early Universe. Recent experiments in superfluid $^3$He reproduced the formation of the KLS domain walls, which opened the new arena for the detailed study of those objects in human controlled system with different characteristic lengths. These composite defects are formed by two successive symmetry breaking phase transitions. In the first transition the strings are formed, then in the second transi…
We provide a microscopic-level derivation of earlier results showing that, in the critical vicinity of the superconductor-to-insulator transition (SIT), disorder and localization become negligible and the structure of the emergent phases is determined by topological effects arising from the competition between two quantum orders, superconductivity and superinsulation. We find that, around the critical point, the ground state is a composite incompressible quantum fluid of Cooper pairs and vortices coexisting with an intertwined Wigner crystal for the excess (with respect to integer filling) exc…
Angularly Selective Enhanced Vortex Screening in Extremely Layered Superconductors with Tilted Columnar Defects
Low Temperatures Lab, Centro Atómico Bariloche, CNEA（低温实验室，巴里洛切原子中心，国家原子能委员会）；Instituto de Nanociencia y Nanotecnología, CONICET-CNEA, Nodo Bariloche（纳米科学与技术研究所，CONICET-CNEA，巴里洛切节点）；Instituto Balseiro, CNEA and Universidad Nacional de Cuyo（巴尔塞罗研究所，国家原子能委员会和库约国立大学）；Neutrons Beam National Lab, CNEA（中子束国家实验室，国家原子能委员会）；Vmnetic SAS；Laboratoire des Solides Irradiés, CEA/DRF/IRAMIS, École Polytechnique, CNRS, Institut Polytechnique de Paris（辐照固体实验室，CEA/DRF/IRAMIS，巴黎综合理工学院，CNRS，巴黎理工学院）
