M. Iavarone

Guiding superconducting vortices with magnetic domain walls.

We demonstrate a unique prospect for inducing anisotropic vortex pinning and manipulating the directional motion of vortices using the stripe domain patterns of a uniaxial magnetic film in a the superconducting/ferromagnetic hybrid. Our observations can be described by a model, which considers interactions between magnetic charges of vortices and surface magnetic charges of domains resulting in the enhanced pinning of vortices on domain walls.

Scanning tunneling spectroscopy in MgB2

Abstract We present extensive scanning tunneling spectroscopy measurements at low temperatures in the multiband superconductor MgB 2 . We find a similar behavior in single crystalline samples and in single grains, which clearly shows the partial superconducting density of states of both the π and σ bands of this material. The superconducting gaps corresponding to both bands are not single valued. Instead, we find a distribution of superconducting gaps centered around 1.9 and 7.5 mV, corresponding respectively to each set of bands. Interband scattering effects, leading to a single gap structure at 4 mV and a smaller critical temperature can be observed in some locations on the surface. S–S junctions formed by pieces of MgB 2 attached to the tip clearly show the subharmonic gap structure associated with this type of junctions. We discuss future developments and possible new effects associated with the multiband nature of superconductivity in this compound.

Superconducting gap anisotropy of LuNi 2 B 2 C thin films from microwave surface impedance measurements

Surface impedance measurements of

Observation of superconducting vortex clusters in S/F hybrids

{mathrm{LuNi}}_{2}{mathrm{B}}_{2}mathrm{C}

Transport and tunneling measurements in superconducting YNi2B2C

superconducting thin films as a function of temperature have been performed down to 1.5 K and at 20 GHz using a dielectric resonator technique. The magnetic penetration depth closely reproduces the standard BCS result, but with a reduced value of the energy gap at low temperature. These data provide evidence for an anisotropic s-wave character of the order parameter symmetry in

Superconducting properties of YNdBaCuO and NdBaCuO thin films deposited by dc sputtering

{mathrm{LuNi}}_{2}{mathrm{B}}_{2}mathrm{C}.

Properties of ErNi2B2C superconducting thin films

From the evaluation of the real part of complex conductivity, we have observed constructive (type II) coherence effects in the electromagnetic absorption below

Microwave properties of RE–Ni2B2C (RE=Y, Er) superconducting thin films

{T}_{c}.

Metastable defects in monolayer and few-layer films of MoS2

While Abrikosov vortices repel each other and form a uniform vortex lattice in bulk type-II superconductors, strong confinement potential profoundly affects their spatial distribution eventually leading to vortex cluster formation. The confinement could be induced by the geometric boundaries in mesoscopic-size superconductors or by the spatial modulation of the magnetic field in superconductor/ferromagnet (S/F) hybrids. Here we study the vortex confinement in S/F thin film heterostructures and we observe that vortex clusters appear near magnetization inhomogeneities in the ferromagnet, called bifurcations. We use magnetic force microscopy to image magnetic bifurcations and superconducting vortices, while high resolution scanning tunneling microscopy is used to obtain detailed information of the local electronic density of states outside and inside the vortex cluster. We find an intervortex spacing at the bifurcation shorter than the one predicted for the same superconductor in a uniform magnetic field equal to the thermodynamical upper critical field Hc2. This result is due to a local enhanced stray field and a competition between vortex-vortex repulsion and Lorentz force. Our findings suggest that special magnetic topologies could result in S/F hybrids that support superconductivity even when locally the vortex density exceeds the thermodynamic critical threshold value beyond which the superconductivity is destroyed.