arXiv subjects

A. Stoehr

Publications and source records attributed to A. Stoehr.

2 recordsLinked to original sources

arXiv2016

Observation of Dirac surface states in the noncentrosymmetric superconductor BiPd

Materials with strong spin-orbit coupling (SOC) have in recent years become a subject of intense research due to their potential applications in spintronics and quantum information technology. In particular, in systems which break inversion symmetry, SOC facilitates the Rashba-Dresselhaus effect, leading to a lifting of spin degeneracy in the bulk and intricate spin textures of the Bloch wave functions. Here, by combining angular resolved photoemission (ARPES) and low temperature scanning tunneling microscopy (STM) measurements with relativistic first-principles band structure calculations, we examine the role of SOC in single crystals of noncentrosymmetric BiPd. We report the detection of several Dirac surface states, one of which exhibits an extremely large spin splitting. Unlike the surface states in inversion-symmetric systems, the Dirac surface states of BiPd have completely different properties at opposite faces of the crystal and are not trivially linked by symmetry. The spin-splitting of the surface states exhibits a strong anisotropy by itself, which can be linked to the low in-plane symmetry of the surface termination.

cond-mat.mtrl-sci↗

arXiv2012

Magnetic field dependence of the critical current in YBa_2Cu_3O_{7-δ}/Au/Nb ramp-zigzag Josephson junctions

We study the critical current I_c dependence on applied magnetic field H for multifacet YBa_2Cu_3O_{7-δ}-Au-Nb ramp-type zigzag Josephson junctions. For many experiments one would like to apply a homogeneous field in the junction plane. However, even tiny misalignments can cause drastic deviations from homogeneity. We show this explicitly by measuring and analyzing I_c vs. H for an 8 facet junction, forming an array of 4\times(0-π)-segments. The ramp angle is θ_r=8^\circ. The facet width is 10\,\mum. H is applied under different angles θrelative to the substrate plane and different angles ϕrelative to the in-plane orientation of the zigzags. We find that a homogeneous flux distribution is only achieved for an angle θ_h\approx 1^\circ - 2^\circ and that even a small misalignment \sim 0.1^\circ relative to θ_h can cause a substantial inhomogeneity of the flux density inside the junction, drastically altering its I_c vs. H interference pattern. We also show, that there is a dead angle θ^*_d relative to θ_h of similar magnitude, where the average flux density completely vanishes.

cond-mat.supr-con↗