title: Current patterns and orbital magnetism in mesoscopic dc transport.
abstract: We present ab initio calculations of the local current density j(r) as it arises in dc-transport measurements. We discover pronounced patterns in the local current density, ring currents ("eddies"), that go along with orbital magnetism. Importantly, the magnitude of the ring currents can exceed the (average) transport current by orders of magnitude. We find associated magnetic fields that exhibit drastic fluctuations with field gradients reaching 1  T nm⁻¹ V⁻¹. The relevance of our observations for spin relaxation in systems with very weak spin-orbit interaction, such as organic semiconductors, is discussed. In such systems, spin relaxation induced by bias driven orbital magnetism competes with relaxation induced by the hyperfine interaction and appears to be of similar strength. We propose a NMR-type experiment in the presence of dc-current flow to observe the spatial fluctuations of the induced magnetic fields.
authors.affiliation: Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76344 Eggenstein-Leopoldshafen, Germany and Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, Campus South, D-76128 Karlsruhe, Germany and Center of Functional Nanostructures, Karlsruhe Institute of Technology, Campus South, D-76131 Karlsruhe, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Walz
authors.affiliation: Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76344 Eggenstein-Leopoldshafen, Germany and Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, Campus South, D-76128 Karlsruhe, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Wilhelm
authors.affiliation: Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76344 Eggenstein-Leopoldshafen, Germany and Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, Campus South, D-76128 Karlsruhe, Germany and Center of Functional Nanostructures, Karlsruhe Institute of Technology, Campus South, D-76131 Karlsruhe, Germany.
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Evers