Nature Communications 7, 11570(2016)
Quantum point contacts are cornerstones of mesoscopic physics and central building blocks for quantum electronics. Although the Fermi wavelength in high-quality bulk graphene can be tuned up to hundreds of nanometres, the observation of quantum confinement of Dirac electrons in nanostructured graphene has proven surprisingly challenging. Here we show ballistic transport and quantized conductance of size-confined Dirac fermions in lithographically defined graphene constrictions. At high carrier densities, the observed conductance agrees excellently with the Landauer theory of ballistic transport without any adjustable parameter. Experimental data and simulations for the evolution of the conductance with magnetic field unambiguously confirm the identification of size quantization in the constriction. Close to the charge neutrality point, bias voltage spectroscopy reveals a renormalized Fermi velocity of ~1.5 × 10⁶ ms⁻¹ in our constrictions. Moreover, at low carrier density transport measurements allow probing the density of localized states at edges, thus offering a unique handle on edge physics in graphene devices.

Journal of Magnetism and Magnetic Materials 416,2 (2016)
This “Critical Focused Issue” presents a brief review of experiments and models which describe the origin of exchange bias in epitaxial or textured ferromagnetic/antiferromagnetic bilayers. Evidence is presented which clearly indicates that inner, uncompensated, pinned moments in the bulk of the antiferromagnet (AFM) play a very important role in setting the magnitude of the exchange bias. A critical evaluation of the extensive literature in the field indicates that it is useful to think of this bulk, pinned uncompensated moments as a new type of a ferromagnet which has a low total moment, an ordering temperature given by the AFM Néel temperature, with parallel aligned moments randomly distributed on the regular AFM lattice.

We contributed a book chapter on "Graphene Quantum dots" in "Carbon Nanomaterials Sourcebook: Graphene, Fullerenes, Nanotubes, and Nanodiamonds [Volume I, Klaus D. Sattler(ed.)] by CRC Press ISBN: 9781482252682, April(2016). For more information please see https://www.crcpress.com/Carbon-Nanomaterials-Sourcebook-Graphene-Fullerenes-Nanotubes-and-Nanodiamonds/Sattler/9781482252682.

The Söllerhaus-Workshop 2016 of the 2nd Institute of Physics was a great success.

ACS Appl. Mater. Interfaces 8,9337 (2016)
We present a method to create and erase spatially resolved doping profiles in graphene-hexagonal boron nitride heterostructures. The technique is based on photoinduced doping by a focused laser beam and does neither require masks nor photoresists. This makes our technique interesting for rapid prototyping of unconventional electronic device schemes, where the spatial resolution of the rewritable, long-term stable doping profiles is limited by only the laser spot size (≈600 nm) and the accuracy of sample positioning. Our optical doping method offers a way to implement and to test different, complex doping patterns in one and the very same graphene device, which is not achievable with conventional gating techniques.

Scientific Reports 6, 23547 (2016)
Hexagonal boron nitride (h-BN) is a promising material for implementation in spintronics due to a large band gap, low spin-orbit coupling, and a small lattice mismatch to graphene and to close-packed surfaces of fcc-Ni(111) and hcp-Co(0001). Epitaxial deposition of h-BN on ferromagnetic metals is aimed at small interface scattering of charge and spin carriers. We report on the controlled growth of h-BN/Ni(111) by means of molecular beam epitaxy (MBE). Structural and electronic properties of this system are investigated using cross-section transmission electron microscopy (TEM) and electron spectroscopies which confirm good agreement with the properties of bulk h-BN. The latter are also corroborated by density functional theory (DFT) calculations, revealing that the first h-BN layer at the interface to Ni is metallic. Our investigations demonstrate that MBE is a promising, versatile alternative to both the exfoliation approach and chemical vapour deposition of h-BN.

Luca F. Banszerus, Stephan Engels, and Michael Schmitz from our group have been awarded the "JARA Excellent Junior 2015" for their joint work on „Ultrahigh-mobility graphene devices from chemical vapor deposition on reusable copper“. For more information please see: www.jara.org.