The magnetoresistance of conductors usually has a quadratic dependence on magnetic field 1 , however, examples exist of non-saturating linear behaviour in diverse materials 2-6 . Assigning a specific microscopic mechanism to this unusual phenomenon is obscured by the co-occurrence and interplay of doping, mobility fluctuations and a polycrystalline structure 7,8 . Bilayer graphene has virtually no doping fluctuations, yet provides a built-in mosaic tiling due to the dense network of partial dislocations 9,10 . We present magnetotransport measurements of epitaxial bilayer graphene that exhibits a strong and reproducible linear magnetoresistance that persists to B = 62 T at and above room temperature, decorated by quantum interference effects at low temperatures. Partial dislocations thus have a profound impact on the transport properties in bilayer graphene, a system that is frequently assumed to be dislocation-free. It further provides a clear and tractable model system for studying the unusual properties of mosaic conductors.Although most real materials exhibit a quadratic magnetoresistance (MR), linear MR has been observed, even at room temperature, in conductors as varied as three-dimensional (3D) silver chalcogenides, semiconductors, topological insulators, and 2D multilayer graphenes 2-6,11-14 . Several theories have been developed seeking a general explanation of this phenomenon. A classical mechanism is suspected that mixes the transverse Hall resistance, which is linear in magnetic field, into the longitudinal resistance 1 . In particular, inhomogeneities may allow local Hall currents that in turn modify the potential landscape. The most rigorous model to treat this local Hall current map is that introduced by Parish and Littlewood (PL) in 2003, which represents the material as a mosaic of four-terminal interconnected conductive discs. This model has been invoked to explain linear MR in a number of experimental contexts. Nevertheless, an experiment which links the essence of this insightful but simple model to a real material is still lacking.To make a conceptually clear experiment in the spirit of PL it is first advantageous to treat a 2D system. Not only is magnetotransport an essentially 2D phenomenon, but also the mosaic nature may then in principle be entirely imaged. An essential requirement for a clear experimental realization of the PL model is a material for which the mosaic grains possess negligible internal structure-that is, a constant charge density, mobility and weak magnetoresistance. Furthermore, the granular structure and interconnect topology should be fully characterized. For such an experiment, bilayer epitaxial graphene is an ideal choice as it combines two-dimensionality with fixed charge density (due to the epitaxially defined substrate 15 ) and a room-temperature magnetoresistance expected to be weak 16 . Recently, we have discovered that epitaxial bilayer graphene, despite being a conductor with a good overall mobility, is threaded by a dense network of wellcharacterized partial d...

Single-molecule spintronics investigates electron transport through magnetic molecules that have an internal spin degree of freedom. To understand and control these individual molecules it is important to read their spin state. For unpaired spins, the Kondo effect has been observed as a low-temperature anomaly at small voltages. Here, we show that a coupled spin pair in a single magnetic molecule can be detected and that a bias voltage can be used to switch between two states of the molecule. In particular, we use the mechanically controlled break-junction technique to measure electronic transport through a single-molecule junction containing two coupled spin centres that are confined on two Co(2+) ions. Spin-orbit configuration interaction methods are used to calculate the combined spin system, where the ground state is found to be a pseudo-singlet and the first excitations behave as a pseudo-triplet. Experimentally, these states can be assigned to the absence and occurrence of a Kondo-like zero-bias anomaly in the low-temperature conductance data, respectively. By applying finite bias, we can repeatedly switch between the pseudo-singlet state and the pseudo-triplet state.

Temperature dependence of reversible switch-memory in electron field emission from ultrananocrystalline diamond Appl. Phys. Lett. 101, 173116 (2012) Controlling the current flux in magnetic-barrier induced graphene waveguide Appl. Phys. Lett. 101, 163104 (2012) Resonant tunneling through double barrier graphene systems: A comparative study of Klein and non-Klein tunneling structures J. Appl. Phys. 112, 073711 (2012) Electronic scattering of pseudo-magnetic field induced by local bump in graphene

The observation of non-saturating classical linear magnetoresistivity has been an enigmatic phenomenon in solid state physics. We present a study of a two-dimensional ohmic conductor, including local Hall effect and a self-consistent consideration of the environment. An equivalent-circuit scheme delivers a simple and convincing argument why the magnetoresistivity is linear in strong magnetic field, provided that current and biasing electric field are misaligned by a nonlocal mechanism. A finite-element model of a two-dimensional conductor is suited to display the situations that create such deviating currents. Besides edge effects next to electrodes, charge carrier density fluctuations are efficiently generating this effect. However, mobility fluctuations that have frequently been related to linear magnetoresistivity are barely relevant. Despite its rare observation, linear magnetoresitivity is rather the rule than the exception in a regime of low charge carrier densities, misaligned current pathways and strong magnetic field.

We discuss the difficulties to discover Kondo effect in the resistivity of graphene. Similarly to the Kondo effect, electron-electron interaction effects and weak localization appear as logarithmic corrections to the resistance. In order to disentangle these contributions, a refined analysis of the magnetoconductance and the magnetoresistance is introduced. We present numerical simulations which display the discrimination of both effects. Further, we present experimental data of magnetotransport. When magnetic molecules are added to graphene, a logarithmic correction to the conductance occurs, which apparently suggests Kondo physics. Our thorough evaluation scheme, however, reveals that this interpretation is not conclusive: the data can equally be explained by electron-electron interaction corrections in an inhomogeneous sample. Our evaluation scheme paves the way for a more refined search for the Kondo effect in graphene.The Kondo effect is one of the most intriguing effects in condensed matter physics [1]. It is a consequence of the many-body interaction of magnetic degrees of freedom with the conduction electrons in a metal. We are particularly interested in Kondo effect in graphene, which is expected to be different from Kondo effect in conventional metals due to the specific structure of the quantum mechanical electronic wave function [2]. So far, there is no convincing experimental evidence for Kondo effect in graphene. We consider an earlier apparent finding of Kondo effect as a misinterpretation [3][4][5], the origin of which we elaborate in this manuscript. Graphene, in contrast to conventional (buried) two-dimensional electron gases, provides a unique opportunity to add magnetic degrees of freedom and couple them to the electronic system. They may be added by: (i) structural defects in the graphene layer which are identified as magnetic impurities [6,7], (ii) states with unpaired electrons are present at monolayer/bilayer interfaces, and in dangling-bond states of the substrate [8], (iii) magnetic ions or molecules may be added to the surface of graphene [7,9,10]. This does not mean, however, that Kondo physics is conveniently accessible by experiments: In the low-density electronic system graphene, Kondo temperatures may be extremely small [2] and thus, the effect may be shifted to a temperature regime which is experimentally not accessible. However, with sufficiently strong exchange coupling, and remote from the Dirac point, convenient Kondo temperatures are conceivable.A further experimental difficulty is the unambiguous identification of Kondo effect. The typical trace would be a logarithmic increase of the resistivity ρ(T ) towards low temperatures T , the amplitude of which scales with the density of magnetic impurities. This increase saturates at even lower temperatures when the magnetic impurities are fully screened by the conduction electrons. However, in graphene the two-dimensionality causes the situation that three logarithmic-in-T quantum corrections to the resistivity occur: weak localiz...

We present an overview of recent charge carrier transport experiments in both monolayer and bilayer graphene, with emphasis on the phenomena that appear in large-area samples. While many aspects of transport are based on quantum mechanical concepts, in the large-area limit classical corrections dominate and shape the magnetoresistance and the tunneling conductance. The discussed phenomena are very general and can, with little modification, be expected in any atomically thin 2D conductor.

Using predictive and proactive maintenance methods for critical equipment and processes in industry can help reduce unplanned downtimes and improve process availability and stability. Artificial intelligence (AI) methods for process data analysis can provide plant operators with much-needed insights for decision support and predictive plant maintenance strategies. In this article, a guideline for implementing AI methods in the process industry is provided using the AI-based application Siemens Predictive Analytics (SiePA) and the results of a SiePA application in a milling process are presented.

A simple route to generate magnetotransport data is reported that results in fractional quantum Hall plateaus in the conductance without invoking strongly correlated physics. Ingredients to the generating model are conducting tiles with integer quantum Hall effect and metallic linkers, further Kirchhoff rules. When connecting few identical tiles in a mosaic, fractional steps occur in the conductance values. Richer spectra representing several fractions occur when the tiles are parametrically varied. Parts of the simulation data are supported with purposefully designed graphene mosaics in high magnetic fields. The findings emphasize that the occurrence of fractional conductance values, in particular in two-terminal measurements, does not necessarily indicate interaction-driven physics. The importance of an independent determination of charge densities is underscored and similarities with and differences to the fractional quantum Hall effect are critically discussed.