Syntaktische Konstanten und lexikalische Besonderheiten in der deutschen Sprache der Gegenwart

植松健郎教授古稀・退職記念

Old and new progressive forms in German

In recent times, German as a language with a well-functioning tense system is developing a special progressive form, marking actions and processes which are continual and not yet terminated. There is a variety of forms like beim Arbeiten or gerade im Begriff sein zu arbeiten, but most usual and by far most grammaticalised is the am-progressive (er ist am Arbeiten, “he is working”). In this paper the restrictions which still exist are discussed. They are limited, but although they are not entirely accepted in standard German, the range of these constructions is extensive. In spite of this fact, the German language does not tend to develop general aspectual markers. A comparison with English shows this clearly. However, in its early periods the German language had overt aspectual characteristics. Especially constructions with the present participle and the auxiliary verbs sein and warden could function as aspect partners. These constructions gradually disappeared at the end of Middle High German. Thus, modern German has only very few aspectual markers, which are restricted to progressive constructions verbalizing actions and processes in actual situations.In recent times, German as a language with a well-functioning tense system is developing a special progressive form, marking actions and processes which are continual and not yet terminated. There is a variety of forms like beim Arbeiten or gerade im Begriff sein zu arbeiten, but most usual and by far most grammaticalised is the am-progressive (er ist am Arbeiten, “he is working”). In this paper the restrictions which still exist are discussed. They are limited, but although they are not entirely accepted in standard German, the range of these constructions is extensive. In spite of this fact, the German language does not tend to develop general aspectual markers. A comparison with English shows this clearly. However, in its early periods the German language had overt aspectual characteristics. Especially constructions with the present participle and the auxiliary verbs sein and warden could function as aspect partners. These constructions gradually disappeared at the end of Middle High German. Thus, modern German has only very few aspectual markers, which are restricted to progressive constructions verbalizing actions and processes in actual situations.In recent times, German as a language with a well-functioning tense system is developing a special progressive form, marking actions and processes which are continual and not yet terminated. There is a variety of forms like beim Arbeiten or gerade im Begriff sein zu arbeiten, but most usual and by far most grammaticalised is the am-progressive (er ist am Arbeiten, “he is working”). In this paper the restrictions which still exist are discussed. They are limited, but although they are not entirely accepted in standard German, the range of these constructions is extensive. In spite of this fact, the German language does not tend to develop general aspectual markers. A comparison with English shows this clearly. However, in its early periods the German language had overt aspectual characteristics. Especially constructions with the present participle and the auxiliary verbs sein and warden could function as aspect partners. These constructions gradually disappeared at the end of Middle High German. Thus, modern German has only very few aspectual markers, which are restricted to progressive constructions verbalizing actions and processes in actual situations

Weak Localization and Transport Gap in Graphene Antidot Lattices

We fabricated and measured antidot lattices in single layer graphene with lattice periods down to 90 nm. In large-period lattices, a well-defined quantum Hall effect is observed. Going to smaller antidot spacings the quantum Hall effect gradually disappears, following a geometric size effect. Lattices with narrow constrictions between the antidots behave as networks of nanoribbons, showing a high-resistance state and a transport gap of a few mV around the Dirac point. We observe pronounced weak localization in the magnetoresistance, indicating strong intervalley scattering at the antidot edges. The area of phase-coherent paths is bounded by the unit cell size at low temperatures, so each unit cell of the lattice acts as a ballistic cavity.Comment: some revisions, to appear in New Journal of Physics, Special Issue Graphen

Scanning Raman spectroscopy of graphene antidot lattices: Evidence for systematic p-type doping

We have investigated antidot lattices, which were prepared on exfoliated graphene single layers via electron-beam lithography and ion etching, by means of scanning Raman spectroscopy. The peak positions, peak widths and intensities of the characteristic phonon modes of the carbon lattice have been studied systematically in a series of samples. In the patterned samples, we found a systematic stiffening of the G band mode, accompanied by a line narrowing, while the 2D mode energies are found to be linearly correlated with the G mode energies. We interpret this as evidence for p-type doping of the nanostructured graphene

Morphology and flexibility of graphene and few-layer graphene on various substrates

We report on detailed microscopy studies of graphene and few-layer-graphene produced by mechanical exfoliation on various semi-conducting substrates. We demonstrate the possibility to prepare and analyze graphene on (001)-GaAs, manganese p-doped (001)-GaAs and InGaAs substrates. The morphology of graphene on these substrates was investigated by scanning electron and atomic force microscopy and compared to layers on silicon oxide. It was found that graphene sheets strongly follow the texture of the sustaining substrates independent on doping, polarity or roughness. Furthermore resist residues exist on top of graphene after a lithographic step. The obtained results provide the opportunity to research the graphene-substrate interactions

Dynamical Coulomb blockade and spin-entangled electrons

We consider the production of mobile and nonlocal pairwise spin-entangled electrons from tunneling of a BCS-superconductor (SC) to two normal Fermi liquid leads. The necessary mechanism to separate the two electrons coming from the same Cooper pair (spin-singlet) is achieved by coupling the SC to leads with a finite resistance. The resulting dynamical Coulomb blockade effect, which we describe phenomenologically in terms of an electromagnetic environment, is shown to be enhanced for tunneling of two spin-entangled electrons into the same lead compared to the process where the pair splits and each electron tunnels into a different lead. On the other hand in the pair-split process, the spatial correlation of a Cooper pair leads to a current suppression as a function of distance between the two tunnel junctions which is weaker for effectively lower dimensional SCs.Comment: 5 pages, 2 figure

Ballistic transport in graphene antidot lattices

Graphene samples can have a very high carrier mobility if influences from the substrate and the environment are minimized. Embedding a graphene sheet into a heterostructure with hexagonal boron nitride (hBN) on both sides was shown to be a particularly efficient way of achieving a high bulk mobility. Nanopatterning graphene can add extra damage and drastically reduce sample mobility by edge disorder. Preparing etched graphene nanostructures on top of an hBN substrate instead of SiO2 is no remedy, as transport characteristics are still dominated by edge roughness. Here we show that etching fully encapsulated graphene on the nanoscale is more gentle and the high mobility can be preserved. To this end, we prepared graphene antidot lattices where we observe magnetotransport features stemming from ballistic transport. Due to the short lattice period in our samples we can also explore the boundary between the classical and the quantum transport regime

Phase Coherent Transport in Graphene Nanoribbons and Graphene Nanoribbon Arrays

We have experimentally investigated quantum interference corrections to the conductivity of graphene nanoribbons at temperatures down to 20 mK studying both weak localization (WL) and universal conductance fluctuations (UCF). Since in individual nanoribbons at millikelvin temperatures the UCFs strongly mask the weak localization feature we employ both gate averaging and ensemble averaging to suppress the UCFs. This allows us to extract the phase coherence length from both WL and UCF at all temperatures. Above 1 K, the phase coherence length is suppressed due to Nyquist scattering whereas at low temperatures we observe a saturation of the phase coherence length at a few hundred nanometers, which exceeds the ribbon width, but stays below values typically found in bulk graphene. To better describe the experiments at elevated temperatures, we extend the formula for 1D weak localization in graphene, which was derived in the limit of strong intervalley scattering, to include all elastic scattering rates.Comment: 8 pages, 6 figures, accepted by PR

Electronic properties of a graphene antidot in magnetic fields

We report on several unusual properties of a graphene antidot created by a piecewise constant potential in a magnetic field. We find that the total probability of finding the electron in the barrier can be nearly one while it is almost zero outside the barrier. In addition, for each electron state of a graphene antidot there is a dot state with exactly the same wavefunction but with a different energy. This symmetry is a consequence of Klein tunneling of Dirac electrons. Moreover, in zigzag nanoribbons we find strong coupling between some antidot states and zigzag edge states. Experimental tests of these effects are proposed