Maciej.bazarnik

Article

Wrinkles in graphene can restrict the motion of electrons to one dimension. Here, the authors observe a one-dimensional van Hove singularity and bandgap opening in a five nanometre wide wrinkle, which enables them to create a metallic-semiconducting-metallic junction in a single graphene sheet.

Nature Communications doi: 10.1038/ncomms9601

Authors: Hyunseob Lim, Jaehoon Jung, Rodney S. Ruoff, Yousoo Kim

Abstract

Nature Materials 14, 981 (2015). doi:10.1038/nmat4361

Authors: Manuel Gruber, Fatima Ibrahim, Samy Boukari, Hironari Isshiki, Loïc Joly, Moritz Peter, Michał Studniarek, Victor Da Costa, Hashim Jabbar, Vincent Davesne, Ufuk Halisdemir, Jinjie Chen, Jacek Arabski, Edwige Otero, Fadi Choueikani, Kai Chen, Philippe Ohresser, Wulf Wulfhekel, Fabrice Scheurer, Wolfgang Weber, Mebarek Alouani, Eric Beaurepaire & Martin Bowen

Molecular semiconductors may exhibit antiferromagnetic correlations well below room temperature. Although inorganic antiferromagnetic layers may exchange bias single-molecule magnets, the reciprocal effect of an antiferromagnetic molecular layer magnetically pinning an inorganic ferromagnetic layer through exchange bias has so far not been observed. We report on the magnetic interplay, extending beyond the interface, between a cobalt ferromagnetic layer and a paramagnetic organic manganese phthalocyanine (MnPc) layer. These ferromagnetic/organic interfaces are called spinterfaces because spin polarization arises on them. The robust magnetism of the Co/MnPc spinterface stabilizes antiferromagnetic ordering at room temperature within subsequent MnPc monolayers away from the interface. The inferred magnetic coupling strength is much larger than that found in similar bulk, thin or ultrathin systems. In addition, at lower temperature, the antiferromagnetic MnPc layer induces an exchange bias on the Co film, which is magnetically pinned. These findings create new routes towards designing organic spintronic devices.

Nature Materials 14, 1020 (2015). doi:10.1038/nmat4384

Authors: Feng-feng Zhu, Wei-jiong Chen, Yong Xu, Chun-lei Gao, Dan-dan Guan, Can-hua Liu, Dong Qian, Shou-Cheng Zhang & Jin-feng Jia

Nature Nanotechnology 10, 761 (2015). doi:10.1038/nnano.2015.156

Authors: V. E. Calado, S. Goswami, G. Nanda, M. Diez, A. R. Akhmerov, K. Watanabe, T. Taniguchi, T. M. Klapwijk & L. M. K. Vandersypen

Hybrid graphene–superconductor devices have attracted much attention since the early days of graphene research. So far, these studies have been limited to the case of diffusive transport through graphene with poorly defined and modest-quality graphene/superconductor interfaces, usually combined with small critical magnetic fields of the superconducting electrodes. Here, we report graphene-based Josephson junctions with one-dimensional edge contacts of molybdenum rhenium. The contacts exhibit a well-defined, transparent interface to the graphene, have a critical magnetic field of 8 T at 4 K, and the graphene has a high quality due to its encapsulation in hexagonal boron nitride. This allows us to study and exploit graphene Josephson junctions in a new regime, characterized by ballistic transport. We find that the critical current oscillates with the carrier density due to phase-coherent interference of the electrons and holes that carry the supercurrent caused by the formation of a Fabry–Pérot cavity. Furthermore, relatively large supercurrents are observed over unprecedented long distances of up to 1.5 μm. Finally, in the quantum Hall regime we observe broken symmetry states while the contacts remain superconducting. These achievements open up new avenues to exploit the Dirac nature of graphene in interaction with the superconducting state.

Author(s): Olesia Snezhkova, Johann Lüder, Alissa Wiengarten, Shiri R. Burema, Felix Bischoff, Yuanqin He, Jan Rusz, Jan Knudsen, Marie-Laure Bocquet, Knud Seufert, Johannes V. Barth, Willi Auwärter, Barbara Brena, and Joachim Schnadt

Subtle changes in the geometric and electronic properties of supported molecules, with a potential impact on the functioning of molecular devices, can typically be imaged by scanning probe microscopy, but their exact origin and nature often remain unclear. Here we show explicitly that the symmetry r…

[Phys. Rev. B 92, 075428] Published Wed Aug 19, 2015

Author(s): F. Albrecht, J. Repp, M. Fleischmann, M. Scheer, M. Ondráček, and P. Jelínek

A new scanning-probe-microscopy technique can image the polarity of individual chemical bonds.

[Phys. Rev. Lett. 115, 076101] Published Thu Aug 13, 2015

Article

Separation and analysis of enantiomers is a difficult task due to the normally identical physical properties they display. Here, the authors show how chiral molecules with non-zero dipoles can be propelled in opposite directions under the influence of a rotating electric field.

Nature Communications doi: 10.1038/ncomms8868

Authors: Jonathon B. Clemens, Osman Kibar, Mirianas Chachisvilis

Author(s): Wei Liu, Friedrich Maaß, Martin Willenbockel, Christopher Bronner, Michael Schulze, Serguei Soubatch, F. Stefan Tautz, Petra Tegeder, and Alexandre Tkatchenko

Interfaces between organic molecules and solid surfaces play a prominent role in heterogeneous catalysis, molecular sensors and switches, light-emitting diodes, and photovoltaics. The properties and the ensuing function of such hybrid interfaces often depend exponentially on molecular adsorption hei…

[Phys. Rev. Lett. 115, 036104] Published Fri Jul 17, 2015

We develop a quantum mechanical formalism to treat the strong coupling between an electromagnetic mode and a vibrational excitation of an ensemble of organic molecules. By employing a Bloch–Redfield–Wangsness approach, we show that the influence of dephasing-type interactions, i.e., elastic collisions with a background bath of phonons, critically depends on the nature of the bath modes. In particular, for long-range phonons corresponding to a common bath, the dynamics of the ‘bright state’ (the collective superposition of molecular vibrations coupling to the cavity mode) is effectively decoupled from other system eigenstates. For the case of independent baths (or short-range phonons), incoherent energy transfer occurs between the bright state and the uncoupled dark states. However, these processes are suppressed when the Rabi splitting is larger than the frequency range of the bath modes, as achieved in a recent experiment (Shalabney et al 2015 Nat. Commun. [...]

Semiconducting graphene nanoribbons (GNRs) are envisioned to play an important role in future electronics. This requires the GNRs to be placed on a surface where they may become strained. Theory predicts that axial strain, i.e. in-plane bending of the GNR, will cause a change in the band gap of the GNR. This may negatively affect device performance. Using the tip of a scanning tunneling microscope we controllably bent and buckled atomically well-defined narrow armchair GNR and subsequently probed the changes in the local density of states. These experiments show that the band gap of 7-ac-GNR is very robust to in-plane bending and out-of-plane buckling.

Nature Physics 11, 421 (2015). doi:10.1038/nphys3265

Authors: S. Dal Conte, L. Vidmar, D. Golež, M. Mierzejewski, G. Soavi, S. Peli, F. Banfi, G. Ferrini, R. Comin, B. M. Ludbrook, L. Chauviere, N. D. Zhigadlo, H. Eisaki, M. Greven, S. Lupi, A. Damascelli, D. Brida, M. Capone, J. Bonča, G. Cerullo & C. Giannetti

Nature Physics 11, 398 (2015). doi:10.1038/nphys3302

Authors: Boris Dzyubenko, Hao-Chun Lee, Oscar E. Vilches & David H. Cobden

A single-walled carbon nanotube presents a seamless cylindrical graphene surface and is thus an ideal adsorption substrate for investigating the physics of atoms and molecules in two dimensions and approaching the one-dimensional limit. When a suspended nanotube is made into a transistor, frequency shifts of its mechanical resonances allow precise measurement of the adsorbed mass down to the single-atom level. Here we show that its electrical characteristics are also modified by the adsorbed atoms and molecules, partly as a result of a small charge transfer between them and the carbon surface. We quantify this charge transfer, finding it similar for many different species, and use the associated sensitivity of the conductance to carry out the studies of phase transitions, critical scaling, dynamical fluctuations and dissipative metastable states in a system of interacting atoms confined to a cylindrical geometry.

Article

Three-dimensional topological insulators are materials that are nonmagnetic insulators in the bulk but exhibit metallic surface states. Yoshimi et al , now identify a signature of such two-dimensional states, the quantum Hall effect, in bismuth-based chalcogenide topological insulators.

Nature Communications doi: 10.1038/ncomms7627

Authors: R. Yoshimi, A. Tsukazaki, Y. Kozuka, J. Falson, K.S. Takahashi, J.G. Checkelsky, N. Nagaosa, M. Kawasaki, Y. Tokura