Maciej.bazarnik

Abstract

Author(s): H. Vita, St. Böttcher, P. Leicht, K. Horn, A. B. Shick, and F. Máca

Using a combination of photoemission and x-ray magnetic circular dichroism (XMCD), we characterize the growth and the electronic as well as magnetic structure of cobalt layers intercalated in between graphene and Ir(111). We demonstrate that magnetic ordering exists beyond one monolayer intercalati...

[Phys. Rev. B 90, 165432] Published Wed Oct 22, 2014

Author(s): Mie Andersen, Liv Hornekær, and Bjørk Hammer

The coverage-dependent intercalation of oxygen, CO, hydrogen, alkali metals, and halogens between graphene and Ir(111) is investigated using density functional theory with van der Waals corrections. By comparing adsorption on clean Ir to intercalation we show that the presence of the graphene layer ...

[Phys. Rev. B 90, 155428] Published Thu Oct 16, 2014

Abstract

Vibrational spectroscopy in the electron microscope

Nature 514, 7521 (2014). doi:10.1038/nature13870

Authors: Ondrej L. Krivanek, Tracy C. Lovejoy, Niklas Dellby, Toshihiro Aoki, R. W. Carpenter, Peter Rez, Emmanuel Soignard, Jiangtao Zhu, Philip E. Batson, Maureen J. Lagos, Ray F. Egerton & Peter A. Crozier

Vibrational spectroscopies using infrared radiation, Raman scattering, neutrons, low-energy electrons and inelastic electron tunnelling are powerful techniques that can analyse bonding arrangements, identify chemical compounds and probe many other important properties of materials. The spatial resolution of these spectroscopies is typically one micrometre or more, although it can reach a few tens of nanometres or even a few ångströms when enhanced by the presence of a sharp metallic tip. If vibrational spectroscopy could be combined with the spatial resolution and flexibility of the transmission electron microscope, it would open up the study of vibrational modes in many different types of nanostructures. Unfortunately, the energy resolution of electron energy loss spectroscopy performed in the electron microscope has until now been too poor to allow such a combination. Recent developments that have improved the attainable energy resolution of electron energy loss spectroscopy in a scanning transmission electron microscope to around ten millielectronvolts now allow vibrational spectroscopy to be carried out in the electron microscope. Here we describe the innovations responsible for the progress, and present examples of applications in inorganic and organic materials, including the detection of hydrogen. We also demonstrate that the vibrational signal has both high- and low-spatial-resolution components, that the first component can be used to map vibrational features at nanometre-level resolution, and that the second component can be used for analysis carried out with the beam positioned just outside the sample—that is, for ‘aloof’ spectroscopy that largely avoids radiation damage.

Author(s): Sebastian Hild, Takeshi Fukuhara, Peter Schauß, Johannes Zeiher, Michael Knap, Eugene Demler, Immanuel Bloch, and Christian Gross

We study experimentally the far-from-equilibrium dynamics in ferromagnetic Heisenberg quantum magnets realized with ultracold atoms in an optical lattice. After controlled imprinting of a spin spiral pattern with an adjustable wave vector, we measure the decay of the initial spin correlations throug...

[Phys. Rev. Lett. 113, 147205] Published Fri Oct 03, 2014

Nature Physics 10, 743 (2014). doi:10.1038/nphys3075

Authors: Zhiwen Shi, Chenhao Jin, Wei Yang, Long Ju, Jason Horng, Xiaobo Lu, Hans A. Bechtel, Michael C. Martin, Deyi Fu, Junqiao Wu, Kenji Watanabe, Takashi Taniguchi, Yuanbo Zhang, Xuedong Bai, Enge Wang, Guangyu Zhang & Feng Wang

Electrons in graphene are described by relativistic Dirac–Weyl spinors with a two-component pseudospin. The unique pseudospin structure of Dirac electrons leads to emerging phenomena such as the massless Dirac cone, anomalous quantum Hall effect, and Klein tunnelling in graphene. The capability to manipulate electron pseudospin is highly desirable for novel graphene electronics, and it requires precise control to differentiate the two graphene sublattices at the atomic level. Graphene/boron nitride moiré superlattices, where a fast sublattice oscillation due to boron and nitrogen atoms is superimposed on the slow moiré period, provides an attractive approach to engineer the electron pseudospin in graphene. This unusual moiré superlattice leads to a spinor potential with unusual hybridization of electron pseudospins, which can be probed directly through infrared spectroscopy because optical transitions are very sensitive to excited state wavefunctions. Here, we perform micro-infrared spectroscopy on a graphene/boron nitride heterostructure and demonstrate that the moiré superlattice potential is dominated by a pseudospin-mixing component analogous to a spatially varying pseudomagnetic field. In addition, we show that the spinor potential depends sensitively on the gate-induced carrier concentration in graphene, indicating a strong renormalization of the spinor potential from electron–electron interactions.

Article

Individual layers of FeSe grown on SrTiO3 superconduct at far higher temperatures than in bulk, but the effect of the film-substrate interface is poorly understood. Peng et al . find that modifying this interface has a significant non-trivial effect on the superconducting characteristics of FeSe films.

Nature Communications doi: 10.1038/ncomms6044

Authors: R. Peng, H. C. Xu, S. Y. Tan, H. Y. Cao, M. Xia, X. P. Shen, Z. C. Huang, C.H.P. Wen, Q. Song, T. Zhang, B. P. Xie, X. G. Gong, D. L. Feng

Author(s): M. M. van Wijk, A. Schuring, M. I. Katsnelson, and A. Fasolino

By atomistic modeling of moiré patterns of graphene on a substrate with a small lattice mismatch, we find qualitatively different strain distributions for small and large misorientation angles, corresponding to the commensurate-incommensurate transition recently observed in graphene on hexagonal BN....

[Phys. Rev. Lett. 113, 135504] Published Tue Sep 23, 2014

Author(s): Changwon Park, Geoffrey A. Rojas, Seokmin Jeon, Simon J. Kelly, Sean C. Smith, Bobby G. Sumpter, Mina Yoon, and Petro Maksymovych

The energy scales of interactions that control molecular adsorption and assembly on surfaces can vary by several orders of magnitude, yet the importance of each contributing interaction is not apparent a priori. Tetracyanoquinodimethane (TCNQ) is an archetypal electron acceptor molecule and it is a ...

[Phys. Rev. B 90, 125432] Published Fri Sep 19, 2014

Article

Skyrmions—vortex-like spin textures—are conventionally only seen in materials that exhibit the right magnetic properties. Li et al. now create so-called artificial skyrmions using a cobalt disk embedded in a magnetized nickel film, thus presenting a platform for controlling skyrmions.

Nature Communications doi: 10.1038/ncomms5704

Authors: J. Li, A. Tan, K.W. Moon, A. Doran, M.A. Marcus, A.T. Young, E. Arenholz, S. Ma, R.F. Yang, C. Hwang, Z.Q. Qiu

Author(s): A. Sonntag, J. Hermenau, S. Krause, and R. Wiesendanger

The thermal stability of the magnetic nano-skyrmion lattice in the monolayer Fe/Ir(111) is investigated using temperature dependent spin-polarized scanning tunneling microscopy. Our experiments show that the skyrmion lattice disappears at a temperature of Tc=27.8  K, indicating a loss of long-range ...

[Phys. Rev. Lett. 113, 077202] Published Wed Aug 13, 2014

Article

Single-molecule magnets exhibit magnetic hysteresis below a certain temperature. Mannini et al . now show that grafting such molecules onto a silicon substrate can enhance their magnetic bistability.

Nature Communications doi: 10.1038/ncomms5582

Authors: Matteo Mannini, Federico Bertani, Cristina Tudisco, Luigi Malavolti, Lorenzo Poggini, Kasjan Misztal, Daniela Menozzi, Alessandro Motta, Edwige Otero, Philippe Ohresser, Philippe Sainctavit, Guglielmo G. Condorelli, Enrico Dalcanale, Roberta Sessoli

Author(s): I. Goikoetxea, J. I. Juaristi, R. Díez Muiño, and M. Alducin

We compare the adsorption dynamics of N2 on the unstrained Fe(110) and on a 10% expanded Fe monolayer grown on W(110) by performing classical molecular dynamics simulations that use potential energy surfaces calculated with density functional theory. Our results allow us to understand why, experimen...

[Phys. Rev. Lett. 113, 066103] Published Mon Aug 04, 2014

Author(s): Ran Cheng, Jiang Xiao, Qian Niu, and Arne Brataas

Spin pumping and spin-transfer torques are two reciprocal phenomena widely studied in ferromagnetic materials. However, pumping from antiferromagnets and its relation to current-induced torques have not been explored. By calculating how electrons scatter off a normal metal-antiferromagnetic interfac...

[Phys. Rev. Lett. 113, 057601] Published Tue Jul 29, 2014

Article

Understanding vertical manipulation mechanisms in atomic-force microscopy applications is a serious challenge. Here, the authors report vertical extraction and deposition processes of copper atoms at an oxidized copper surface, and rationalize the processes with a multi-step manipulation mechanism.

Nature Communications doi: 10.1038/ncomms5476

Authors: J. Bamidele, S.H. Lee, Y. Kinoshita, R. Turanský, Y. Naitoh, Y.J. Li, Y. Sugawara, I. Štich, L. Kantorovich

Article

Dynamic force spectroscopy is widely applied to probe molecular interactions by forcible bond breaking, but it currently lacks an analytical theory that spans the divide between experiment and simulation. Here, such a unified framework is developed and shown to be accurate for slow and fast loading.

Nature Communications doi: 10.1038/ncomms5463

Authors: Jakob T. Bullerjahn, Sebastian Sturm, Klaus Kroy

Nature Nanotechnology 9, 574 (2014). doi:10.1038/nnano.2014.164

Authors: Sebastian Loth, Jacob A. J. Burgess & Shichao Yan

Ultrafast, coherent spin dynamics in semiconductor heterostructures can be measured with a scanning tunnelling microscope by using femtosecond pulses of circularly polarized light.