References of "Morgenstern, Markus"
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See detailTuning the Pseudospin Polarization of Graphene by a Pseudomagnetic Field
Georgi, Alexander; Nemes-Incze, Peter; Carrillo-Bastos, Ramon et al

in Nano Letters (2017), 17

One of the intriguing characteristics of honeycomb lattices is the appearance of a pseudomagnetic field as a result of mechanical deformation. In the case of graphene, the Landau quantization resulting ... [more ▼]

One of the intriguing characteristics of honeycomb lattices is the appearance of a pseudomagnetic field as a result of mechanical deformation. In the case of graphene, the Landau quantization resulting from this pseudomagnetic field has been measured using scanning tunneling microscopy. Here we show that a signature of the pseudomagnetic field is a local sublattice symmetry breaking observable as a redistribution of the local density of states. This can be interpreted as a polarization of graphene’s pseudospin due to a strain induced pseudomagnetic field, in analogy to the alignment of a real spin in a magnetic field. We reveal this sublattice symmetry breaking by tunably straining graphene using the tip of a scanning tunneling microscope. The tip locally lifts the graphene membrane from a SiO2 support, as visible by an increased slope of the I(z) curves. The amount of lifting is consistent with molecular dynamics calculations, which reveal a deformed graphene area under the tip in the shape of a Gaussian. The pseudomagnetic field induced by the deformation becomes visible as a sublattice symmetry breaking which scales with the lifting height of the strained deformation and therefore with the pseudomagnetic field strength. Its magnitude is quantitatively reproduced by analytic and tight-binding models, revealing fields of 1000 T. These results might be the starting point for an effective THz valley filter, as a basic element of valleytronics. [less ▲]

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See detailMolecular structure of the H2O wetting layer on Pt(111)
Standop, Sebastian; Redinger, Alex UL; Morgenstern, Markus et al

in PHYSICAL REVIEW B (2010), 82(16),

The molecular structure of the wetting layer of ice on Pt(111) is resolved using scanning tunneling microscopy. Two structures observed previously by diffraction techniques are imaged for coverages at or ... [more ▼]

The molecular structure of the wetting layer of ice on Pt(111) is resolved using scanning tunneling microscopy. Two structures observed previously by diffraction techniques are imaged for coverages at or close to completion of the wetting layer. At 140 K only a root 37 x root 37R25.3 degrees superstructure can be established while at 130 K also a root 39 x root 39R16.1 degrees superstructure with slightly higher molecular density is formed. In the temperature range under concern the superstructures reversibly transform into each other by slight changes in coverage through adsorption or desorption. The superstructures exhibit a complex pattern of molecules in different geometries. [less ▲]

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See detailDesorption of H2O from Flat and Stepped Pt(111)
Picolin, Alexander; Busse, Carsten; Redinger, Alex UL et al

in Journal of Physical Chemistry. C, Nanomaterials and interfaces (2009), 113(2), 691-697

To investigate the effect of steps on H2O binding on a nominal Pt(111) surface, we used thermal desorption spectroscopy of water adsorbed on purposefully nanostructured surfaces: a rippled surface ... [more ▼]

To investigate the effect of steps on H2O binding on a nominal Pt(111) surface, we used thermal desorption spectroscopy of water adsorbed on purposefully nanostructured surfaces: a rippled surface containing densely packed (100)-microfaceted and (111)-microfaceted steps was created using grazing incidence ion bombardment, and a surface with triangular mounds mainly consisting of (111)-microfaceted steps was fabricated through hornoepitaxial growth. These morphologies are determined by scanning tunneling microscopy. We find two additional high -temperature H2O desorption peaks using the rippled surface, whereas only the peak with the highest desorption temperature is present on the (111)-microfaceted mound. Thus, water preferentially binds to steps and especially favors (111)-microfaceted ones. Furthermore, the large step concentration on our nanostructured surfaces precludes the coexistence of a condensed and a diluted phase in a monolayer of water and suppresses the formation of crystalline ice multilayers during heating. [less ▲]

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