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“Klein paradox for a pn junction in multilayer graphene”. Van Duppen B, Peeters FM, Europhysics letters 102, 27001 (2013). http://doi.org/10.1209/0295-5075/102/27001
Abstract: Charge carriers in single and multilayered graphene systems behave as chiral particles due to the particular lattice symmetry of the crystal. We show that the interplay between the meta-material properties of graphene multilayers and the pseudospinorial properties of the charge carriers result in the occurrence of Klein and anti-Klein tunneling for rhombohedral stacked multilayers. We derive an algebraic formula predicting the angles at which these phenomena occur and support this with numerical calculations for systems up to four layers. We present a decomposition of an arbitrarily stacked multilayer into pseudospin doublets that have the same properties as rhombohedral systems with a lower number of layers. Copyright (C) EPLA, 2013
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.957
Times cited: 17
DOI: 10.1209/0295-5075/102/27001
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“Nanofilms as quantum-engineered multiband superconductors : the Ginzburg-Landau theory”. Shanenko AA, Orlova NV, Vagov A, Milošević, MV, Axt VM, Peeters FM, Europhysics letters 102, 27003 (2013). http://doi.org/10.1209/0295-5075/102/27003
Abstract: Recently fabricated single-crystalline atomically flat metallic nanofilms are in fact quantum-engineered multiband superconductors. Here the multiband structure is dictated by the nanofilm thickness through the size quantization of the electron motion perpendicular to the nanofilm. This opens the unique possibility to explore superconductivity in well-controlled multi-band systems. However, a serious obstacle is the absence of a convenient and manageable theoretical tool to access new physical phenomena in such quasi-two-dimensional systems, including interplay of quantum confinement and fluctuations. Here we cover this gap and construct the appropriate multiband Ginzburg-Landau functional for nano-thin superconductors. Copyright (C) EPLA, 2013
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.957
Times cited: 8
DOI: 10.1209/0295-5075/102/27003
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“Spin effects in electron vortex states”. Van Boxem R, Verbeeck J, Partoens B, Europhysics letters 102, 40010 (2013). http://doi.org/10.1209/0295-5075/102/40010
Abstract: The recent experimental realization of electron vortex beams opens up a wide research domain previously unexplored. The present paper explores the relativistic properties of these electron vortex beams, and quantifies deviations from the scalar wave theory. It is common in electron optics to use the Schrodinger equation neglecting spin. The present paper investigates the role of spin and the total angular momentum J(z) and how it pertains to the vortex states. As an application, we also investigate if it is possible to use holographic reconstruction to create novel total angular momentum eigenstates in a transmission electron microscope. It is demonstrated that relativistic spin coupling effects disappear in the paraxial limit, and spin effects in holographically created electron vortex beams can only be exploited by using specialized magnetic apertures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 1.957
Times cited: 11
DOI: 10.1209/0295-5075/102/40010
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“Anharmonic effects on thermodynamic properties of a graphene monolayer”. da Silva ALC, Candido L, Teixeira Rabelo JN, Hai G-Q, Peeters FM, Europhysics letters 107, 56004 (2014). http://doi.org/10.1209/0295-5075/107/56004
Abstract: We extend the unsymmetrized self-consistent-field method (USF) for anharmonic crystals to layered non-Bravais crystals to investigate structural, dynamical and thermodynamic properties of a free-standing graphene monolayer. In this theory, the main anharmonicity of the crystal lattice has been included and the quantum corrections are taken into account in an h-expansion for the one-particle density matrix. The obtained result for the thermal expansion coefficient (TEC) of graphene shows a strong temperature dependence and agrees with experimental results by Bao et al. (Nat. Nanotechnol., 4 (2009) 562). The obtained value of TEC at room temperature (300 K) is -6.4 x 10(- 6) K- 1 and it becomes positive for T > T-alpha = 358K. We find that quantum effects are significant for T < 1000 K. The interatomic distance, effective amplitudes of the graphene lattice vibrations, adiabatic and isothermal bulk moduli, isobaric and isochoric heat capacities are also calculated and their temperature dependences are determined. Copyright (C) EPLA, 2014
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.957
Times cited: 23
DOI: 10.1209/0295-5075/107/56004
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“Direct structural and spectroscopic investigation of ultrathin films of tetragonal CuO: Six-fold coordinated copper”. Samal D, Tan H, Takamura Y, Siemons W, Verbeeck J, Van Tendeloo G, Arenholz E, Jenkins CA, Rijnders G, Koster G, Europhysics letters 105, 17003 (2014). http://doi.org/10.1209/0295-5075/105/17003
Abstract: Unlike other 3d transition metal monoxides (MnO, FeO, CoO, and NiO), CuO is found in a low-symmetry distorted monoclinic structure rather than the rocksalt structure. We report here of the growth of ultrathin CuO films on SrTiO3 substrates; scanning transmission electron microscopy was used to show the stabilization of a tetragonal rocksalt structure with an elongated c-axis such that c/a similar to 1.34 and the Cu-O-Cu bond angle similar to 180 degrees, pointing to metastable six-fold coordinated Cu. X-ray absorption spectroscopy demonstrates that the hole at the Cu site for the CuO is localized in 3d(x2-y2) orbital unlike the well-studied monoclinic CuO phase. The experimental confirmation of the tetragonal structure of CuO opens up new avenues to explore electronic and magnetic properties of six-fold coordinated Cu. Copyright (C) EPLA, 2014
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.957
Times cited: 15
DOI: 10.1209/0295-5075/105/17003
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“Vortex-antivortex dynamics in mesoscopic symmetric and asymmetric superconducting loops with an applied ac current”. Zha G-Q, Peeters FM, Zhou S-P, Europhysics letters 108, 57001 (2014). http://doi.org/10.1209/0295-5075/108/57001
Abstract: In the framework of the time-dependent Ginzburg-Landau formalism, we study the dynamics of vortex-antivortex (V-Av) pairs in mesoscopic symmetric and asymmetric superconducting loops under an applied ac current. In contrast to the case of a constant biasing dc current, the process of the V-Av collision and annihilation is strongly affected by the time-periodic ac signal. As the direction of the applied ac current is reversed, the existed V-Av pair moves backward and then collides with a new created Av-V pair in a symmetric loop. In the presence of an appropriate external magnetic field, a novel sinusoidal-like oscillatory mode of the magnetization curve is observed, and the periodic dynamical process of the V-Av annihilation occurs in both branches of the sample. Moreover, for the asymmetric sample with an off-centered hole the creation point of the V-Av pair shifts away from the center of the sample, and the creation and annihilation dynamics of V-Av pairs turns out to be very different from the symmetric case. Copyright (C) EPLA, 2014
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.957
Times cited: 4
DOI: 10.1209/0295-5075/108/57001
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“Position-dependent effect of non-magnetic impurities on superconducting properties of nanowires”. Zhang L-F, Covaci L, Peeters FM, Europhysics letters 109, 17010 (2015). http://doi.org/10.1209/0295-5075/109/17010
Abstract: Anderson's theorem states that non-magnetic impurities do not change the bulk properties of conventional superconductors. However, as the dimensionality is reduced, the effect of impurities becomes more significant. Here we investigate superconducting nanowires with diameter comparable to the Fermi wavelength $\lambda_F$ (which is less than the superconducting coherence length) by using a microscopic description based on the Bogoliubov-de Gennes method. We find that: 1) impurities strongly affect the superconducting properties, 2) the effect is impurity position dependent, and 3) it exhibits opposite behavior for resonant and off-resonant wire widths. We show that this is due to the interplay between the shape resonances of the order parameter and the subband energy spectrum induced by the lateral quantum confinement. These effects can be used to manipulate the Josephson current, filter electrons by subband and investigate the symmetries of the superconducting subband gaps.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.957
Times cited: 7
DOI: 10.1209/0295-5075/109/17010
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“Equivalence of 3D bipolarons in a strong magnetic field to 1D bipolarons”. Smondyrev MA, Kochetov EA, Verbist G, Peeters FM, Devreese JT, Europhysics letters 19, 519 (1992). http://doi.org/10.1209/0295-5075/19/6/013
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Theory of quantum systems and complex systems
Impact Factor: 2.095
Times cited: 17
DOI: 10.1209/0295-5075/19/6/013
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“Order, disorder and structure of crystals C60/C70”. Bohr J, Gibbs D, Sinha SK, Krätschmer W, Van Tendeloo G, Larsen E, Egsgaard H, Berman LE, Europhysics letters 17, 327 (1992). http://doi.org/10.1209/0295-5075/17/4/008
Abstract: Single crystals with two different morphologies, black and brown, of C60 with about 12% C70 have been studied by synchrotron X-ray diffraction. Integrated intensities from 8 reflections show that the charge distribution of the C60 cluster is shell-like giving rise to an oscillatory behaviour in the diffracted intensities. From the intensities, the distance between diametrically opposite carbon atoms has been determined to be (7.24 +/- 0.22) angstrom. The thickness of the charge distribution of the shell can be estimated as 3.06 angstrom and the cavity within a C60 cluster to have a diameter of about 4.18 angstrom. The finite longitudinal width of the diffraction peaks from black crystals indicates a lack of long-range crystalline order. The rocking curves are about 7-degrees broad and depict an unusually smooth behaviour. This may be indicative of a glassy or hexatic phase. High-resolution electron microscopy allows small crystallites with a relatively well-defined orientation relationship to be identified. In contrast, brown crystals have long-range order.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.095
Times cited: 15
DOI: 10.1209/0295-5075/17/4/008
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“The texture of catalytically grown coil-shaped carbon nanotubes”. Zhang XB, Zhang XF, Bernaerts D, Van Tendeloo G, Amelinckx S, van Landuyt J, Ivanov V, Nagy JB, Lambin P, Lucas AA, Europhysics letters 27, 141 (1994). http://doi.org/10.1209/0295-5075/27/2/011
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.095
Times cited: 168
DOI: 10.1209/0295-5075/27/2/011
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