Alexandre Smogunov's Home Page

2017 P. Giannozzi et al.,
Advanced capabilities for materials modelling with Quantum ESPRESSO,
J. Phys.: Condens. Matter 29, 465901 (2017)

Qian Zhang, Shuhui Tao, Ruowei Yi, Chunhui He, Cezhou Zhao, Weitao Su, Alexander Smogunov, Yannick J. Dappe, Richard J. Nichols, Li Yang,
Symmetry Effects on Attenuation Factors in Graphene-Based Molecular Junctions,
J. Phys. Chem. Lett. 8, 5987 (2017)

V. D. Pham, V. Repain, C. Chacon, A. Bellec, Y. Girard, S. Rousset, E. Abad, Y. J. Dappe, A. Smogunov and J. Lagoute,
Tuning the Electronic and Dynamical Properties of a Molecule by Atom Trapping Chemistry,
ACS Nano 11, 10742 (2017)

D. Di Felice, E. Abad, C. González, A. Smogunov and Y.J. Dappe,
Angle dependence of the local electronic properties of the graphene/MoS2 interface determined by ab initio calculations,
J. Phys. D: Appl. Phys. 50, 17LT02 (2017)

2016 D. Li, C. Barreteau, S. L. Kawahara, J. Lagoute, C. Chacon, Y. Girard, S. Rousset, V. Repain, and A. Smogunov,
Symmetry-selected spin-split hybrid states in C60/ferromagnetic interfaces,
Phys. Rev. B 93, 085425 (2016)

D. Li, C. Barreteau and A. Smogunov,
Magnetocrystalline anisotropy of Fe and Co slabs and clusters on SrTiO3 by first-principles,
Phys. Rev. B 93, 144405 (2016)

V. D. Pham, V. Repain, C. Chacon, A. Bellec, Y. Girard, S. Rousset, A. Smogunov, Y.J. Dappe and J. Lagoute,
Control of Molecule-Metal Interaction by Hydrogen Manipulation in an Organic Molecule,
J. Phys. Chem. Lett. 7(8), 1416 (2016)

D. Li, Y. J. Dappe and A. Smogunov,
Perfect spin filtering by symmetry in molecular junctions,
Phys. Rev. B 93, 201403(R) (2016)

K. Bairagi, O. Iasco, A. Bellec, A. Kartsev, D. Li, J. Lagoute, C. Chacon, Y. Girard, S. Rousset, F. Miserque, Y.J. Dappe, A. Smogunov, C. Barreteau, M.-L. Boillot, T. Mallah and V. Repain,
Molecular scale dynamics of light-induced spin crossover in a two-dimensional layer,
Nature Communications 7, 12212 (2016)

R. Requist, P. P. Baruselli, A. Smogunov, M. Fabrizio, S. Modesti, E. Tosatti,
Metallic, magnetic and molecular nanocontacts,
Nature Nanotechnology 11, 499 (2016)

2015 P. P. Baruselli, R. Requist, A. Smogunov, M. Fabrizio, and E. Tosatti,
Co adatoms on Cu surfaces: Ballistic conductance and Kondo temperature,
Phys. Rev. B 92, 045119 (2015), (DOI: http://dx.doi.org/10.1103/PhysRevB.92.045119).

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The Kondo zero-bias anomaly of Co adatoms probed by scanning tunneling microscopy is known to depend on the height of the tip above the surface, and this dependence is different on different low index Cu surfaces. On the (100) surface, the Kondo temperature first decreases then increases as the tip approaches the adatom, while on the (111) surface it is virtually unaffected. These trends are captured by combined density functional theory and numerical renormalization-group calculations. The adatoms are found to be described by an S=1 Anderson model on both surfaces, and ab initio calculations help identify the symmetry of the active d orbitals. We correctly reproduce the Fano line shape of the zero-bias anomaly for Co/Cu(100) in the tunneling regime but not in the contact regime, where it is probably dependent on the details of the tip and contact geometry. The line shape for Co/Cu(111) is presumably affected by the presence of surface states, which are not included in our method. We also discuss the role of symmetry, which is preserved in our model scattering geometry but most likely broken in experimental conditions.

K. Bairagi et al.,
Tuning the Magnetic Anisotropy at a Molecule-Metal Interface,
Phys. Rev. Lett. 114, 247203 (2015), (DOI: 10.1103/PhysRevLett.114.247203).

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We demonstrate that a C60 overlayer enhances the perpendicular magnetic anisotropy of a Co thin film, inducing an inverse spin reorientation transition from in plane to out of plane. The driving force is the C60/Co interfacial magnetic anisotropy that we have measured quantitatively in situ as a function of the C60 coverage. Comparison with state-of-the-art ab initio calculations show that this interfacial anisotropy mainly arises from the local hybridization between C60 p_z and Co d_z2 orbitals. By generalizing these arguments, we also demonstrate that the hybridization of C60 with a Fe(110) surface decreases the perpendicular magnetic anisotropy. These results open the way to tailor the interfacial magnetic anisotropy in organic-material–ferromagnet systems.

A. Smogunov, Y. J. Dappe,
Symmetry-Derived Half-Metallicity in Atomic and Molecular Junctions,
Nano Lett. 15, 3552 (2015), (DOI: 10.1021/acs.nanolett.5b01004).

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Achieving highly spin-polarized electric currents in atomic-scale junctions is of great importance in the field of nanoelectronics and spintronics. Based on robust symmetry considerations, we propose a mechanism to block completely one of spin conduction channels for a broad class of atomic and molecular junctions bridging two ferromagnetic electrodes. This particular behaviour is due to the wave-function orthogonality between spin up s-like states in ferromagnetic electrode and available π-channels in the junction. As a consequence, the system would ideally yield 100 % spin-polarized current, with a junction acting thus as a "half-metallic" conductor. Using ab initio electron transport calculations, we demonstrate this principle on two examples: i) a short carbon chain and ii) a π-conjugated molecule (polythiophene) connected either to model semi-infinite Ni wires or to realistic Ni(111) electrodes. It is also predicted that such atomic-scale junctions should lead to very high (ideally, infinite) magneto-resistance ratios since the electric current gets fully blocked if two electrodes have anti-parallel magnetic alignment.

P. Yang et al.,
C-60 as an Atom Trap to Capture Co Adatoms,
JOURNAL OF PHYSICAL CHEMISTRY C 119, 6873 (2015), (DOI: 10.1021/jp512723c).

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C60 molecules were used to trap Co adatoms and clusters on a Au(111) surface using atomic/molecular manipulation with a scanning tunneling microscope. Two manipulation pathways (successive integration of single Co atoms in one molecule or direct integration of a Co cluster) were found to efficiently allow the formation of complexes mixing a C60 molecule with Co atoms. Scanning tunneling spectroscopy reveals the robustness of the π states of C60 that are preserved after Co trapping. Scanning tunneling microscopy images and density functional theory calculations reveal that dissociated Co clusters of up to nine atoms can be formed at the molecule-substrate interface. These results open new perspectives in the interactions between metal adatoms and molecules, for applications in metal-organic devices.

2014 D. Li, C. Barreteau, M. R. Castell, F. Silly, A. Smogunov,
Out- versus in-plane magnetic anisotropy of free Fe and Co nanocrystals: Tight-binding and first-principles studies,
Phys. Rev. B 90, 205409 (2014), (DOI: 10.1103/PhysRevB.90.205409).

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We report tight-binding and density functional theory calculations of magnetocrystalline anisotropy energy (MAE) of free Fe (body-centered-cubic) and Co (face-centered-cubic) slabs and nanocrystals. The nanocrystals are truncated square pyramids which can be grown experimentally by deposition of metal on a SrTiO3(001) substrate. For both elements our local analysis shows that the total MAE of the nanocrystals is largely dominated by the contribution of (001) facets. However, while the easy axis of Fe(001) is out-of-plane, it is in-plane for Co(001). This has direct consequences on the magnetic reversal mechanism of the nanocrystals. Indeed, the very high uniaxial anisotropy of Fe nanocrystals makes them a much better potential candidate for magnetic storage devices.

R. Requist, S. Modesti, P.P. Baruselli, A. Smogunov, M. Fabrizio, E. Tosatti,
Kondo conductance across the smallest spin 1/2 radical molecule,
PNAS 111, 69 (2014), (DOI: 10.1073/pnas.1322239111).

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Molecular contacts are generally poorly conducting because their energy levels tend to lie far from the Fermi energy of the metal contact, necessitating undesirably large gate and bias voltages in molecular electronics applications. Molecular radicals are an exception because their partly filled orbitals undergo Kondo screening, opening the way to electron passage even at zero bias. Whereas that phenomenon has been experimentally demonstrated for several complex organic radicals, quantitative theoretical predictions have not been attempted so far. It is therefore an open question whether and to what extent an ab initio-based theory is able to make accurate predictions for Kondo temperatures and conductance lineshapes. Choosing nitric oxide (NO) as a simple and exemplary spin 1/2 molecular radical, we present calculations based on a combination of density functional theory and numerical renormalization group (DFT+NRG), predicting a zero bias spectral anomaly with a Kondo temperature of 15 K for NO/Au(111). A scanning tunneling spectroscopy study is subsequently carried out to verify the prediction, and a striking zero bias Kondo anomaly is confirmed, still quite visible at liquid nitrogen temperatures. Comparison shows that the experimental Kondo temperature of about 43 K is larger than the theoretical one, whereas the inverted Fano lineshape implies a strong source of interference not included in the model. These discrepancies are not a surprise, providing in fact an instructive measure of the approximations used in the modeling, which supports and qualifies the viability of the density functional theory and numerical renormalization group approach to the prediction of conductance anomalies in larger molecular radicals.

M. Viciano-Chumillas et al.,
Tailoring the Structure of Two-Dimensional Self-Assembled Nanoarchitectures Based on NiII-Salen Building Blocks,
Chemistry: A European Journal 20, 13566 (2014).

2013
P. P. Baruselli, M. Fabrizio, A. Smogunov, R. Requist, and E. Tosatti,
Magnetic impurities in nanotubes: From density functional theory to Kondo many-body effects,
Phys. Rev. B 88, 245426 (2013) (arXiv:1401.1392).

M. Kumar, O. Tal, R. H. M. Smit, A. Smogunov, E. Tosatti, J. M. van Ruitenbeek,
Shot noise and magnetism of Pt atomic chains: Accumulation of points at the boundary,
Phys. Rev. B 88, 245431 (2013).

P. V. Lukashev, J. D. Burton, A. Smogunov, J. P. Velev, E. Y. Tsymbal,
Interface states in CoFe2O4 spin-filter tunnel junctions,
Phys. Rev. B 88, 134430 (2013) (arXiv:1308.3461).

D. Li, A. Smogunov, C. Barreteau, F. Ducastelle, D. Spanjaard,
Magnetocrystalline anisotropy energy of Fe(001) and Fe(110) slabs and nanoclusters: A detailed local analysis within a tight-binding model,
Phys. Rev. B 88, 214413 (2013) (arXiv:1309.4578).

P. Habibi, C. Barreteau, A. Smogunov,
Electronic and magnetic structure of the Cr(001) surface,
J. Phys.: Condens. Matter 25, 146002 (2013).

2012
S. L. Kawahara, J. Lagoute, V. Repain, C. Chacon, Y. Girard, S. Rousset, A. Smogunov, and C. Barreteau,
Large Magnetoresistance through a Single Molecule due to a Spin-Split Hybridized Orbital,
Nano Lett. 12, 4558 (2012), (DOI: 10.1021/nl301802e).

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Using organic materials in spintronic devices raises a lot of expectation for future applications due to their flexibility, low cost, long spin lifetime, and easy functionalization. However, the interfacial hybridization and spin polarization between the organic layer and the ferromagnetic electrodes still has to be understood at the molecular scale. Coupling state-of-the-art spin-polarized scanning tunneling spectroscopy and spin-resolved ab initio calculations, we give the first experimental evidence of the spin splitting of a molecular orbital on a single non magnetic C60 molecule in contact with a magnetic material, namely, the Cr(001) surface. This hybridized molecular state is responsible for an inversion of sign of the tunneling magnetoresistance depending on energy. This result opens the way to spin filtering through molecular orbitals.

P.-P. Baruselli, A. Smogunov, M. Fabrizio, E. Tosatti,
Kondo Effect of Magnetic Impurities in Nanotubes,
Phys. Rev. Lett. 108, 206807 (2012) (arXiv:1201.3301).

G. Sclauzero, A. Dal Corso, A. Smogunov,
Interaction of CO with an Au monatomic chain at different strains: Electronic structure and ballistic transport,
Phys. Rev. B 85, 165411 (2012) (arXiv:1203.4712).

G. Sclauzero, A. Dal Corso, A. Smogunov,
Effect of stretching on the ballistic conductance of Au nanocontacts in presence of CO: A density functional study,
Phys. Rev. B 85, 165412 (2012) (arXiv:1203.4713).

2010 P. Gava, A. Dal Corso, A. Smogunov, E. Tosatti,
Magnetism-induced ballistic conductance changes in palladium nanocontacts,
EUROPEAN PHYSICAL JOURNAL B 75, 57 (2010).

2009
P. Lucignano, R. Mazzarello, A. Smogunov, M. Fabrizio, E. Tosatti,
Kondo conductance in an atomic nanocontact from first principles,
Nature Materials 8, 563 (2009).

J. Velev, C.-G. Duan, J. Burton, A. Smogunov, M. Niranjan, E. Tosatti, S. Jaswal, E. Tsymbal,
Magnetic tunnel junctions with ferroelectric barriers: Prediction of four resistance states from first-principles,
Nano Lett. 9, 427 (2009) (arXiv:0812.2393).

P. Giannozzi et al.,
QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials,
J. Phys. Condens. Matter 21, 395502 (2009).

2008 A. Smogunov, A. Dal Corso, A. Delin, R. Weht, E. Tosatti,
Colossal magnetic anisotropy of monatomic free and deposited platinum nanowires,
Nature Nanotechnology 3, 22-25 (2008).

Y. Miura, R. Mazzarello, A. Dal Corso, A. Smogunov, E. Tosatti,
Monatomic Au wire with a magnetic Ni impurity: Electronic structure and ballistic conductance,
Phys. Rev. B 78, 205412 (2008).

G. Sclauzero, A. Dal Corso, A. Smogunov, E. Tosatti,
Interaction of a CO molecule with a Pt monatomic wire: Electronic structure and ballistic conductance,
Phys. Rev. B 78, 085421 (2008) (arXiv:0809.0644).

A. Smogunov, A. Dal Corso, E. Tosatti,
Magnetic phenomena, spin-orbit effects, and electron transport in Pt nanowire contacts,
Phys. Rev. B 78, 014423 (2008) (arXiv:0804.3340).

2006 A. Dal Corso, A. Smogunov, E. Tosatti,
Ab initio ballistic conductance with spin-orbit coupling: Application to monoatomic wires,
Phys. Rev. B 74, 045429 (2006).

A. Smogunov, A. Dal Corso, E. Tosatti,
Ballistic conductance and magnetism in short tip suspended Ni nanowires,
Phys. Rev. B 73, 075418 (2006) (arXiv:cond-mat/0601608).

2004 A. Smogunov, A. Dal Corso, E. Tosatti,
Ballistic conductance of magnetic Co and Ni nanowires with ultrasoft pseudo-potentials,
Phys. Rev. B 70, 045417 (2004) (arXiv:cond-mat/0405433).

A. Smogunov, A. Dal Corso, E. Tosatti,
Ballistic conductance of Ni nanowire with a magnetization reversal,
Surf. Sci. 566-568, 390 (2004) (arXiv:cond-mat/0310335).

< 2004 F. Picaud, A. Smogunov, A. Dal Corso, E. Tosatti,
Complex Band Structures and Decay Length in Polyethylene Chains,
J. Phys.: Condens. Matter 15, 3731-3740, (2003) (arXiv:cond-mat/0305308).

A. Smogunov, A. Dal Corso, E. Tosatti,
Complex band structure with ultrasoft pseudopotentials: fcc Ni and Ni nanowire,
Surf. Sci. 532-535, 549-555, (2003) (arXiv:cond-mat/0302100).

A. Smogunov, A. Dal Corso, E. Tosatti,
Selective d-state conducting blocking in nickel nanocontacts,
Surf. Sci. 507-510, 609, (2002) (arXiv:cond-mat/0111376).

Smogunov A.N., Kurkina L.I., Farberovich O.V.,
Linear response of embedded simple metal threads,
Surf. Sci. 469, 133-143, (2000).

Smogunov A.N., Kurkina L.I., Farberovich O.V.,
Electronic structure and polarizability of quantum metallic wires,
Phys. Solid State 42, 1898-1907, (2000).

Smogunov A.N., Kurkina L.I., Kurganskii S.I.,
Density-functional calculations of static and dynamic polarizabilities of thready cylindrical crystals,
Surf. Sci. 421, 237-245, (1999).

Smogunov A.N., Kurkina L.I., Kurganskii S.I.,
Electronic structure of simple metal whiskers,
Surf. Sci. 391, 245-251, (1997).