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Gated bilayer graphene exhibits spin-degenerate gapless states with a topological character localized at stacking domain walls. These states allow for one-dimensional currents along the domain walls. We herein demonstrate that these topologically protected currents are spin-polarized and locked in a single layer when bilayer graphene contains stacking domain walls decorated with magnetic defects. The magnetic defects, which we model as π-vacancies, perturb the topological states but also lift their spin degeneracy. One gapless state survives the perturbation of these defects, and its spin polarization is largely localized in one layer. The spin-polarized current in the topological state flows in a single layer, and this finding suggests the possibility of effectively exploiting these states in spintronic applications. ; This work was partially supported by project FIS2016-76617-P of the Spanish Ministry of Economy and Competitiveness MINECO, the Basque Government under the ELKARTEK project (SUPER), and the Gobierno Vasco-UPV/EHU (Grant No. IT1246- 19). AA and WJ acknowledge the hospitality of the Institute of Physics at Nicolaus Copernicus University and the Donostia International Physics Center, respectively.

9 páginas, 5 figuras.-- El pdf del artículo es la versión pre-print. ; The magnitudes of Fe magnetic moments, together with their long-range ordering when appropriate, are compared and contrasted in a variety of metallic environments. Thus, Fe, in its stable body-centered-cubic (bcc) phase under ambient conditions, is considered under pressures p, which can yield different crystal structures at high p, including fcc. The modification of the ferromagnetism in bcc Fe is surveyed as one passes through a bc-tetragonal lattice to the fcc form. In the latter, evidence is presented, both from theory and experiment, that the ordering is antiferromagnetic in character. Then, binary metallic alloys with Fe atoms as the majority component are considered, Fe–Co and Fe–Ga being focal points in both ordered and disordered materials. Finally, some discussion is given, involving again both experiment and theory, of the possible spin polarization of neighboring Cs atoms when Fe impurity atoms are inserted into the low conduction electron density characterizing this heavy alkali metal under ambient conditions. ; Contract grant sponsor: Spanish Ministerio de Ciencia y Tecnología (MCyT), MONACEM Project. Contract grant number: Fis2007-66711-CO2-02. Contract grant sponsor: University of Basque Country. Contract grant number: IT-366-07. Contract grant sponsor: Basque Government [NANOMATERIALS Project (IE05-151), ETORTEK Program (iNanogune)]. ; Peer reviewed

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY). ; Zigzag graphene nanoribbons have spin-polarized edges, antiferromagnetically coupled in the ground state with total spin zero. Customarily, these ribbons are made ferromagnetic by producing an imbalance between the two sublattices. Here we show that zigzag ribbons can be ferromagnetic due to the presence of reconstructed divacancies near one edge. This effect takes place even though the divacancies are produced by removing two atoms from opposite sublattices, which were balanced before reconstruction to 5-8-5 defects. We demonstrate that there is a strong interaction between the defect-localized and edge bands which mix and split away from the Fermi level. This splitting is asymmetric, yielding a net edge spin polarization. Therefore, the formation of reconstructed divacancies close to the edges of the nanoribbons can be a practical way to make them partially ferromagnetic. ; This work was supported by the Polish National Science Center (Grant No. DEC-2011/03/B/ST3/00091), the Basque government through the NANOMATERIALS project (Grant No. IE05-151) under the ETORTEK Program iNanogune, the Spanish Ministry of Economy and Competitiveness MINECO (Grants No. FIS2013-48286-C2-1-P and No. FIS2012-33521), and the University of the Basque Country (Grant No. IT-366- 07). ; Peer Reviewed

Abnormally large stability of Pb nanostructures grown on metallic or semiconductor substrates has been observed even for heights of about 30 monolayers. Using both density-functional theory calculations and analytical models, we demonstrate that the stability at even higher coverages (N>30 ML) is supported by an extra second quantum beat pattern in the energetics of the metal film as a function of the number of atomic layers. This pattern is triggered by the butterflylike shape of the Fermi surface of lead in the (111) direction and supports the detection of stable magic islands of higher heights than measured up to now. ; This work was supported by the ETORTEK -NANOMAT program of the Basque government, Spanish Ministerio de Ciencia y Tecnología -MCyT of Spain -Grant No. Fis 2004-06490-CO3-00, the European Network of Excellence NANOQUANTA -NM4-CT-2004-500198 and the Intramural Special Project -Ref. 2006601242. The SGI/IZOSGIker UPV/EHU supported by the National Program for the Promotion of Human Resources within the National Plan of Scientific Research, Development and Innovation-Fondo Social Europeo, MCyT and Basque Government is gratefully acknowledged for allocation of computational resources. ; Peer reviewed

While much is known about isoelectronic materials related to carbon nanostructures, such as boron-nitride layers and nanotubes, rather less is known about equivalent silicon-based materials. Following the recent discovery of phosphorene, here we discuss isoelectronic silicon-monosulfide monolayers. We describe a set of anisotropic structures that clearly have a high stability with respect to previously reported silicon-monosulfide monolayers. The source of the layer anisotropy is related to the presence of Si-S double chains linked by some Si-Si covalent bonds together with a remarkable spd hybridization on Si. The increased stability is related to silicon forming four bonds, including an additional double-bond-like Si-Si bond. The involvement of d orbitals brings more variety to silicon-sulfide-based nanostructures that are isoelectronic to phosphorene, which could be relevant for future applications, adding extra degrees of freedom. ; This work has been partially supported by the Projects No. FIS2013-48286-C2-1-P and No. FIS2016-76617-P of the Spanish Ministry of Economy and Competitiveness MINECO, the Basque Government under the ETORTEK Program 2014 (nanoGUNE2014), and the University of the Basque Country (Grant No. IT-366-07). T.A.-L. acknowledges the grant of the MPC Material Physics Center - San Sebastian. F.A.-G. acknowledges the DIPC for their generous hospitality. We also want to acknowledge the DIPC computer center (T.A.L., A.A., and F.A.-G.). ; Peer reviewed

arXiv:1606.00165v1 ; We describe the structural and electronic properties of graphene doped with substitutional impurities of 4d and 5d transition metals. The adsorption energies and distances for 4d and 5d metals in graphene show similar trends for the later groups in the periodic table, which are also well-known characteristics of 3d elements. However, along earlier groups the 4d impurities in graphene show very similar adsorption energies, distances and magnetic moments to the 5d ones, which can be related to the influence of the 4d and 5d lanthanide contraction. Surprisingly, within the manganese group, the total magnetic moment of 3 μB for manganese is reduced to 1 μB for technetium and rhenium. We find that compared with 3d elements, the larger size of the 4d and 5d elements causes a high degree of hybridization with the neighbouring carbon atoms, reducing spin splitting in the d levels. It seems that the magnetic adjustment of graphene could be significantly different if 4d or 5d impurities are used instead of 3d impurities. ; This work has been partially supported by Project FIS2013-48286-C2-1-P of the Spanish Ministry of Economy and Competitiveness MINECO, by the Basque Government under the ETORTEK Program 2014 (nanoGUNE2014), and the University of the Basque Country (Grant No. IT-366-07). TAL acknowledge a grant provided by the MPC Materials Physics Center – San Sebastián. FA-G would like to thank the DIPC for their generous hospitality. We also acknowledge the assistance provided by the DIPC computer center (TAL, AA and FA-G). ; Peer reviewed

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. ; Grain boundaries and defect lines in graphene are intensively studied for their novel electronic and magnetic properties. However, there is not a complete comprehension of the appearance of localized states along these defects. Graphene grain boundaries are herein seen as the outcome of matching two semi-infinite graphene sheets with different edges. We classify the energy spectra of grain boundaries into three different types, directly related to the combination of the four basic classes of spectra of graphene edges. From the specific geometry of the grains, we are able to obtain the band structure and the number of localized states close to the Fermi energy. This provides a new understanding of states localized at grain boundaries, showing that they are derived from the edge states of graphene. Such knowledge is crucial for the ultimate tailoring of electronic and optoelectronic applications. ; This work was supported by the Polish National Science Center (grant DEC-2011/03/B/ST3/00091), the Basque Government through the NANOMATERIALS project (grant IE05-151) under the ETORTEK Program (iNanogune), the Spanish Ministerio de Ciencia y Tecnología (grants FIS2010-21282-C02-02, FIS2012-33521 and MONACEM projects), and the University of the Basque Country (grant no. IT-366-07). ; Peer Reviewed

Trabajo presentado al 42th "Jaszowiec" International School and Conference on the Physics of Semiconductors (Wisla-Polonia 2013). ; We study graphene nanoribbons and carbon nanotubes with divacancies, i.e., local defects composed of one octagon and a pair of pentagons. We show that the presence of divacancies leads to the appearance of gap states, which may act as acceptor or donor states. We explain the origin of those defect-localized states and prove that they are directly related to the zero-energy states of carbon ring forming the octagonal topological defect. ; This work was supported by the Polish National Science Center (grant DEC-2011/03/B/ST3/00091), the Spanish Ministry of Economy and Competitiveness (grant No. FIS2012-33521), the Basque Departamento de Educación and the University of the Basque Country (grant No. IT-366-07), the Basque Departamento de Industria and the Diputación Foral de Guipuzcoa under the ETORTEK program (NANO-IKER grant No. IE11-304). ; Peer Reviewed

10 páginas, 11 figuras.-- PACS number(s): 71.55.Eq, 75.75.Lf, 71.70.Gm ; We investigate the electronic and magnetic properties of (Ga,Mn)N nanocrystals using the density functional theory. We study both wurtzite and zinc-blende structures doped with one or two substitutional Mn impurities. For a single Mn dopant placed close to surface, the behavior of the empty Mn-induced state, hereafter referred to as "Mn hole," is different from bulk (Ga,Mn)N. The energy level corresponding to this off-center Mn hole lies within the quantum-dot gap near the conduction edge. For two Mn dopants, the most stable magnetic configuration is antiferromagnetic and this result was unexpected since (Ga,Mn)N bulk shows ferromagnetism in the ground state. The surprising antiferromagnetic alignment of two Mn spins is ascribed also to the holes linked to the Mn impurities that approach the surface. Unlike (Ga,Mn)N bulk, these Mn holes in confined (Ga,Mn)N nanostructures do not contribute to the ferromagnetic alignment of the two Mn spins. ; This work was supported by the Basque Government through the NANOMATERIALS project (Grant No. IE05-151) under the ETORTEK Program (iNanogune), the Spanish Ministerio de Ciencia y Tecnología of Spain (Grants No. TEC2007-68065-C03-03 and No. Fis2007- 66711-C02-02, and MONACEM project), and the University of the Basque Country (Grant No. IT-366-07). ; Peer reviewed

We investigate the electronic and magnetic properties of Mn-doped CdTe nanocrystals (NCs) with ∼2nm in diameter which can be experimentally synthesized with Mn atoms inside. Using the density-functional theory, we consider two doping cases: NCs containing one or two Mn impurities. Although the Mn d peaks carry five up electrons in the dot, the local magnetic moment on the Mn site is 4.65μB. It is smaller than 5μB because of the sp−d hybridization between the localized 3d electrons of the Mn atoms and the s- and p-type valence states of the host compound. The sp−d hybridization induces small magnetic moments on the Mn-nearest-neighbor Te sites, antiparallel to the Mn moment affecting the p-type valence states of the undoped dot, as usual for a kinetic-mediated exchange magnetic coupling. Furthermore, we calculate the parameters standing for the sp−d exchange interactions. Conduction N0α and valence N0β are close to the experimental bulk values when the Mn impurities occupy bulklike NCs' central positions, and they tend to zero close to the surface. This behavior is further explained by an analysis of valence-band-edge states showing that symmetry breaking splits the states and in consequence reduces the exchange. For two Mn atoms in several positions, the valence edge states show a further departure from an interpretation based in a perturbative treatment. We also calculate the d−d exchange interactions ∣∣Jdd∣∣ between Mn spins. The largest ∣∣Jdd∣∣ value is also for Mn atoms on bulklike central sites; in comparison with the experimental d−d exchange constant in bulk Cd0.95Mn0.05Te, it is four times smaller. ; This work was supported by the Basque Government through the NANOMATERIALS project Project No. IE05-151 under the ETORTEK Program NANOMAT, Spanish Ministerio de Ciencia y Tecnología MCyT of Spain Grant No. Fis 2004-06490-CO3-00 and MONACEM project, and the European Network of Excellence NANOQUANTA Grant No. NM4-CT-2004-500198. ; Peer reviewed

We investigate the optical properties of (Cd,Mn)Te quantum dots (QDs) by looking at the excitons as a function of the Mn impurities positions and their magnetic alignments. When doped with two Mn impurities, the Mn spins, aligned initially antiparallel in the ground state, have lower energy in the parallel configuration for the optically active spin-up exciton. Hence, the photoexcitation of the QD ground state with antiparallel Mn spins induces one of them to flip and they align parallel. This suggests that (Cd,Mn)Te QDs are suitable for spin-based operations handled by light. ; This work was supported by the Basque Government through the NANOMATERIALS Project (Grant No. IE05-151) under the ETORTEK Program (iNanogune), Spanish Ministerio de Ciencia y Tecnología (MCyT) of Spain (Grant Nos. TEC2007-68065-C03-03 and Fis2007-66711-CO2-02, and MONACEM project), and University of the Basque Country (Grant No. IT-366-07). The computing resources from the Donostia International Physics Center (DIPC) and the SGI-SGIkerUPV are gratefully acknowledged. ; Peer reviewed

arXiv:1506.00869v1 ; We report the electronic properties of two-dimensional systems made of graphene nanoribbons, which are patterned with ad-atoms in two separated regions. Due to the extra electronic confinement induced by the presence of impurities, we find resonant levels, quasi-bound and impurity-induced localized states, which determine the transport properties of the system. Regardless of the ad-atom distribution in the system, we apply band-folding procedures to simple models and predict the energies and the spatial distribution of those impurity-induced states. We take into account two different scenarios: gapped graphene and the presence of randomly distributed ad-atoms in a low dilution regime. In both cases the defect-induced resonances are still detected. Our findings would encourage experimentalists to synthesize these systems and characterize their quasi-localized states by employing, for instance, scanning tunneling spectroscopy (STS). Additionally, the resonant transport features could be used in electronic applications and molecular sensing devices. ; This work has been partially supported by the Project FIS2013-48286-C2-1-P of the Spanish Ministry of Economy and Competitiveness MINECO (JWG, AA), the Basque Government through the NANOMATERIALS project (Grant IE14-393) under the ETORTEK Program Nanogune14 (JWG, AA) and the University of the Basque Country (Grant No. IT-366-07) (JWG, AA). Chilean FONDECYT grants: 1140388 (LR), and 1151316 (MP), and DGIP/USM internal grant 11.14.68 (MP), CONICYT ACT 1204 (LR, MP). ; Peer Reviewed

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. ; The presence of giant diamagnetism in Au nanorods, NRs, is shown to be a possible consequence of field induced currents in the surface electrons. The distance, Δ, between quantum surface energy levels has been calculated as a function of the NRs radius. Note that those electrons occupying states for which Δ>kB T are steadily orbiting with constant orbital moment. The diamagnetic response induced when a field is turned on remains constant during the time the field is acting. As the NRs radius increases, Δ decreases and accordingly the electron fraction available to generate constant currents decreases, consequently the surface diamagnetic susceptibility decreases towards its bulk value. The surface electronic motion induced by the axial applied field on electrons confined into a cylindrical surface accounts with extremely good quantitative agreement for the giant diamagnetism recently measured and reported. © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. ; We gratefully acknowledge financial support from the Spanish Ministerio de Innovación, Ciencia y Tecnología (grant numbers MAT2012-37109-C02-01 and FIS2010-21282-C02-02), the University of the Basque Country (grant no. IT-366-07), the Basque Government through the NANOMATERIALS project (grant IE05-151) under the ETORTEK Program (iNanogune). ; Peer Reviewed

3 pages, 1 figure.-- PACS nrs.: 73.21.La, 73.22.-f, 73.20.At, 71.15.Ap.-- Presented as poster communication to TNT 2008: Trends in NanoTechnology (Oviedo, Spain, Sep 1-5, 2008). ; The interface states of all-metallic carbon nanotube quantum dots are studied based on a tight-binding approach and a Green's function matching technique. We have found that depending on the type of metallic tube, the energy of interface states may show an oscillatory behavior. We identify these as steamming from Friedel oscillations. We comment on the possible implications of this finding on other physical properties, such as stability during the growth of nanotube junctions and magnetic interaction through carbon nanotubes. ; We acknowledge financial support by the ETORTEK (NANOMAT) program of the Basque government, the Intramural Special Project (Ref. No. 2006601242), the Spanish Ministerio de Ciencia y Tecnología (Grants No. Fis 2007-66711-C02-C01 and MAT2006-06242) and the European Network of Excellence NANOQUANTA (NM4-CT-2004-500198). ; Peer reviewed

Proceedings of the XXXVII International School of Semiconducting Compounds, Jaszowiec 2008. ; Interface states of all-metallic carbon nanotube quantum dots and superlattices are studied within a tight-binding model. We focus on achiral systems made by connecting armchair (n; n) and zigzag (2n; 0) tubes with a full ring of n pentagon-heptagon topological defects. We show that the coupling between interface states, which arise from the topological defects, re°ects the existence of the Friedel oscillations in the (n; n) tube, with an unusually large decay exponent. We expect this interaction to be important for the understanding of other physical properties, such as selective dot growth, magnetic interaction through carbon tubes or optical spectroscopy of interface states. ; We acknowledge financial support by the ETORTEK (NANOMAT) program of the Basque government, the Intramural Special Project (Ref. 2006601242), the Spanish Ministerio de Ciencia y Tecnologia (Grants No. Fis 2007-66711-C02-C01 and MAT2006-06242), JCCM Grant No. PAI08-0067-2673 and the European Network of Excellence NANOQUANTA (NM4-CT-2004-500198). ; Peer reviewed