Julen Ibañez-Azpiroz

Relativistic effects and fully spin-polarized Fermi surface at the Tl/Si(111) surface

We present a detailed analysis of the relativistic electronic structure and the momentum dependent spin-polarization of the Tl/Si(111) surface. Our first principle calculations reveal the existence of fully spin-polarized electron pockets associated to the huge spin-splitting of metallic surface bands. The calculated spin-polarization shows a very complex structure in the reciprocal space, strongly departing from simple theoretical model approximations. Interestingly, the electronic spin-state close to the Fermi surface is polarized along the surface perpendicular direction and reverses its orientation between different electron pockets.

Self-consistent tight-binding description of Dirac points moving and merging in two dimensional optical lattices

This work has been supported by the UPV/EHU under programs UFI 11/55 and IT-366-07, the Spanish Ministry of Science and Innovation through Grants No. FIS2010-19609-C02-00 and No. FIS2012-36673-C03-03, and the Basque Government through Grant No. IT-472-10.

Tight-binding models for ultracold atoms in honeycomb optical lattices

This work has been supported by the UPV/EHU under programs UFI 11/55 and IT-366-07, the Spanish Ministry of Science and Innovation through Grant No. FIS2010-19609-C02-00, and the Basque Government through Grant No. IT-472-10.

A gateway towards non-collinear spin processing using three-atom magnets with strong substrate coupling

A cluster of a few magnetic atoms on the surface of a nonmagnetic substrate is one suitable realization of a bit for spin-based information technology. The prevalent approach to achieve magnetic stability is decoupling the cluster spin from substrate conduction electrons in order to suppress destabilizing spin-flips. However, this route entails less flexibility in tailoring the coupling between the bits needed for spin-processing. Here, we use a spin-resolved scanning tunneling microscope to write, read, and store spin information for hours in clusters of three atoms strongly coupled to a substrate featuring a cloud of non-collinearly polarized host atoms, a so-called non-collinear giant moment cluster. The giant moment cluster can be driven into a Kondo screened state by simply moving one of its atoms to a different site. Using the exceptional atomic tunability of the non-collinear substrate mediated Dzyaloshinskii–Moriya interaction, we propose a logical scheme for a four-state memory.Information technology based on few atom magnets requires both long spin-energy relaxation times and flexible inter-bit coupling. Here, the authors show routes to manipulate information in three-atom clusters strongly coupled to substrate electrons by exploiting Dzyaloshinskii–Moriya interactions.

Ab initio analysis of plasmon dispersion in sodium under pressure

The authors acknowledge financial support from UPV/EHU (Grant No. IT-366-07) and the Spanish Ministry of Science and Innovation (Grant No. FIS2010-19609-C02-00).

Breakdown of the Peierls substitution for the Haldane model with ultracold atoms

We present two independent approaches for calculating the tight-binding parameters of the Haldane model with ultracold atoms. The tunneling coefficients up to next-nearest neighbors are computed ab initio by using the maximally localized Wannier functions and compared to analytical expressions written in terms of gauge-invariant measurable properties of the spectrum. The two approaches present a remarkable agreement and evidence the breakdown of the Peierls substitution: (i) the phase acquired by the next-nearest tunneling amplitude t1 presents quantitative and qualitative differences with respect to that obtained by the integral of the vector field A ,a s considered in the Peierls substitution, even in the regime of low amplitudes of A; and (ii) for larger values, also |t1| and the nearest-neighbor tunneling t0 have a marked dependence on A. The origin of this behavior and its implications are discussed.

Ab initio analysis of the topological phase diagram of the Haldane model

We present an ab initio analysis of a continuous Hamiltonian that maps into the celebrated Haldane model. The tunnelling coecients of the tight-binding model are computed by means of two independent methods - one based on the maximally localised Wannier functions, the other through analytic expressions in terms of gauge-invariant properties of the spectrum - that provide a remarkable agreement and allow to accurately reproduce the exact spectrum of the continuous Hamiltonian. By combining these results with the numerical calculation of the Chern number, we are able to draw the phase diagram in terms of the physical parameters of the microscopic model. Remarkably, we nd that only a small fraction of the original phase diagram of the Haldane model can be accessed, and that the topological insulator phase is suppressed in the deep tight-binding regime. Moreover, we nd that in the case of parity breaking, the topological phase transition for the continuous Hamiltonian takes place without gap closing.

Ab initio investigation of impurity-induced in-gap states in Bi

We investigate in-gap states emerging when a single

_2

3d

Te

transition metal impurity is embedded in topological insulators (