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Nuevas investigaciones sobre el arte paleolítico de la cueva de Arenaza (Galdames, Bizkaia)
Diego Garate
Munibe Antropologia-Arkeologia , 2004,
Abstract: El hallazgo de nuevas evidencias gráficas en la cueva de Arenaza (Galdames, Bizkaia), concretamente un antropomorfo grabado y un signo rectangular rojo, aporta una aproximación más compleja y precisa al conjunto parietal paleolítico. Se trata de dos temas inéditos en dicha cueva cuya comparación con grafías similares en la región cantábrica permite matizar la adscripción cronólogica del conjunto.
Charge-Kondo Effect in Mesoscopic Superconductors Coupled to Normal Metals
Ion Garate
Physics , 2011, DOI: 10.1103/PhysRevB.84.085121
Abstract: We develop a theoretical proposal for the charge Kondo effect in mesoscopic normal-superconductor-normal heterostructures, where the superconducting gap exceeds the electrostatic charging energy. Charge-Kondo correlations in these devices alter the conventional temperature-dependence of Andreev reflection and electron cotunneling. We predict typical Kondo temperatures of $\gtrsim 10 {\rm mK}$, and suggest experimental architectures that combine superconducting charge-qubits with semiconducting nanowires at cryogenic temperatures.
Phonon-induced topological transitions and crossovers in Dirac materials
Ion Garate
Physics , 2012, DOI: 10.1103/PhysRevLett.110.046402
Abstract: We show that electron-phonon interactions can alter the topological properties of Dirac insulators and semimetals, both at zero and nonzero temperature. Contrary to the common belief that increasing temperature always destabilizes topological phases, our results highlight instances in which phonons may lead to the appearance of topological surface states above a crossover temperature in a material that has a topologically trivial ground state.
Possible charge analogues of spin transfer torques in bulk superconductors
Ion Garate
Physics , 2013, DOI: 10.1103/PhysRevB.88.094511
Abstract: Spin transfer torques (STT) occur when electric currents travel through inhomogeneously magnetized systems and are important for the motion of magnetic textures such as domain walls. Since superconductors are easy-plane ferromagnets in particle-hole (charge) space, it is natural to ask whether any charge duals of STT phenomena exist therein. We find that the superconducting analogue of the adiabatic STT vanishes in a bulk superconductor with a momentum-independent order parameter, while the superconducting counterpart of the nonadiabatic STT does not vanish. This nonvanishing superconducting torque is induced by heat (rather than charge) currents and acts on the charge (rather than spin) degree of freedom. It can become significant in the vicinity of the superconducting transition temperature, where it generates a net quasiparticle charge and alters the dispersion and linewidth of low-frequency collective modes.
Bioincrustantes en estructuras de cultivo de Argopecten purpuratus en Bahía Samanco, Perú
Aldo Pacheco,Antonio Garate
Ecología Aplicada , 2005,
Abstract: Los bioincrustantes, son organismos que se adhieren sobre estructuras duras que se sumergen o están en contacto continuo con el agua de mar. Con el objetivo de dar a conocer la composición de especies bioincrustantes en el cultivo suspendido de Argopecten purpuratus, el día 20 de Octubre de 1998 se realizó un muestreo de diferentes materiales y sobre las valvas de las conchas, en la Concesión de Maricultura de la Universidad Ricardo Palma (Bahía Samanco, Ancash, Perú). Se identificaron un total de 33 especies pertenecientes a 10 grupos taxonómicos. Las diferentes especies correspondieron a ambientes, intermareales, submareales y pelágicos.
El proceso gráfico de la pintura punteada cantábrica : hacia la identificación de uina cadena operativa artística
Garate Maidagan, Diego
Munibe Antropologia-Arkeologia , 2007,
Abstract: La aproximación a la actividad artística en la investigación del arte parietal paleolitico plantea diversas posibilidades. En los últimos a os, y sobre todo en lo que se refiere al arte mobiliar, se ha progresado en la recoonstitución de la cadena operativa gráfica. En este caso, nos cetramos en las pinturas punteadas cantábricas para las que se reconoce una homogeneidad estilística excepcional durante un periodo cronológico amplio (Gravetiense-Solutrense). Asimismo, presentan una pautas comunes en lo que se refiere al proceso artístico (abastecimiento de materia prima, transformación en materia colorante, elección del medio de aplicación, procedimiento jerarquizado de aplicación, etc.) que serán precisadas.
Inverse Spin-Galvanic Effect in a Topological-Insulator/Ferromagnet Interface
Ion Garate,M. Franz
Physics , 2009, DOI: 10.1103/PhysRevLett.104.146802
Abstract: When a ferromagnet is deposited on the surface of a topological insulator the topologically protected surface state develops a gap and becomes a 2-dimensional quantum Hall liquid. We demonstrate that the Hall current in such a liquid, induced by an external electric field, can have a large effect on the magnetization dynamics of the ferromagnet by changing the effective anisotropy field. This change is dissipationless and may be substantial even in weakly spin-orbit coupled ferromagnets. We study the possibility of dissipationless current-induced magnetization reversal in monolayer-thin, insulating ferromagnets with a soft perpendicular anisotropy and discuss possible applications of this effect.
Magnetoelectric Response of the Time-Reversal Invariant Helical Metal
Ion Garate,M. Franz
Physics , 2010, DOI: 10.1103/PhysRevB.81.172408
Abstract: We derive compact analytical expressions for the coupled spin-charge susceptibility of a clean helical metal at the surface of a three dimensional topological insulator (TI). These expressions lead to unconventional non-collinear RKKY interactions between two impurity magnetic moments placed on the surface of a TI, and predict the generation of electric currents by time-dependent magnetic moments. We determine the influence of gate and bias voltages on the interlayer exchange coupling between two single-domain ferromagnetic monolayers deposited on top of a TI.
Interplay between Symmetric Exchange Anisotropy, Uniform Dzyaloshinskii-Moriya Interaction and Magnetic Fields in the Phase Diagram of Quantum Magnets and Superconductors
Ion Garate,Ian Affleck
Physics , 2010, DOI: 10.1103/PhysRevB.81.144419
Abstract: We theoretically study the joint influence of uniform Dzyaloshinskii-Moriya (DM) interactions, symmetric exchange anisotropy (with its axis parallel to the DM vector) and arbitrarily oriented magnetic fields on one-dimensional spin 1/2 antiferromagnets. We show that the zero-temperature phase diagram contains three competing phases: (i) an antiferromagnet with Neel vector in the plane spanned by the DM vector and the magnetic field, (ii) a {\em dimerized} antiferromagnet with Neel vector perpendicular to both the DM vector and the magnetic field, and (iii) a gapless Luttinger liquid. Phase (i) is destroyed by a small magnetic field component along the DM vector and is furthermore unstable beyond a critical value of easy-plane anisotropy, which we estimate using Abelian and non-Abelian bosonization along with perturbative renormalization group. We propose a mathematical equivalent of the spin model in a one-dimensional Josephson junction (JJ) array located in proximity to a bulk superconductor. We discuss the analogues of the magnetic phases in the superconducting context and comment on their experimental viability.
Gilbert Damping in Conducting Ferromagnets II: Model Tests of the Torque-Correlation Formula
Ion Garate,Allan MacDonald
Physics , 2008, DOI: 10.1103/PhysRevB.79.064404
Abstract: We report on a study of Gilbert damping due to particle-hole pair excitations in conducting ferromagnets. We focus on a toy two-band model and on a four-band spherical model which provides an approximate description of ferromagnetic (Ga,Mn)As. These models are sufficiently simple that disorder-ladder-sum vertex corrections to the long-wavelength spin-spin response function can be summed to all orders. An important objective of this study is to assess the reliability of practical approximate expressions which can be combined with electronic structure calculations to estimate Gilbert damping in more complex systems.
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