Horacio E. Camblong

Quantum Anomaly in Molecular Physics

The interaction of an electron with a polar molecule is shown to be the simplest realization of a quantum anomaly in a physical system. The existence of a critical dipole moment for electron capture and formation of anions, which has been confirmed experimentally and numerically, is derived. This phenomenon is a manifestation of the anomaly associated with quantum symmetry breaking of the classical scale invariance exhibited by the point-dipole interaction. Finally, analysis of symmetry breaking for this system is implemented within two different models: point dipole subject to an anomaly and finite dipole subject to explicit symmetry breaking.

Renormalization of the inverse square potential

The quantum-mechanical D-dimensional inverse square potential is analyzed using field-theoretic renormalization techniques. A solution is presented for both the bound-state and scattering sectors of the theory using cutoff and dimensional regularization. In the renormalized version of the theory, there is a strong-coupling regime where quantum-mechanical breaking of scale symmetry takes place through dimensional transmutation, with the creation of a single bound state and of an energy-dependent s-wave scattering matrix element.

Theory of magnetotransport in inhomogeneous magnetic structures

The origin of the giant magnetoresistance of magnetic multilayers and magnetic granular solids is investigated through a unified spin‐dependent linear transport theory, in which the primary source of electrical resistivity is short‐range scattering by impurities in the different magnetic or nonmagnetic regions and at the interfaces. Our theory predicts that magnetotransport in granular solids is similar to that for currents perpendicular to the plane of the layers in multilayers in that their magnetoresistance is independent of the average distance between adjacent magnetic regions.

Interlayer coupling and magnetoresistance of multilayered structures

Abstract The spin polarization of conduction electrons in paramagnetic layers due to adjacent magnetic layers has been recently observed for copper spacer layers, and in a chromium wedge-like film on top of an iron whisker. Also, we explain the relation of this spin polarization to the indirect coupling of the magnetic layers through paramagnetic spacer layers. We show that the effect of spin-dependent potentials in magnetic multilayers is far more pronounced for CPP-MR than for CIP-MR. This can add to the difference between CIP-MR and CPP-MR that is due to the spin-dependent scattering in the multilayers.

Magnetic multilayers: Quasiclassical transport via the Kubo formula

A real‐space quantum approach, based on the Kubo formula, is used to describe the quasiclassical transport behavior of metallic multilayers. We emphasize the differences between the cases of current in the plane of the layers, for which size effects play a dominant role and current perpendicular to the planes, for which we provide several proofs that the so‐called series resistor model holds for all length scales.

Effective internal fields and magnetization buildup for magnetotransport in magnetic multilayered structures

Starting with the Kubo formula for electric conductivity we derive a set of equations that define the spin diffusion that is present when current is driven through inhomogeneous magnetic media. We show the spin accumulation, or nonequilibrium magnetization, attendant to charge transport through regions of inhomogeneous magnetization is governed by the same equations found in a thermodynamic approach to magnetoelectric transport.

Electrical Resistivity of a Thin Metallic Film

The electrical resistivity of a pure sample of a thin metallic film is found to depend on the boundary conditions. This conclusion is supported by a free-electron model calculation and confirmed by an ab initio relativistic Korringa-Kohn-Rostoker computation. The low-temperature resistivity is found to be zero for a free-standing film (reflecting boundary conditions) but nonzero when the film is sandwiched between two semi-infinite samples of the same material (outgoing boundary conditions). In the latter case, this resistivity scales inversely with the number of monolayers and is due to the background diffusive scattering by a finite lattice.

Theory of conductance and magnetoresistance of magnetic multilayered structures

Abstract We use a real space quantum approach, based on the Kubo formula and a model Hamiltonian with spin-dependent zero-range potentials, to describe the transport properties of metallic multilayers. Our general solution is remarkably simple and corrects the usual quasiclassical treatment of interfaces.

The Influence of Magnetism and Structure on Transport Properties and Interlayer Coupling of Systems in Reduced Dimensions

Recent attention has been focused on magnetic multilayered structures and thin films containing magnetic granules which display a new magnetoresistive (MR) effect. This effect, first found in Fe/Cr multilayered structures, has now been observed in at least a dozen different combinations of magnetic and non-magnetic metallic layers. In addition, two groups have recently observed the effect for thin films containing magnetic particles, e.g., copper with cobalt precipitates.

The influence of potential barriers on magnetoresistance of magnetic multilayers (abstract)

There is an emerging interest in the CPP (current perpendicular to the plane of layers) geometry for transport measurements1 and we report on new developments on the CPP‐MR (magnetoresistance). Specifically we show that the effect of spin‐dependent potentials in magnetic multilayers is far more pronounced for CPP‐MR than for CIP‐MR (current in the plane of layers). This adds to the difference between CIP‐MR and CPP‐MR that is due to the spin‐dependent scattering in the multilayers.2 The potentials seen by the spin up and the spin down conduction electrons are different, and they depend on the orientation of the magnetic layers relative to one another, i.e., they are different for ferro and antiferromagnetically aligned layers. We have determined the Bloch functions appropriate to these spin‐dependent potentials,3 and have used the Kubo formalism to calculate the resistivity and magnetoresistance for both CIP and CPP geometries. In general these potentials do affect the CIP‐MR; however, for uniform scatter...