Spin accumulation encoded in electronic noise for mesoscopic billiards with finite tunneling rates

Ramos, J. Galvão; Barbosa, A. L. R.; Bazeia, D.; Hussein, M. S.

doi:10.1103/physrevb.85.115123

Cited by 8 publications

(2 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For nickelates, x-ray absorption spectra [16,17] reveal that local signatures of Ni1 and Ni2 sites persist continuously across the MIT, and both sites also remain when driven across the phase boundary by pressure. [37] As we have shown, the coordination alone (i.e. with identical n d ) accounts for on-site energy differences of ∼1 eV in spectra that have often been used to support disproportionation.…”

mentioning

confidence: 74%

Formal Valence,3d-Electron Occupation, and Charge-Order Transitions

2012

View full text Add to dashboard Cite

While the formal valence and charge state concepts have been tremendously important in materials physics and chemistry, their very loose connection to actual charge leads to uncertainties in modeling behavior and interpreting data. We point out, taking several transition metal oxides (La2VCuO6, YNiO3, CaFeO3, AgNiO2, V4O7) as examples, that while dividing the crystal charge into atomic contributions is an ill-posed activity, the 3d occupation of a cation (and more particularly, differences) is readily available in first principles calculations. We discuss these examples, which include distinct charge states and charge-order (or disproportionation) systems, where different "charge states" of cations have identical 3d orbital occupation. Implications for theoretical modeling of such charge states and charge-ordering mechanisms are discussed.Spin ordering, and often orbital ordering, is normally unambiguous, as these properties are subject to direct observation by magnetic and spectroscopic measurements, respectively. Charge ordering (CO) and the actual charge of an ion is rarely measured directly, and the formal charge of an ion in the solid state can be a point of confusion and contention. Valence, oxidation number, and formal charge are concepts borrowed from chemistry, where it is emphasized they do not represent actual charge [1,2] and have even been labeled hypothetical.[1] As the interplay between spin, charge, orbital, and lattice degrees of freedom become more closely watched [3] and acknowledged to be a complex phenomenon, disproportionation and CO have become entrenched as the explanation of several high profile metalinsulator transitions (MIT). The possibility that CO in the charge transfer regime is associated with the oxygen sublattice, with negligible participation of the metal, has been raised[4] and considered as an alternative. [5] Charge density is a physical observable of condensed matter, and the desire to assign charge to atoms has evident pedagogical value, so theoretical approaches have been devised to share it amongst constituent nuclei. Mulliken charge population, which socializes shared charge (divides it evenly between overlapping orbitals) is notoriously sensitive to the local orbital basis set that is required to specify it. Born effective charges are dynamical properties and are often quite different from any conceivable formal charge or actual charge. Integrations over various volumes have been used a great deal, but dividing the static crystal charge density into atomic contributions is, undeniably, an ill-defined activity.A possibility that has not been utilized is that, taking 3d oxides as an example, there is a directly relevant metric that is well defined: the d occupation n d . This quantity is in fact what the physical picture of formal charge or oxidation state brings to mind. 3d cations, in their various environments and charge states, have maxima in their spherically averaged radial densityρ(r) in the range 0.6-0.9 a o . At this short distance from the nucleus, the only oth...

show abstract

mentioning

confidence: 74%

Formal Valence,3d-Electron Occupation, and Charge-Order Transitions

2012

View full text Add to dashboard Cite

show abstract

“…The USCFs appear in the transverse current measured in multiterminal devices in the presence of a sufficiently large magnetic field. 6 Signals of the spin accumulation can be inferred, for instance, from time-dependent fluctuations of the spectral currents (noise power) 10 or from the analysis of universal conductance fluctuations. [11][12][13][14] Spin Hall conductance fluctuations have been theoretically studied for mesoscopic systems in the diffusive 11 as well as in the ballistic regime.…”

Section: Introductionmentioning

confidence: 99%

Generalized correlation functions for conductance fluctuations and the mesoscopic spin Hall effect

et al. 2012

Self Cite

View full text Add to dashboard Cite

We study the spin Hall conductance fluctuations in ballistic mesoscopic systems. We obtain universal expressions for the spin and charge current fluctuations, cast in terms of current-current autocorrelation functions. We show that the latter are conveniently parametrized as deformed Lorentzian shape lines, functions of an external applied magnetic field and the Fermi energy. We find that the charge current fluctuations show quite unique statistical features at the symplectic-unitary crossover regime. Our findings are based on an evaluation of the generalized transmission coefficients correlation functions within the stub model and are amenable to experimental test.

show abstract