Large enhancement of the thermoelectric power factor in disordered materials through resonant scattering

In the search for more efficient thermoelectric materials, scientists have placed high hopes in the possibility of enhancing the power factor using resonant states. In this study, we investigate theoretically the effects of randomly distributed resonant impurities on the power factor. Using the Chebyshev Polynomial Green's Function method, we compute the electron transport properties for very large systems (10 million atoms) with an exact treatment of disorder. The introduction of resonant defects can lead to a large enhancement of the power factor together with a sign inversion in the Seebeck coefficient. This boost depends crucially on the position of the resonant peak, and on the interplay between elastic impurity scattering and inelastic processes. Strong electron-phonon or electron-electron scattering are found detrimental. Finally, the robustness of our results is examined in the case of anisotropic orbitals and two-dimensional confinement. Our findings are promising for the prospect of thermoelectric power generation.Comment: To appear in Phys. Rev.

Género e historia en Francia: los usos de un término y de una categoría de análisis

What does gender history mean? After investigating the recent emergency of this term in History as well as in Human Sciences in France, this article explains spaces. It describes seven possible uses of the analysis category, and proposes, of course, through an historiographic thought, an scope of recent investigation in this country, concerning women history and gender history.¿Qué es la historia del género? Después de examinar la reciente emergencia del término en Historia y Ciencias Humanas en Francia, este artículo explicita los ámbitos. Describe siete usos posibles de esta categoría de análisis y propone, por tanto, a través de una reflexión historiográfica, un panorama de la investigación actual en este país relativa a la historia de las mujeres y del género

In countries with little work-family support, many women opt for self-employment

But they typically employ few workers and join less innovative industries, writes Sarah Thébau

Absence of confinement in (SrTiO3)/(SrTi0:8Nb0:2O3) superlattices

The reduction of dimensionality is an efficient pathway to boost the performances of thermoelectric materials, it leads to the quantum confinement of the carriers and thus to large Seebeck coefficients (S) and it also suppresses the thermal conductivity by increasing the phonon scattering processes. However, quantum confinement in superlattices is not always easy to achieve and needs to be carefully validated. In the past decade, large values of S have been measured in (SrTiO3)/(SrTi0:8Nb0:2O3) superlattices (Nat. Mater. 6, 129 (2007) and Appl. Phys. Lett. 91, 192105 (2007)). In the $\delta$-doped compound, the measured S was almost 6 times larger than that of the bulk material. This huge increase has been attributed to the two dimensional confinement of the carriers in the doped regions. In this work, we demonstrate that the experimental data can be well explained quantitatively within the scenario in which electrons are delocalized in both in-plane and growth directions, hence strongly suggesting that the confinement picture in these superlattices may be unlikely.Comment: 5 figures, manuscript submitte

MSCS in Scenarios of Infection and Inflammation: Focus on Neonatal Diseases

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