Conductance anisotropy and linear magnetoresistance in La2-xSrxCuO4 thin films

We have performed a detailed study of conductance anisotropy and magnetoresistance (MR) of La2-xSrxCuO4 (LSCO) thin films (0.10 < x < 0.25). These two observables are promising for the detection of stripes. Subtle features of the conductance anisotropy are revealed by measuring the transverse resistance Rxy in zero magnetic field. It is demonstrated that the sign of Rxy depends on the orientation of the LSCO Hall bar with respect to the terrace structure of the substrate. Unit-cell-high substrate step edges must therefore be a dominant nucleation source for antiphase boundaries during film growth. We show that the measurement of Rxy is sensitive enough to detect the cubic-tetragonal phase transition of the SrTiO3(100) (STO) substrate at 105 K. The MR of LSCO thin films shows for 0.10 < x < 0.25 a non-monotonic temperature dependence, resulting from the onset of a linear term in the MR above 90 K. We show that the linear MR scales with the absolute Hall resistivity, with the constant of proportionality independent of temperature. Such scaling suggests that the linear MR originates from current distortions induced by structural or electronic inhomogeneities. The possible role of stripes for both the MR and the conductance anisotropy is discussed throughout the paper

Proximity effect in normal metal-multiband superconductor hybrid structures

A theory of the proximity effect in normal metal¿multiband superconductor hybrid structures is formulated within the quasiclassical Green's function formalism. The quasiclassical boundary conditions for multiband hybrid structures are derived in the dirty limit. It is shown that the existence of multiple superconducting bands manifests itself as the occurrence of additional peaks in the density of states in the structure. The interplay between the proximity effect and the interband coupling influences the magnitudes of the gaps in a superconductor in a nontrivial way and can even give rise to an enhancement of multiband superconductivity by the proximity to a superconductor with a lower transition temperature. The developed theory is applied to the calculation of supercurrent in multiband superconductor¿normal metal¿superconductor Josephson junctions with low-transparent interfaces, and the results are compared with the predictions for multiband tunnel junctions

Observability of surface Andreev bound states in a topological insulator in proximity to an s-wave superconductor

To guide experimental work on the search for Majorana zero-energy modes, we calculate the superconducting pairing symmetry of a three-dimensional topological insulator in combination with an s-wave superconductor. In analogy to the case of nanowires with strong spin-orbit coupling we show how the pairing symmetry changes across different topological regimes. We demonstrate that a dominant p-wave pairing relation is not sufficient to realize a Majorana zero-energy mode useful for quantum computation. Our main result of this paper is the relation between odd-frequency pairing and Majorana zero energy modes by using Green functions techniques in three-dimensional topological insulators in the so-called Majorana regime. We discuss thereafter how the pairing relations in the different regimes can be observed in the shape of the tunneling conductance of an s-wave proximized three-dimensional topological insulator. We will discuss the necessity to incorporate a ferromagnetic insulator to localize the zero-energy bound state to the interface as a Majorana mode.Comment: Accepted for publication in Journal of Physics: Condensed Matte

Nonlocal Andreev reflection, fractional charge and current-phase relation in topological bilayer exciton condensate junctions

We study Andreev reflection and Josephson currents in topological bilayer exciton condensates (TEC). These systems can create 100% spin entangled nonlocal currents with high amplitudes due to perfect nonlocal Andreev reflection. This Andreev reflection process can be gate tuned from a regime of purely retro reflection to purely specular reflection. We have studied the bound states in TEC-TI-TEC Josephson junctions and find a gapless dispersion for perpendicular incidence. The presence of a sharp transition in the supercurrent-phase relationship when the system is in equilibrium is a signature of fractional charge, which can be further revealed in ac measurements faster than relaxation processes via Landau-Zener processes.Comment: Submitted to Physical Review

VPI Processes and Resin Evaluations for CPA Electrical Windings

High energy density requirements for fieldable electric gun applications has led to the air-core compensated pulsed alternator (CPA) or compulsator as the generator of choice to provide pulse power. The air-core nature of the machines combined with ambitious power density requirements has led to the minimizing of metallic supporting structures which places additional structural requirements on the electrical windings within the generators.Center for Electromechanic

Sex, Culture, and the Politics of Fashion in Stuart England

This dissertation is the first full-length study to analyze the politicization of dress and material objects, exploring the manner in which fashion served as a site for political discourse and agency, during the seventeenth century, specifically from 1603–1702, an era characterized by profound political, religious, and social turmoil as well as increased international trade and luxury consumption. This dissertation demonstrates how fashion, which encompassed clothing, accessories, hairstyling, and cosmetics, was an important facet of political culture within Stuart England and, furthermore, was absolutely fundamental to how the English understood themselves, others, and the turbulent world they lived in. I argue that dress often figured, in both a rhetorical and material sense, at the center of political debates during the Stuart period, particularly in regards to issues of foreign influence, the threat of Catholicism, regicide, the problem of succession, “party” politics, and conceptions of “Englishness.” This study analyzes a variety of primary sources including cheap printed works, royal household records, state papers, personal correspondence and diaries, as well as extant objects and court portraiture, in order to reveal how political and material culture were deeply entwined. While current histories of early modern dress emphasize the continuities of fashion during this period, this dissertation offers a reinterpretation of this traditional perspective but demonstrating how, while some styles and garments certainly changed over time, the particular political attitudes associated with such garb, such as anti-French and anti-Catholic sentiment, remained constant threads within the rich tapestry of Stuart politics. Furthermore, this dissertation contributes to not simply the cultural and political history of Stuart England, but also important scholarship on the political agency of early modern women, seventeenth-century notions of “whiteness” and “blackness,” the development of Britain’s trade empire, and the concept of an English national identity