3,349 research outputs found
Spin-Filtering Multiferroic-Semiconductor Heterojunctions
We report on the structural and electronic properties of the interface
between the multiferoic oxide YMnO and wide band-gap semiconductor GaN
studied with the Hubbard-corrected local spin density approximation (LSDA+U) to
density-functional theory (DFT). We find that the band offsets at the interface
between antiferromagnetically ordered YMnO and GaN are different for
spin-up and spin-down states. This behavior is due to the spin splitting of the
valence band induced by the interface. The energy barrier depends on the
relative orientation of the electric polarization with respect to the
polarization direction of the GaN substrate suggesting an opportunity to create
magnetic tunnel junctions in this materials system.Comment: 4 pages, 4 figure
Interfacial Magnetoelectric Coupling in Tri-component Superlattices
Using first-principles density functional theory, we investigate the
interfacial magnetoelectric coupling in a tri-component superlattice composed
of a ferromagnetic metal (FM), ferroelectric (FE), and normal metal (NM). Using
Fe/FE/Pt as a model system, we show that a net and cumulative interfacial
magnetization is induced in the FM metal near the FM/FE interface. A carefully
analysis of the magnetic moments in Fe reveals that the interfacial
magnetization is a consequence of a complex interplay of interfacial charge
transfer, chemical bonding, and spin dependent electrostatic screening. The
last effect is linear in the FE polarization, is switchable upon its reversal,
and yields a substantial interfacial magnetoelectric coupling.Comment: 5 pages, 6 figure
Magnetoelectric Coupling and Electric Control of Magnetization in Ferromagnet-Ferroelectric-Metal Superlattices
Ferromagnet-ferroelectric-metal superlattices are proposed to realize the
large room-temperature magnetoelectric effect. Spin dependent electron
screening is the fundamental mechanism at the microscopic level. We also
predict an electric control of magnetization in this structure. The naturally
broken inversion symmetry in our tri-component structure introduces a
magnetoelectric coupling energy of . Such a magnetoelectric coupling
effect is general in ferromagnet-ferroelectric heterostructures, independent of
particular chemical or physical bonding, and will play an important role in the
field of multiferroics.Comment: 5 pages including 3 figures and 1 tabl
Preface
The University of Pennsylvania Working Papers in Linguistics (PWPL) is an occasional series published by the Penn Linguistics Club, the graduate student organization of the Linguistics Department of the University of Pennsylvania. The series has included volumes of previously unpublished work, or work in progress, by linguists with an ongoing affiliation with the Department, as well as volumes of papers from the NWAVE conference and the Penn Linguistics Colloquium.
The current PWPL series editors are Jim Alexander, Alexis Dimitriadis, Na-‐Rae Han, Elsi Kaiser, Michelle Minnick Fox, Christine Moisset, and Alexander Williams
Preface
The University of Pennsylvania Working Papers in Linguistics (PWPL) is an occasional series published by the Penn Linguistics Club, the graduate student organization of the Linguistics Department of the University of Pennsylvania. The series has included volumes of previously unpublished work, or work in progress, by linguists with an ongoing affiliation with the Department, as well as volumes of papers from the NWAVE conference and the Penn Linguistics Colloquium.
The current PWPL series editors are Jim Alexander, Alexis Dimitriadis, Na-‐Rae Han, Elsi Kaiser, Michelle Minnick Fox, Christine Moisset, and Alexander Williams
Describing many-body localized systems in thermal environments
In this work we formulate an efficient method for the description of
many-body localized systems in weak contact with thermal environments at
temperature . For this purpose we exploit the representation of the system
in terms of quasi-local integrals of motion (-bits) to derive a quantum
master equation using Born-Markov approximations. We show how this equation can
be treated by using quantum-jump Monte-Carlo techniques as well as by deriving
approximate kinetic equations of motion. As an example, we consider the
one-dimensional Anderson model for spinless fermions including also
nearest-neighbor interactions, which we diagonalize approximately by employing
a recently proposed method valid in the limit of strong disorder and weak
interactions. Coupling the system to a global thermal bath, we study the
transport between two leads with different chemical potentials at both of its
ends. We find that the temperature-dependent current is captured by an
interaction-dependent version of Mott's law for variable range hopping, where
transport is enhanced/lowered depending on whether the interactions are
attractive or repulsive, respectively. We interpret these results in terms of
spatio-energetic correlations between the -bits
Air-spun PLA nanofibers modified with reductively-sheddable hydrophilic surfaces for vascular tissue engineering : synthesis and surface modification
Polylactide (PLA) is a class of promising biomaterials that hold great promise for various biological and biomedical applications, particularly in the field of vascular tissue engineering where it can be used as a fibrous mesh to coat the inside of vascular prostheses. However, its hydrophobic surface providing nonspecific interactions and its limited ability to further modifications are challenges that need to be overcome. Here, the development of new air-spun PLA nanofibers modified with hydrophilic surfaces exhibiting reduction response is reported. Surface-initiated atom transfer radical polymerization allows for grafting pendant oligo(ethylene oxide)-containing polymethacrylate (POEOMA) from PLA air-spun fibers labeled with disulfide linkages. The resulting PLA-ss-POEOMA fibers exhibit enhanced thermal stability and improved surface properties, as well as thiol-responsive shedding of hydrophilic POEOMA by the cleavage of its disulfide linkages in response to reductive reactions, thus tuning the surface properties
Spin Manipulation by Creation of Single-Molecule Radical Cations
All-trans-retinoic acid (ReA), a closed-shell organic molecule comprising
only C, H, and O atoms, is investigated on a Au(111) substrate using scanning
tunneling microscopy and spectroscopy. In dense arrays single ReA molecules are
switched to a number of states, three of which carry a localized spin as
evidenced by conductance spectroscopy in high magnetic fields. The spin of a
single molecule may be reversibly switched on and off without affecting its
neighbors. We suggest that ReA on Au is readily converted to a radical by the
abstraction of an electron.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev. Let
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