5,206 research outputs found
Induced Ferromagnetism at BiFeO3/YBa2Cu3O7 Interfaces
Transition metal oxides (TMOs) exhibit many emergent phenomena ranging from
high-temperature superconductivity and giant magnetoresistance to magnetism and
ferroelectricity. In addition, when TMOs are interfaced with each other, new
functionalities can arise, which are absent in individual components. Here, we
report results from first-principles calculations on the magnetism at the
BiFeO3/YBa2Cu3O7 interfaces. By comparing the total energy for various magnetic
spin configurations inside BiFeO3, we are able to show that a metallic
ferromagnetism is induced near the interface. We further develop an interface
exchange-coupling model and place the extracted exchange coupling interaction
strengths, from the first-principles calculations, into a resultant generic
phase diagram. Our conclusion of interfacial ferromagnetism is confirmed by the
presence of a hysteresis loop in field-dependent magnetization data. The
emergence of interfacial ferromagnetism should have implications to electronic
and transport properties.Comment: 13 pages, 4 figure
REPORTAJE CARMELO ARTILES BOLAÑOS. PRESIDENTE DEL CABILDO DE GC [Material gráfico]
Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201
Codimension Two Branes in Einstein-Gauss-Bonnet Gravity
Codimension two branes play an interesting role in attacking the cosmological
constant problem. Recently, in order to handle some problems in codimension two
branes in Einstein gravity, Bostock {\it et al.} have proposed using
six-dimensional Einstein-Gauss-Bonnet (EGB) gravity instead of six-dimensional
Einstein gravity. In this paper, we present the solutions of codimension two
branes in six-dimensional EGB gravity. We show that Einstein's equations take a
"factorizable" form for a factorized metric tensor ansatz even in the presence
of the higher-derivative Gauss-Bonnet term. Especially, a new feature of the
solution is that the deficit angle depends on the brane geometry. We discuss
the implication of the solution to the cosmological constant problem. We also
comment on a possible problem of inflation model building on codimension two
branes.Comment: 16 pages, no figures. v2: References added; v3: Reference added,
Sec.4 and 5 combined into one; v4: References added, minor corrections, to
appear in Physical Review
Mobility gap in fractional quantum Hall liquids: Effects of disorder and layer thickness
We study the behavior of two-dimensional electron gas in the fractional
quantum Hall regime in the presence of finite layer thickness and correlated
disordered potential. Generalizing the Chern number calculation to many-body
systems, we determine the mobility gaps of fractional quantum Hall states based
on the distribution of Chern numbers in a microscopic model. We find excellent
agreement between experimentally measured activation gaps and our calculated
mobility gaps, when combining the effects of both disordered potential and
layer thickness. We clarify the difference between mobility gap and spectral
gap of fractional quantum Hall states and explain the disorder-driven collapse
of the gap and the subsequent transitions from the fractional quantum Hall
states to insulator.Comment: 13 pages, 8 figure
Boson Star Superradiance
Recently, it has been realized that in some systems internal space rotation
can induce energy amplification for scattering waves, similar to rotation in
real space. Particularly, it has been shown that energy extraction is possible
for a Q-ball, a stationary non-topological soliton that is coherently rotating
in its field space. In this paper, we generalize the analysis to the case of
boson stars, and show that the same energy extraction mechanism still works for
boson stars.Comment: 10 pages, 6 figures; v2: refs added and clarifie
Students with Learning Disabilities, Pair Programming And Situational Motivation
Persons with learning disabilities (LD) are underrepresented in computer science and information technology fields despite the explosion of related career opportunities and interest. In this study, we examine the use of pair programming as a collaborative intervention in with computer programming and compare students with learning disabilities to students who do not have learning disabilities. We concentrate on situational motivation constructs which tap into the desire to meet goals and acquire skills. We find that students with LD and similar students without LD fare the same. For the both groups, three of the four situational motivation subscales increase after the introduction of pair programming. The use of pair programming holds promises as an educational intervention for all students including those with learning disabilities
The Non-local Kardar-Parisi-Zhang Equation With Spatially Correlated Noise
The effects of spatially correlated noise on a phenomenological equation
equivalent to a non-local version of the Kardar-Parisi-Zhang equation are
studied via the dynamic renormalization group (DRG) techniques. The correlated
noise coupled with the long ranged nature of interactions prove the existence
of different phases in different regimes, giving rise to a range of roughness
exponents defined by their corresponding critical dimensions. Finally
self-consistent mode analysis is employed to compare the non-KPZ exponents
obtained as a result of the long range -long range interactions with the DRG
results.Comment: Plain Latex, 10 pages, 2 figures in one ps fil
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