4,077 research outputs found
Spin-Orbit Coupling in LaAlO/SrTiO interfaces: Magnetism and Orbital Ordering
The combination of Rashba spin-orbit coupling and electron correlations can
induce unusual phenomena in the metallic interface between SrTiO and
LaAlO. We consider effects of Rashba spin-orbit coupling at this interface
in the context of the recent observation of anisotropic magnetism. Firstly, we
show how Rashba spin-orbit coupling in a system near a band-edge can account
for the observed magnetic anisotropy. Secondly, we investigate the coupling
between in-plane magnetic-moment anisotropy and nematicity in the form of an
orbital imbalance between d / d orbitals. We estimate this
coupling to be substantial in the low electron density regime. Such an orbital
ordering can affect magneto transport
Commensurate period Charge Density Modulations throughout the Pseudogap Regime
Theories based upon strong real space (r-space) electron electron
interactions have long predicted that unidirectional charge density modulations
(CDM) with four unit cell (4) periodicity should occur in the hole doped
cuprate Mott insulator (MI). Experimentally, however, increasing the hole
density p is reported to cause the conventionally defined wavevector of
the CDM to evolve continuously as if driven primarily by momentum space
(k-space) effects. Here we introduce phase resolved electronic structure
visualization for determination of the cuprate CDM wavevector. Remarkably, this
new technique reveals a virtually doping independent locking of the local CDM
wavevector at throughout the underdoped phase diagram of the
canonical cuprate . These observations have significant
fundamental consequences because they are orthogonal to a k-space (Fermi
surface) based picture of the cuprate CDM but are consistent with strong
coupling r-space based theories. Our findings imply that it is the latter that
provide the intrinsic organizational principle for the cuprate CDM state
Topological Defects Coupling Smectic Modulations to Intra-unit-cell Nematicity in Cuprate
We study the coexisting smectic modulations and intra-unit-cell nematicity in
the pseudogap states of underdoped Bi2Sr2CaCu2O8+{\delta}. By visualizing their
spatial components separately, we identified 2\pi topological defects
throughout the phase-fluctuating smectic states. Imaging the locations of large
numbers of these topological defects simultaneously with the fluctuations in
the intra-unit-cell nematicity revealed strong empirical evidence for a
coupling between them. From these observations, we propose a Ginzburg-Landau
functional describing this coupling and demonstrate how it can explain the
coexistence of the smectic and intra-unit-cell broken symmetries and also
correctly predict their interplay at the atomic scale. This theoretical
perspective can lead to unraveling the complexities of the phase diagram of
cuprate high-critical-temperature superconductors
Production of conductive bacterial cellulose-polyaniline membranes in the presence of metal salts
This study presents a cost-effective method of enhancing the electrical conductivity and washing durability of bacterial cellulose (BC)-polyaniline (PANI) membrane by the addition of metal salt. In this study, two types of metal salts were tested: copper (II) sulfate and iron (II) sulfate. The optimal condition to produce BC-PANI-metal salt membranes was 0.05% (w/v) of copper (II) sulfate (copper salt). X-ray diffraction analysis showed that the crystallinity of BC-PANI increased after adding copper salt. According to the increased degree of crystallinity, the polymer chain structure of BC-PANI-copper salt (BC-PANI-Cu) was more organized than that of BC-PANI, as confirmed by scanning electron microscopy. In addition, this ordered structure of BC-PANI-Cu indicated enhanced electrical conductivity. Moreover, the addition of copper salt improved the electrical conductivity of BC-PANI to a level about 3.8 times higher than that of BC-PANI produced without metal salt, and it retained about 40% of its original electrical conductivity after three washing cycles. From the results, the addition of copper salt improved both the electrical conductivity and washing durability of the BC-PANI membrane.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (No. NRF-2019R1A2C1009217).info:eu-repo/semantics/publishedVersio
Graphene as an electronic membrane
Experiments are finally revealing intricate facts about graphene which go
beyond the ideal picture of relativistic Dirac fermions in pristine two
dimensional (2D) space, two years after its first isolation. While observations
of rippling added another dimension to the richness of the physics of graphene,
scanning single electron transistor images displayed prevalent charge
inhomogeneity. The importance of understanding these non-ideal aspects cannot
be overstated both from the fundamental research interest since graphene is a
unique arena for their interplay, and from the device applications interest
since the quality control is a key to applications. We investigate the membrane
aspect of graphene and its impact on the electronic properties. We show that
curvature generates spatially varying electrochemical potential. Further we
show that the charge inhomogeneity in turn stabilizes ripple formation.Comment: 6 pages, 11 figures. Updated version with new results about the
re-hybridization of the electronic orbitals due to rippling of the graphene
sheet. The re-hybridization adds the next-to-nearest neighbor hopping effect
discussed in the previous version. New reference to recent STM experiments
that give support to our theor
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Application of observation operators for field scale soil moisture averages and variances in agricultural landscapes
Scale difference between in situ and remotely sensed soil moisture observations and model grid size has been an issue for validation of remote sensing data, soil moisture data assimilation and calibration of hydrologic models. This study aims to link two different scales of soil moisture estimates by upscaling single point measurements to field averages for representing field-scale agricultural areas (∼2 ha) located within the Upper Cedar Creek Watershed in northeastern Indiana. Several statistical methods, mainly focusing on cumulative distribution function (CDF) matching, are tested to upscale point measurements to spatially representative soil moisture. These transforming equations are termed observation operators. The CDF matching is found to be the most successful upscaling method followed by the mean relative difference method using temporally stable point measurements. This study also tests the temporal and spatial (horizontal and vertical) transferability of the different observation operators. Results indicate that the two observation operators from the CDF matching approach and the mean relative difference method using a temporally stable location are transferable in space, but not in time. Rainfall characteristic is most likely the dominant factor affecting the success of observation operator transferability. In addition, the CDF matching approach is found to be an effective method to deduce spatial variability (standard deviation) of soil moisture from single point measurements
The Dendritic magnetic avalanches in carbon-free MgB thin films with and without a deposited Au layer
From the magneto optics images (MOI), the dendritic magnetic avalanche is
known to appear dominantly for thin films of the newly discovered MgB. To
clarify the origin of this phenomenon, we studied in detail the MOI of
carbon-free MgB thin films with and without a deposited gold layer. The MOI
indicated carbon contamination was not the main source of the avalanche. The
MOI clearly showed that the deposition of metallic gold deposition on top of a
MgB thin film improved its thermal stability and suppressed the sudden
appearance of the dendritic flux avalanche. This is consistent with the
previous observation of flux noise in the magnetization.Comment: 9 pages, 4 figeure
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