141 research outputs found
Unusual Fermi Surface Sheet-Dependent Band Splitting in Sr2RuO4 Revealed by High Resolution Angle-Resolved Photoemission
High resolution angle-resolved photoemission measurements have been carried
out on Sr2RuO4. We observe clearly two sets of Fermi surface sheets near the
(\pi,0)-(0,\pi) line which are most likely attributed to the surface and bulk
Fermi surface splitting of the \beta band. This is in strong contrast to the
nearly null surface and bulk Fermi surface splitting of the \alpha band
although both have identical orbital components. Extensive band structure
calculations are performed by considering various scenarios, including
structural distortion, spin-orbit coupling and surface ferromagnetism. However,
none of them can explain such a qualitative difference of the surface and bulk
Fermi surface splitting between the \alpha and \beta sheets. This unusual
behavior points to an unknown order on the surface of Sr2RuO4 that remains to
be uncovered. Its revelation will be important for studying and utilizing novel
quantum phenomena associated with the surface of Sr2RuO4 as a result of its
being a possible p-wave chiral superconductor and a topological superconductor.Comment: 13 pages, 4 figure
Flat optical conductivity in topological kagome magnet TbMnSn
Kagome magnet TbMnSn is a new type of topological material that is
known to support exotic quantum magnetic states. Experimental work has
identified that TbMnSn hosts Dirac electronic states that could lead to
topological and Chern quantum phases, but the optical response of the Dirac
fermions of TbMnSn and its properties remain to be explored. Here, we
perform optical spectroscopy measurement combined with first-principles
calculations on single-crystal sample of TbMnSn to investigate the
associated exotic phenomena. TbMnSn exhibits a frequency-independent
optical conductivity spectra in a broad range from 1800 to 3000 cm
(220-370 meV) in experiments. The theoretical band structures and optical
conductivity spectra are calculated with several shifted Fermi energy to
compare with the experiment. The theoretical spectra with 0.56 eV shift for
Fermi energy are well consistent with our experimental results. Besides, the
massive quasi-two-dimensional (quasi-2D) Dirac bands, which have linear band
dispersion in - plane and no band dispersion along the
direction, exist close to the shifted Fermi energy. According to tight-bond
model analysis, we find that quasi-2D Dirac bands give rise to a flat optical
conductivity, while its value is smaller than the result by calculations and
experiments. It indicates that the other trivial bands also contribute to the
flat optical conductivity
Effect of Cleaving Temperature on the Surface and Bulk Fermi Surface of Sr2RuO4 Investigated by High Resolution Angle-Resolved Photoemission
High resolution angle-resolved photoemission measurements are carried out to
systematically investigate the effect of cleaving temperature on the electronic
structure and Fermi surface of SrRuO. Different from previous reports
that high cleaving temperature can suppress surface Fermi surface, we find that
the surface Fermi surface remains obvious and strong in SrRuO cleaved
at high temperature, even at room temperature. This indicates that cleaving
temperature is not a key effective factor in suppressing the surface bands. On
the other hand, in the aged surface of SrRuO that is cleaved and held
for a long time, the bulk bands can be enhanced. We have also carried out laser
ARPES measurements on SrRuO by using vacuum ultra-violet laser (photon
energy at 6.994 eV) and found an obvious enhancement of bulk bands even for
samples cleaved at low temperature. These information are important in
realizing an effective approach in manipulating and detecting the surface and
bulk electronic structure of SrRuO. In particular, the enhancement of
bulk sensitivity, together with its super-high instrumental resolution of VUV
laser ARPES, will be advantageous in investigating fine electronic structure
and superconducting properties of SrRuO in the future
Semantic Segmentation of Histopathological Slides for the Classification of Cutaneous Lymphoma and Eczema
Mycosis fungoides (MF) is a rare, potentially life threatening skin disease,
which in early stages clinically and histologically strongly resembles Eczema,
a very common and benign skin condition. In order to increase the survival
rate, one needs to provide the appropriate treatment early on. To this end, one
crucial step for specialists is the evaluation of histopathological slides
(glass slides), or Whole Slide Images (WSI), of the patients' skin tissue. We
introduce a deep learning aided diagnostics tool that brings a two-fold value
to the decision process of pathologists. First, our algorithm accurately
segments WSI into regions that are relevant for an accurate diagnosis,
achieving a Mean-IoU of 69% and a Matthews Correlation score of 83% on a novel
dataset. Additionally, we also show that our model is competitive with the
state of the art on a reference dataset. Second, using the segmentation map and
the original image, we are able to predict if a patient has MF or Eczema. We
created two models that can be applied in different stages of the diagnostic
pipeline, potentially eliminating life-threatening mistakes. The classification
outcome is considerably more interpretable than using only the WSI as the
input, since it is also based on the segmentation map. Our segmentation model,
which we call EU-Net, extends a classical U-Net with an EfficientNet-B7 encoder
which was pre-trained on the Imagenet dataset.Comment: Submitted to
https://link.springer.com/chapter/10.1007/978-3-030-52791-4_
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