1,166 research outputs found
Gapped spin liquid with -topological order for kagome Heisenberg model
We apply symmetric tensor network state (TNS) to study the nearest neighbor
spin-1/2 antiferromagnetic Heisenberg model on Kagome lattice. Our method keeps
track of the global and gauge symmetries in TNS update procedure and in tensor
renormalization group (TRG) calculation. We also introduce a very sensitive
probe for the gap of the ground state -- the modular matrices, which can also
determine the topological order if the ground state is gapped. We find that the
ground state of Heisenberg model on Kagome lattice is a gapped spin liquid with
the -topological order (or toric code type), which has a long
correlation length unit cell length. We justify that the TRG
method can handle very large systems with over thousands of spins. Such a long
explains the gapless behaviors observed in simulations on smaller systems
with less than 300 spins or shorter than 10 unit cell length. We also discuss
experimental implications of the topological excitations encoded in our
symmetric tensors.Comment: 10 pages, 7 figure
Septic Cavernous Sinus Thrombosis: An Unusual and Fatal Disease
BackgroundSeptic cavernous sinus thrombosis (CST) is a rare and fatal disease. Clinical presentations in the early stage are nonspecific, and the sensitivity of cranial axial computed tomography (CT) with thick section is low. This study analyzed the clinical manifestation and neuroimaging findings in patients with septic CST in a medical center in Taiwan.MethodsThis retrospective case series included nine patients with septic CST who had typical symptoms and clinical course, evidence of infection, and imaging studies which demonstrated cavernous sinus lesion, and who were treated between 1995 and 2003 at National Taiwan University Hospital.ResultsSeven (77.8 %) patients were more than 50 years old. Five (55.6%) had diabetes, and three (33.3%) had hematologic diseases. All cases were associated with paranasal sinusitis. The most frequent initial symptom was headache (66.7%), followed by ophthalmic complaints (diplopia or ophthalmoplegia, 55.6%; blurred vision or blindness, 55.6%), and ptosis (44.4%). Initial cranial images failed to identify CTS in all patients. Subsequent magnetic resonance imaging (MRI) or coronal contrast-enhanced CT (CECT) with thin section confirmed the diagnosis. Fungi were the most common pathogens (55.6%). The inhospital case-fatality rate was high (44.4%).ConclusionDue to the high case-fatality rate and low yield rate of blood cultures, fungal CST should be suspected in an immunocompromised patient with ophthalmic complaints that progress from one eye to the other. Coronal thin-section CECT may be a useful alternative to MRI as a diagnostic modality for this condition
Superconductivity and vortex structure on BiTe/FeTeSe heterostructures with different thickness of BiTe films
Using scanning tunnel microscopy (STM), we investigate the superconductivity
and vortex properties in topological insulator BiTe thin films
grown on the iron-based superconductor FeTeSe. The
proximity-induced superconductivity weakens in the BiTe film when
the thickness of the film increases. Unlike the elongated shape of vortex cores
observed in the BiTe film with 2-quintuple-layer (QL) thickness,
the isolated vortex cores exhibit a star shape with six rays in the 1-QL film,
and the rays are along the crystalline axes of the film. This is consistent
with the sixfold rotational symmetry of the film lattice, and the
proximity-induced superconductivity is still topologically trivial in the 1-QL
film. At a high magnetic field, when the direction between the two nearest
neighbored vortices deviates from that of any crystalline axes, two cores
connect each other by a pair of adjacent rays, forming a new type of electronic
structure of vortex cores. On the 3-QL film, the vortex cores elongate along
one of the crystalline axes of the BiTe film, similar to the
results obtained on 2-QL films. The elongated vortex cores indicate a twofold
symmetry of the superconducting gap induced by topological superconductivity
with odd parity. This observation confirms possible topological
superconductivity in heterostructures with a thickness of more than 2 QLs. Our
results provide rich information for the vortex cores and vortex-bound states
on the heterostructures consisting of the topological insulator and the
iron-based superconductor.Comment: 8 pages, 8 figure
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