134 research outputs found
Coexistence of spin polarization and pairing correlations in metallic grains
We investigate the competition between magnetic depairing interactions, due to spin-exchange mechanism and∕or to spin-dependent asymmetric bandwidths, and pairing coupling in metallic grains. We present a detailed analysis of the quantum ground state in different regimes arising from the interplay between ferromagnetic and pairing correlations for different fillings. We find out that the occurrence of a ground state with coexisting spin-polarization and pairing correlations is enhanced when the asymmetric spin-dependent distribution of the single-particle energies is considered. The mechanisms leading to such a stable quantum state are finally clarified
Competition between magnetic and superconducting pairing exchange interactions in confined systems
We analyze the competition between magnetic and pairing interactions in confined systems relevant to either small superconducting grains or trapped ultracold atomic gases. The response to the imbalance of the chemical potential for the two spin states leads to various inhomogeneous profiles of the pair energy distribution. We show that the position in the energy spectrum for the unpaired particles can be tuned by varying the filling or the pairing strength. When small grains are considered, the antiferromagnetic exchange stabilizes the pair correlations, whereas for Fermi gases, a transition from a mixed configuration to a phase-separated one beyond a critical polarization threshold appears, as does an unconventional phase with a paired shell around a normal core
Preparation and Physicochemical Properties of 10-Hydroxycamptothecin (HCPT) Nanoparticles by Supercritical Antisolvent (SAS) Process
The goal of the present work was to study the feasibility of 10-hydroxycamptothecin (HCPT) nanoparticle preparation using supercritical antisolvent (SAS) precipitation. The influences of various experimental factors on the mean particle size (MPS) of HCPT nanoparticles were investigated. The optimum micronization conditions are determined as follows: HCPT solution concentration 0.5 mg/mL, the flow rate ratio of CO2 and HCPT solution 19.55, precipitation temperature 35 °C and precipitation pressure 20 MPa. Under the optimum conditions, HCPT nanoparticles with a MPS of 180 ± 20.3 nm were obtained. Moreover, the HCPT nanoparticles obtained were characterized by Scanning electron microscopy, Dynamic light scattering, Fourier-transform infrared spectroscopy, High performance liquid chromatography-mass spectrometry, X-ray diffraction and Differential scanning calorimetry analyses. The physicochemical characterization results showed that the SAS process had not induced degradation of HCPT. Finally, the dissolution rates of HCPT nanoparticles were investigated and the results proved that there is a significant increase in dissolution rate compared to unprocessed HCPT
Black Holes as the source of the dark energy: a stringent test with the high-redshift JWST AGNs
It has been suggested that there is evidence for cosmological coupling of
black holes (BHs) with an index of and hence the BHs serve as the
astrophysical source of the dark energy. The data sample however is limited for
the redshifts . Recently, the James Webb Space Telescope (JWST) has
detected more than 180 high-redshift Active Galactic Nuclei (AGNs) and quasars.
Among the JWST NIRSpec/NIRCam resolved AGNs, three are identified in early-type
host galaxies with a redshift . Their and , however, are in tension with the prediction of the cosmological coupling
of black holes with at a confidence level of , which is not
in support of the hypothesis that BHs serve as the origin of dark energy. The
future observations of high-redshift AGNs by JWST will further test such a
hypothesis by identifying more early-type host galaxies in the higher mass
range.Comment: 9 pages, 3 figures, 1 table; Submitted to ApJL. Comments are welcome
Interface-Induced Superconductivity in Magnetic Topological Insulator-Iron Chalcogenide Heterostructures
When two different electronic materials are brought together, the resultant
interface often shows unexpected quantum phenomena, including interfacial
superconductivity and Fu-Kane topological superconductivity (TSC). Here, we use
molecular beam epitaxy (MBE) to synthesize heterostructures formed by stacking
together two magnetic materials, a ferromagnetic topological insulator (TI) and
an antiferromagnetic iron chalcogenide (FeTe). We discover emergent
interface-induced superconductivity in these heterostructures and demonstrate
the trifecta occurrence of superconductivity, ferromagnetism, and topological
band structure in the magnetic TI layer, the three essential ingredients of
chiral TSC. The unusual coexistence of ferromagnetism and superconductivity can
be attributed to the high upper critical magnetic field that exceeds the Pauli
paramagnetic limit for conventional superconductors at low temperatures. The
magnetic TI/FeTe heterostructures with robust superconductivity and atomically
sharp interfaces provide an ideal wafer-scale platform for the exploration of
chiral TSC and Majorana physics, constituting an important step toward scalable
topological quantum computation.Comment: 14 pages, 4 figures. Accepted by Science. Comments are welcom
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