We report the Meissner effect studies on an FeSe thin film grown on Nb-doped SrTiO₃ substrate by molecular beam epitaxy. Two-coil mutual inductance measurement clearly demonstrates the onset of ...diamagnetic screening at 65 K, which is consistent with the gap opening temperature determined by previous angle-resolved photoemission spectroscopy results. The applied magnetic field causes a broadening of the superconducting transition near the onset temperature, which is the typical behavior for quasi-two-dimensional superconductors. Our results provide direct evidence that FeSe thin film grown on Nb-doped SrTiO₃ substrate has an onset T C ~ 65 K, which is the highest among all iron-based superconductors discovered so far.
Moving academic research forward during COVID-19 Wigginton, N S; Cunningham, R M; Katz, R H ...
Science (American Association for the Advancement of Science),
06/2020, Letnik:
368, Številka:
6496
Journal Article
Recenzirano
Odprti dostop
A gradual, stepwise approach to reopening, informed by public health expertise, will be essential
The coronavirus disease 2019 (COVID-19) pandemic has led to an unprecedented disruption of society. ...Institutions of higher education have been no exception. To preserve the safety of their communities and adhere to public health guidance, universities and colleges around the world have rapidly pivoted to fully online teaching and learning models, implemented remote work for the majority of employees, and shuttered countless public spaces and programs. Most “on-site” research activities—in laboratories, in clinics, or in the field—also ground to a halt. Many institutions are now planning or implementing a ramp-up of on-site research activities, which offers an opportunity to begin implementing policies and practices that will lay the groundwork for the eventual reopening of additional onsite academic programming, including teaching. To ramp up safely, institutions are working with stakeholder groups—such as public health experts, as well as faculty, staff, and students—to develop guiding principles that will help inform and drive decision-making over the coming months. We synthesized several risk and decision-making frameworks under development at our universities to develop a set of criteria informed by public health expertise that institutions should consider before and during the first stages of restoring research activities and less certain factors to consider for subsequent phases.
A magnetic domain boundary on the surface of a three-dimensional topological insulator is predicted to host a chiral edge state, but direct demonstration is challenging. We used a scanning ...superconducting quantum interference device to show that current in a magnetized topological insulator heterostructure (EuS/Bi2Se3) flows at the edge when the Fermi level is gate-tuned to the surface band gap. We further induced micrometer-scale magnetic structures on the heterostructure and detected a chiral edge current at the magnetic domain boundary. The chirality of the current was determined by magnetization of the surrounding domain, and its magnitude by the local chemical potential rather than the applied current. Such magnetic structures provide a platform for detecting topological magnetoelectric effects and may enable progress in quantum information processing and spintronics.
Scanning SQUID susceptometry images the local magnetization and susceptibility of a sample. By accurately modeling the SQUID signal we can determine physical properties such as the penetration depth ...and permeability of superconducting samples. We calculate the scanning SQUID susceptometry signal for a superconducting slab of arbitrary thickness with isotropic London penetration depth lambda on a nonsuperconducting substrate, where both slab and substrate can have a paramagnetic response that is linear in the applied field. We derive analytical approximations to our general expression in a number of limits. Using our results, we fit experimental susceptibility data as a function of the sample-sensor spacing for three samples: (1) delta -doped SrTiO sub(3), which has a predominantly diamagnetic response, (2) a thin film of LaNiO sub(3), which has a predominantly paramagnetic response, and (3) the two-dimensional electron layer at a SrTiO sub(3)/LaAIO sub(3) interface, which exhibits both types of response. These formulas will allow the determination of the concentrations of paramagnetic spins and superconducting carriers from fits to scanning SQUID susceptibility measurements.
Thin film magnetic heterostructures with competing interfacial coupling and Zeeman energy provide a fertile ground to study phase transition between different equilibrium states as a function of ...external magnetic field and temperature. A rare-earth (RE)/transition metal (TM) ferromagnetic multilayer is a classic example where the magnetic state is determined by a competition between the Zeeman energy and antiferromagnetic interfacial exchange coupling energy. Technologically, such structures offer the possibility to engineer the macroscopic magnetic response by tuning the microscopic interactions between the layers. We have performed an exhaustive study of nickel/gadolinium as a model system for understanding RE/TM multilayers using the element-specific measurement technique x-ray magnetic circular dichroism, and determined the full magnetic state diagrams as a function of temperature and magnetic layer thickness. We compare our results to a modified Stoner-Wohlfarth-based model and provide evidence of a thickness-dependent transition to a magnetic fan state which is critical in understanding magnetoresistance effects in RE/TM systems. The results provide important insight for spintronics and superconducting spintronics where engineering tunable magnetic inhomogeneity is key for certain applications.
To evaluate the effect of recombinant humandeoxyribonuclease I (rhDNase) in shortening the length of thehospitalization and improving the chest radiographs (CXRs) inhospitalized infants with ...respiratory syncytial virus (RSV) infectionas a result of its mucolytic properties.
Randomized, double-blind, placebo-controlled investigation of 75patients with RSV bronchiolitis. The study was conducted at the University of Michigan Medical Center and St. Joseph Mercy Hospital, both in Ann Arbor, MI.
The respiratory rate, wheezing, and retraction difference scores, obtained by subtracting thehospital discharge score from the corresponding hospital admissionscore, show no difference between the two groups, but the CXRdifference scores show that the rhDNase group improved by 0.46 whilethe placebo group worsened by 0.60 (p < 0.001). Analysis ofcovariance for the hospital discharge CXR score after adjusting for thehospital admission score for both groups was done. There was adifference in scores between the two groups, with adjusted mean for thestudy group of 2.03, and 2.76 for the placebo group (p < 0.001). Paired t test statistics in each of the two groups werecomputed. For the placebo group, the mean increase of 0.60 wassignificant (p = 0.02), and the mean decrease of 0.46 for the rhDNasegroup was also significant (p = 0.02). A one-way analysis ofcovariance with the hospital discharge CXR scores as the dependentvariable and the hospital admission score as the covariate showed thatthere was a significant difference between the groups(p = 0.01).
In patients with RSVbronchiolitis, there was significant improvement in the CXRs with theuse of rhDNase compared to significant worsening in the placebo group. To our knowledge, this is the first report of the use of rhDNase totreat RSV bronchiolitis.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The temperature dependence of the half-integer magnetic flux quantum effect in thin-film tricrystal samples of the high-critical-temperature cuprate superconductor YBa$_2$Cu$_3$O$_{7-\delta}$ was ...measured and found to persist from a temperature of 0.5 kelvin through a critical temperature of about 90 kelvin, with no change in total flux. This result implies that d-wave symmetry pairing predominates in this cuprate, with a small component of time-reversal symmetry breaking, if any, over the entire temperature range.
Scanning magnetic imaging of Sr2RuO4 BJÖRNSSON, Per G; MAENO, Yoshiteru; HUBER, Martin E ...
Physical review. B, Condensed matter and materials physics,
07/2005, Letnik:
72, Številka:
1
Journal Article
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