Imaging stray magnetic field of individual ferromagnetic nanotubes

We use a scanning nanometer-scale superconducting quantum interference device to map the stray magnetic field produced by individual ferromagnetic nanotubes (FNTs) as a function of applied magnetic field. The images are taken as each FNT is led through magnetic reversal and are compared with micromagnetic simulations, which correspond to specific magnetization configurations. In magnetic fields applied perpendicular to the FNT long axis, their magnetization appears to reverse through vortex states, i.e.\ configurations with vortex end domains or -- in the case of a sufficiently short FNT -- with a single global vortex. Geometrical imperfections in the samples and the resulting distortion of idealized mangetization configurations influence the measured stray-field patterns.Comment: 14 pages, 4 figure

Effectiveness of Class IC Antiarrhythmics in Patients with Paroxysmal Form of Atrial Fibrillation in Absence of Structural Heart Disease

Aim. To study the efficacy of class IC arrhythmic drugs (AAD) and catheter ablation (CA) for paroxysmal form of atrial fibrillation (AF) in patients with without structural heart disease.Material and methods. The study included 122 patients (44 men, 78 women, mean age 63 [55;68] years) with symptomatic AF paroxysms. Patients was divided into the lappaconitine hydrobromide group (LH group; n=26), the propafenone group (P group; n=25) – 25 patients, the diethylaminopropionylethoxycarbonylaminophenothiazine hydrochloride (DH group; n=23), the CA groups: radiofrequency ablation (RFA group; n=24) and cryoballoon ablation (CRYO group; n=24) groups each included 24 patients. The primary endpoint was the AF recurrence within 6 and 12 months from the onset of antiarrhythmic drug therapyand in RFA and CRYO groups – within 6 and 12 months after the end of the blinding period. Additionally, in AAD groups a composite endpoint was assessed: the frequency of recurrence of AF within 6 months and the frequency of side effects requiring drug withdrawal.Results. Within the 6 months AF recurrence was observed in 13 (50%) patients of the LH group, 11 (44%) patients of the P group, and 13 (56.5%) patients of the DH group (p=0.687). Side effects requiring drug withdrawal were observed in the LH group in 2 patients (7.7%), in the P group in 3 patients (12%) and in the DH group in 3 patients (13%) (p=0.801). The difference in frequency of reaching the composite endpoint was not significant (p = 0.581) and the incidence was 57.7%, 56%, 69.5%, respectively in groups LH, P and DH. The efficacy of CA was higher than class IC AADs: 77% vs 39% (that including the withdrawals of AADs due to side effects) (p˂0.001). At the same time, there was no significant difference in the effectiveness of RFA and CRYO: AF recurrences within 6 months after the end of the blinding period were registered in the RFA group in 29% of cases, in the CRYO group – in 16.7% of cases (p=0.247). The overall effectiveness of CA after 12 months was 69%, which was significantly higher than the effectiveness of AADs that was 38% (p˂0.001).Conclusion. Starting the AAD therapy with IC class in patients with paroxysmal AF in the absence of structural pathology, despite acceptable safety, one should take into account that, regardless of the initially prescribed drug, less than half of patients can achieve prevention of AF recurrence within 1 year. CA for AF can be considered as a first line therapy or can be recommended if one of IC class AADs is ineffective

Nano-sized SQUID-on-tip for scanning probe microscopy

We present a SQUID of novel design, which is fabricated on the tip of a pulled quartz tube in a simple 3-step evaporation process without need for any additional processing, patterning, or lithography. The resulting devices have SQUID loops with typical diameters in the range 75–300 nm. They operate in magnetic fields up to 0.6 T and have flux sensitivity of 1.8 μΦ0/Hz1/2 and magnetic field sensitivity of 10−7 T/Hz1/2, which corresponds to a spin sensitivity of 65 μB/Hz1/2 for aluminum SQUIDs. The shape of the tip and the small area of the SQUID loop, together with its high sensitivity, make our device an excellent tool for scanning SQUID microscopy: With the SQUID-on-tip glued to a tine of a quartz tuning fork, we have succeeded in obtaining magnetic images of a patterned niobium film and of vortices in a superconducting film in a magnetic field.Physic

Quantitative nanoscale vortex-imaging using a cryogenic quantum magnetometer

Microscopic studies of superconductors and their vortices play a pivotal role in our understanding of the mechanisms underlying superconductivity. Local measurements of penetration depths or magnetic stray-fields enable access to fundamental aspects of superconductors such as nanoscale variations of superfluid densities or the symmetry of their order parameter. However, experimental tools, which offer quantitative, nanoscale magnetometry and operate over the large range of temperature and magnetic fields relevant to address many outstanding questions in superconductivity, are still missing. Here, we demonstrate quantitative, nanoscale magnetic imaging of Pearl vortices in the cuprate superconductor YBCO, using a scanning quantum sensor in form of a single Nitrogen-Vacancy (NV) electronic spin in diamond. The sensor-to-sample distance of ~10nm we achieve allows us to observe striking deviations from the prevalent monopole approximation in our vortex stray-field images, while we find excellent quantitative agreement with Pearl's analytic model. Our experiments yield a non-invasive and unambiguous determination of the system's local London penetration depth, and are readily extended to higher temperatures and magnetic fields. These results demonstrate the potential of quantitative quantum sensors in benchmarking microscopic models of complex electronic systems and open the door for further exploration of strongly correlated electron physics using scanning NV magnetometry.Comment: Main text (5 pages, 4 figures) plus supplementary material (5 pages, 6 figures). Comments welcome. Further information under http://www.quantum-sensing.c

Studies of new Higgs boson interactions through nonresonant HH production in the b¯bγγ fnal state in pp collisions at √s = 13 TeV with the ATLAS detector

A search for nonresonant Higgs boson pair production in the b ¯bγγ fnal state is performed using 140 fb−1 of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. This analysis supersedes and expands upon the previous nonresonant ATLAS results in this fnal state based on the same data sample. The analysis strategy is optimised to probe anomalous values not only of the Higgs (H) boson self-coupling modifer κλ but also of the quartic HHV V (V = W, Z) coupling modifer κ2V . No signifcant excess above the expected background from Standard Model processes is observed. An observed upper limit µHH < 4.0 is set at 95% confdence level on the Higgs boson pair production cross-section normalised to its Standard Model prediction. The 95% confdence intervals for the coupling modifers are −1.4 < κλ < 6.9 and −0.5 < κ2V < 2.7, assuming all other Higgs boson couplings except the one under study are fxed to the Standard Model predictions. The results are interpreted in the Standard Model efective feld theory and Higgs efective feld theory frameworks in terms of constraints on the couplings of anomalous Higgs boson (self-)interactions

Search for non-resonant Higgs boson pair production in the 2b+2l+ETmiss final state in pp collisions at s = 13 TeV with the ATLAS detector

A search for non-resonant Higgs boson pair (HH) production is presented, in which one of the Higgs bosons decays to a b-quark pair (bb ̄) and the other decays to WW*, ZZ*, or τ+τ−, with in each case a final state with l+l−+ neutrinos (l = e, μ). The analysis targets separately the gluon-gluon fusion and vector boson fusion production modes. Data recorded by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb−1, are used in this analysis. Events are selected to have exactly two b-tagged jets and two leptons with opposite electric charge and missing transverse momentum in the final state. These events are classified using multivariate analysis algorithms to separate the HH events from other Standard Model processes. No evidence of the signal is found. The observed (expected) upper limit on the cross-section for non-resonant Higgs boson pair production is determined to be 9.7 (16.2) times the Standard Model prediction at 95% confidence level. The Higgs boson self-interaction coupling parameter κλ and the quadrilinear coupling parameter κ2V are each separately constrained by this analysis to be within the ranges [−6.2, 13.3] and [−0.17, 2.4], respectively, at 95% confidence level, when all other parameters are fixed