Superconductivity and magnetism are often antagonistic in quantum matter, although their intertwining has long been considered in frustrated-lattice systems. Here we utilize scanning tunnelling microscopy and muon spin resonance to demonstrate time-reversal symmetry-breaking superconductivity in kagome metal Cs(V, Ta)Sb, where the Cooper pairing exhibits magnetism and is modulated by it. In the magnetic channel, we observe spontaneous internal magnetism in a fully gapped superconducting state.
View Article and Find Full Text PDFDespite decades of research in spatially confined superconducting systems to understand the modification of superconductivity from reduced length scales, the investigation of the quantum confinement effect on high-temperature superconductors remains an outstanding challenge. Here, we report scanning tunneling spectroscopy measurements on laterally confined FeSe monolayers on SrTiO substrates, which are formed by epitaxially growing FeSe films with a coverage less than one unit cell. Comparing to the uniform regions of FeSe monolayers, the peninsula regions at the monolayer boundary exhibit reduced Fermi energy and undiminished superconductivity, leading to a putative crossover from a Bardeen-Cooper-Schrieffer state to a Bose-Einstein condensate state.
View Article and Find Full Text PDFVisualizing atomic-orbital degrees of freedom is a frontier challenge in scanned microscopy. Some types of orbital order are virtually imperceptible to normal scattering techniques because they do not reduce the overall crystal lattice symmetry. A good example is d/d (π,π) orbital order in tetragonal lattices.
View Article and Find Full Text PDFThe iron-based superconductors are an ideal platform to reveal the enigma of the unconventional superconductivity and potential topological superconductivity. Among them, the monolayer Fe(Se,Te)/SrTiO(001), which is proposed to be topological nontrivial, shows interface-enhanced high-temperature superconductivity in the two-dimensional limit. However, the experimental studies on the superconducting pairing mechanism of monolayer Fe(Se,Te) films are still limited.
View Article and Find Full Text PDFThe discovery of superconductivity in infinite-layer nickelates has added a new family of materials to the fascinating growing class of unconventional superconductors. By incorporating the strongly correlated multiorbital nature of the low-energy electronic degrees of freedom, we compute the leading superconducting instability from magnetic fluctuations relevant for infinite-layer nickelates. Specifically, by properly including the doping dependence of the Ni d_{x^{2}-y^{2}} and d_{z^{2}} orbitals as well as the self-doping band, we uncover a transition from d-wave pairing symmetry to nodal s_{±} superconductivity, driven by strong fluctuations in the d_{z^{2}}-dominated orbital states.
View Article and Find Full Text PDFFor multiband superconductors, the orbital multiplicity yields orbital differentiation in normal-state properties and can lead to orbital-selective spin-fluctuation Cooper pairing. The orbital-selective phenomenon has become increasingly pivotal in clarifying the pairing "enigma", particularly for multiband high-temperature superconductors. Meanwhile, in one-unit-cell (1-UC) FeSe/SrTiO, since the standard electron-hole Fermi pocket nesting scenario is inapplicable, the actual pairing mechanism is subject to intense debate.
View Article and Find Full Text PDFCultural intelligence is one's ability to adapt when confronted with problems arising in interactions with people or artifacts of diverse cultures. In this study, we conduct an initial construct-validation and assessment of a maximum-performance test of cultural intelligence. We assess the psychometric properties of the test and also correlate the test with other measures with which it might be expected there would be some connection.
View Article and Find Full Text PDFAbdominal wall actinomycosis is a very rare infection caused by anaerobic Gram-positive bacteria Actinomyces. We present a case of a 72-year-old female with chronic pain located in the right hypochondriac region and anterior abdominal wall mass which had developed six months before. An ultrasonography (USG) and computed tomography (CT) scan of the abdomen were performed and showed an inflammatory change with a strong internal linear reflection in the right upper abdomen.
View Article and Find Full Text PDFBackground: Women diagnosed with substance use disorders (SUDs) have higher rates of major medical conditions compared to women without SUDs. Cervical cancer is the second leading cause of cancer death in women aged 20-39 years worldwide and women with SUDs have an increased risk of cervical cancer compared to women without SUD. The National Drug Treatment Centre (NDTC) cervical screening programme, derived from the national CervicalCheck programme, offers free cervical screening to patients attending for treatment of SUDs.
View Article and Find Full Text PDFWe report the optical detection of magnons with a broad range of wavevectors in magnetic insulator YFeO thin films by proximate nitrogen-vacancy (NV) single-spin sensors. Through multimagnon scattering processes, the excited magnons generate fluctuating magnetic fields at the NV electron spin resonance frequencies, which accelerate the relaxation of NV spins. By measuring the variation of the emitted spin-dependent photoluminescence of the NV centers, magnons with variable wavevectors up to ∼5 × 10 m can be optically accessed, providing an alternative perspective to reveal the underlying spin behaviors in magnetic systems.
View Article and Find Full Text PDFUnderstanding the origin of the magnetism of high temperature superconductors is crucial for establishing their unconventional pairing mechanism. Recently, theory predicts that FeSe is close to a magnetic quantum critical point, and thus weak perturbations such as impurities could induce local magnetic moments. To elucidate such quantum instability, we have employed scanning tunneling microscopy and spectroscopy.
View Article and Find Full Text PDFBogoliubov Fermi surfaces are contours of zero-energy excitations that are protected in the superconducting state. Here we show that multiband superconductors with dominant spin singlet, intraband pairing of spin-1/2 electrons can undergo a transition to a state with Bogoliubov Fermi surfaces if spin-orbit coupling, interband pairing and time reversal symmetry breaking are also present. These latter effects may be small, but drive the transition to the topological state for appropriate nodal structure of the intra-band pair.
View Article and Find Full Text PDFThe interplay between unconventional Cooper pairing and quantum states associated with atomic scale defects is a frontier of research with many open questions. So far, only a few of the high-temperature superconductors allow this intricate physics to be studied in a widely tunable way. We use scanning tunneling microscopy to image the electronic impact of Co atoms on the ground state of the LiFe_{1-x}Co_{x}As system.
View Article and Find Full Text PDFThe ^{36}Ar(n,γ)^{37}Ar (t_{1/2}=35 d) and ^{38}Ar(n,γ)^{39}Ar (269 yr) reactions were studied for the first time with a quasi-Maxwellian (kT∼47 keV) neutron flux for Maxwellian average cross section (MACS) measurements at stellar energies. Gas samples were irradiated at the high-intensity Soreq applied research accelerator facility-liquid-lithium target neutron source and the ^{37}Ar/^{36}Ar and ^{39}Ar/^{38}Ar ratios in the activated samples were determined by accelerator mass spectrometry at the ATLAS facility (Argonne National Laboratory). The ^{37}Ar activity was also measured by low-level counting at the University of Bern.
View Article and Find Full Text PDFIron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious.
View Article and Find Full Text PDFThe superconductor iron selenide (FeSe) is of intense interest owing to its unusual nonmagnetic nematic state and potential for high-temperature superconductivity. But its Cooper pairing mechanism has not been determined. We used Bogoliubov quasiparticle interference imaging to determine the Fermi surface geometry of the electronic bands surrounding the Γ = (0, 0) and = (π/, 0) points of FeSe and to measure the corresponding superconducting energy gaps.
View Article and Find Full Text PDFSpin fluctuations are a leading candidate for the pairing mechanism in high temperature superconductors, supported by the common appearance of a distinct resonance in the spin susceptibility across the cuprates, iron-based superconductors and many heavy fermion materials. The information we have about the spin resonance comes almost exclusively from neutron scattering. Here we demonstrate that by using low-temperature scanning tunnelling microscopy and spectroscopy we can characterize the spin resonance in real space.
View Article and Find Full Text PDFIntroduction: In cases of haemorrhoidal disease resistant to conservative treatment, surgical treatment is necessary to relieve the symptoms.
Aim: To investigate the current methods used by Polish surgeons.
Material And Methods: Surveys were distributed to members of the Association of Polish Surgeons (APS), in which participants were asked a number of closed-ended questions regarding haemorrhoidal disease and the way they treated suffering patients.
A free surface liquid-lithium jet target is operating routinely at Soreq Applied Research Accelerator Facility (SARAF), bombarded with a ~1.91 MeV, ~1.2 mA continuous-wave narrow proton beam.
View Article and Find Full Text PDFWe provide a band structure with low-energy properties consistent with recent photoemission and quantum oscillation measurements on FeSe, assuming mean-field-like site- and/or bond-centered ferro-orbital ordering at the structural transition. We show how the resulting model provides a consistent explanation of the temperature dependence of the measured Knight shift and the spin-relaxation rate. Furthermore, the superconducting gap structure obtained from spin-fluctuation theory exhibits nodes on the electron pockets, consistent with the V-shaped density of states obtained by tunneling spectroscopy on this material, and the temperature dependence of the London penetration depth.
View Article and Find Full Text PDFWe apply a recently developed method combining first principles based Wannier functions with solutions to the Bogoliubov-de Gennes equations to the problem of interpreting STM data in cuprate superconductors. We show that the observed images of Zn on the surface of Bi_{2}Sr_{2}CaCu_{2}O_{8} can only be understood by accounting for the tails of the Cu Wannier functions, which include significant weight on apical O sites in neighboring unit cells. This calculation thus puts earlier crude "filter" theories on a microscopic foundation and solves a long-standing puzzle.
View Article and Find Full Text PDFIn superconductors with unconventional pairing mechanisms, the energy gap in the excitation spectrum often has nodes, which allow quasiparticle excitations at low energies. In many cases, such as in d-wave cuprate superconductors, the position and topology of nodes are imposed by the symmetry, and thus the presence of gapless excitations is protected against disorder. Here we report on the observation of distinct changes in the gap structure of iron-pnictide superconductors with increasing impurity scattering.
View Article and Find Full Text PDFThe free-surface Liquid-Lithium Target, recently developed at Soreq Applied Research Accelerator Facility (SARAF), was successfully used with a 1.9 MeV, 1.2 mA (2.
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