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The superconductivity in systems containing dispersionless (flat) bands is seemingly paradoxical, as traditional Bardeen-Cooper-Schrieffer theory requires an infinite enhancement of the carrier masses. However, the combination of flat and steep (dispersive) bands within the multiple band scenario might boost superconducting responses, potentially explaining high-temperature superconductivity in cuprates and metal hydrides. Here, we report on the magnetic penetration depths, the upper critical field, and the specific heat measurements, together with the first-principles calculations for the Mo5Si3−xPx superconducting family. The band structure features a flat band that gradually approaches the Fermi level as a function of phosphorus doping x, reaching the Fermi level at x ≃ 1.3. This leads to an abrupt change in nearly all superconducting quantities. The superfluid density data placed on the ’Uemura plot‘ results in two separated branches, thus indicating that the emergence of a flat band enhances correlations between conducting electrons.R. Khasanov et al. report thermodynamic and muon-spin-rotation measurements on the Mo5Si3−xPx superconducting family. They find that a flat band reaches the Fermi level at x ≃ 1.3, leading to enhancement of electronic correlations and an abrupt change of the superconducting properties. [ABSTRACT FROM AUTHOR]

The newly discovered kagome superconductors represent a promising platform for investigating the interplay between band topology, electronic order and lattice geometry1–9. Despite extensive research efforts on this system, the nature of the superconducting ground state remains elusive10–17. In particular, consensus on the electron pairing symmetry has not been achieved so far18–20, in part owing to the lack of a momentum-resolved measurement of the superconducting gap structure. Here we report the direct observation of a nodeless, nearly isotropic and orbital-independent superconducting gap in the momentum space of two exemplary CsV3Sb5-derived kagome superconductors—Cs(V0.93Nb0.07)3Sb5 and Cs(V0.86Ta0.14)3Sb5—using ultrahigh-resolution and low-temperature angle-resolved photoemission spectroscopy. Remarkably, such a gap structure is robust to the appearance or absence of charge order in the normal state, tuned by isovalent Nb/Ta substitutions of V. Our comprehensive characterizations of the superconducting gap provide indispensable information on the electron pairing symmetry of kagome superconductors, and advance our understanding of the superconductivity and intertwined electronic orders in quantum materials.The authors report that with the use of angle-resolved photoemission spectroscopy, nodeless electron pairing in CsV3Sb5-derived kagome superconductors can be observed directly. [ABSTRACT FROM AUTHOR]

A knob bow fibula (Bügelknopffibel) of the Leutkirch type, which typologically belongs to the second half of the 4th and early 5th century CE, was excavated in 2018 in the Roman city of Augusta Raurica, present-day Kaiseraugst (AG, Switzerland). This was analyzed for the first time for its elemental composition by using the non-destructive technique of Muon Induced X-ray Emission (MIXE) in the continuous muon beam facility at the Paul Scherrer Institute (PSI). In the present work, the detection limit is 0.4 wt% with ∼ 1.5 hours of measurement time. The fibula was measured at six different positions, at a depth of 0.3–0.4 mm inside the material. The experimental results show that the fibula is made of bronze, containing the main elements copper (Cu), zinc (Zn), tin (Sn) and lead (Pb). The compositional similarities/differences between different parts of the fibula reveal that it was manufactured as two "workpieces". One workpiece consists of the knob (13.0±0.6 wt% Pb), bow (11.9±0.4 wt% Pb) and foot (12.5 ± 0.9 wt% Pb). These show a higher Pb content, suggesting a cast bronze. The spiral (3.2 ± 0.2 wt% Pb), which is part of the other workpiece, has a comparatively lower Pb content, suggesting a forged bronze. [ABSTRACT FROM AUTHOR]

The kagome metals of the family AV3Sb5, featuring a unique structural motif, harbor an array of intriguing phenomena such as chiral charge order and superconductivity. CsV3Sb5 is of particular interest because it displays a double superconducting dome in the region of the temperature-pressure phase diagram where charge order is still present. However, the microscopic origin of such an unusual behavior remains an unsolved issue. Here, to address it, we combine high-pressure, low-temperature muon spin relaxation/rotation with first-principles calculations. We observe a pressure-induced threefold enhancement of the superfluid density, which also displays a double-peak feature, similar to the superconducting critical temperature. This leads to three distinct regions in the phase diagram, each of which features distinct slopes of the linear relation between superfluid density and the critical temperature. These results are attributed to a possible evolution of the charge order pattern from the superimposed tri-hexagonal Star-of-David phase at low pressures (within the first dome) to the staggered tri-hexagonal phase at intermediate pressures (between the first and second domes). Our findings suggest a change in the nature of the charge-ordered state across the phase diagram of CsV3Sb5, with varying degrees of competition with superconductivity. Kagome metals can house a complex interplay of competing phenomenon and there has been significant investigation into how to engineer the resultant properties, as well as understand the underlying physics. Here, the authors investigate the competition between charge density wave order and superconductivity for CsV3Sb5 using a combination of high-pressure and muon spin rotation measurements. [ABSTRACT FROM AUTHOR]

The recently discovered kagome superconductor CsV3Sb5 (Tc ≃ 2.5 K) has been found to host charge order as well as a non-trivial band topology, encompassing multiple Dirac points and probable surface states. Such a complex and phenomenologically rich system is, therefore, an ideal playground for observing unusual electronic phases. Here, we report anisotropic superconducting properties of CsV3Sb5 by means of transverse-field muon spin rotation (μSR) experiments. The fits of temperature dependences of in-plane and out-of-plane components of the magnetic penetration depth suggest that the superconducting order parameter may have a two-gap (s + s)-wave symmetry. The multiband nature of superconductivity could be further supported by the different temperature dependences of the anisotropic magnetic penetration depth γλ(T) and upper critical field γ B c 2 (T) . The relaxation rates obtained from zero field μSR experiments do not show noticeable change across the superconducting transition, indicating that superconductivity does not break time reversal symmetry. [ABSTRACT FROM AUTHOR]

There is considerable evidence that the superconducting state of Sr2RuO4 breaks time reversal symmetry. In the experiments showing time reversal symmetry breaking, its onset temperature, TTRSB, is generally found to match the critical temperature, Tc, within resolution. In combination with evidence for even parity, this result has led to consideration of a dxz ± idyz order parameter. The degeneracy of the two components of this order parameter is protected by symmetry, yielding TTRSB = Tc, but it has a hard-to-explain horizontal line node at kz = 0. Therefore, s ± id and d ± ig order parameters are also under consideration. These avoid the horizontal line node, but require tuning to obtain TTRSB ≈ Tc. To obtain evidence distinguishing these two possible scenarios (of symmetry-protected versus accidental degeneracy), we employ zero-field muon spin rotation/relaxation to study pure Sr2RuO4 under hydrostatic pressure, and Sr1.98La0.02RuO4 at zero pressure. Both hydrostatic pressure and La substitution alter Tc without lifting the tetragonal lattice symmetry, so if the degeneracy is symmetry-protected, TTRSB should track changes in Tc, while if it is accidental, these transition temperatures should generally separate. We observe TTRSB to track Tc, supporting the hypothesis of dxz ± idyz order. Two possible scenarios of the superconducting order parameter in Sr2RuO4 remain difficult to distinguish. Here, the authors observe that the onset temperature of time reversal symmetry breaking tracks the superconducting transition temperature in Sr2RuO4, supporting a dxz ± idyz order parameter. [ABSTRACT FROM AUTHOR]

Malignant breast tumors are the leading oncological pathology (after skin cancer) in the female population all over the world (more than 20%). According to American Cancer Society, breast cancer is expected to account for 30% of all new cancer cases among women in 2017 (Simon, 2017). The research in the sphere of the timely diagnosis of malignant neoplasms led to the development and further widespread implementation of screening programs, which help to reveal the disease before the onset of symptoms or signs of illness. The paper discusses different scientific approaches to mass screening, various opinions concerning the real impact of screening and contemporary treatment into breast cancer mortality decrease, and presents the results of a breast screening program in the Republic of Tatarstan (Russian Federation). The results showed the effectiveness of this diagnostic method: in 59,000 women aged 50-69 years in total, there were revealed 373 cases of breast cancer (0.63%), in which breast cancer of the I-II stage was 80%. Of the histological forms, 45.4% in the detected malignant neoplasms were presented by invasive ductal cancer, 24.8%—by invasive lobular carcinoma, and the proportion of non-invasive cancer was 4%. Cancer without metastatic involvement of lymphatic nodes (T1-4N0) occurred in 63% of cases. The paper discusses such negative factors of mass mammographic screening as overdiagnosis, false-positive results, and overtreatment. The analyses of existing research all over the world show that since the problem has been actively studied all over the world, the approach to the analysis of screening results has changed to the prevalence of individual approach to each case, the number of cases connected with overdiagnosis is constantly reduced, and the quality of visualization is rapidly improving due to the success of interdisciplinary research and rapid technical progress. [ABSTRACT FROM AUTHOR]

Comparisons of duration of response (DoR) and duration of clinical benefit (DoCB) within clinical trials are prone to biases. To address these biases, we used new methodology to prospectively analyze expected DoR and expected DoCB. Objective response rate and clinical benefit rate were calculated for fulvestrant 500 and 250 mg, and used to calculate expected DoR and expected DoCB for each dose group. The ratios for expected DoR and expected DoCB (expected DoR/expected DoR and expected DoCB/expected DoCB) were then calculated, thereby allowing statistical comparisons of these endpoints between each arm of the COmparisoN of Faslodex In Recurrent or Metastatic breast cancer (CONFIRM) trial. Expected DoRs for fulvestrant 500 and 250 mg were 3.2 and 3.6 months, respectively. The expected DoR ratio between fulvestrant 500 and 250 mg was not statistically significant (0.89; 95 % CI, 0.48-1.67, P = 0.724). The expected DoCBs for fulvestrant 500 and 250 mg were 9.8 and 7.2 months, respectively. The expected DoCB ratio showed that the expected DoCB for fulvestrant 500 mg was significantly improved compared with the expected DoCB for fulvestrant 250 mg (1.36; 95 % CI, 1.07-1.73, P = 0.013). Analysis of the expected DoR and expected DoCB showed fulvestrant 500 mg significantly increased expected DoCB compared with fulvestrant 250 mg in the CONFIRM trial. [ABSTRACT FROM AUTHOR]

In a classical Bardeen–Cooper–Schrieffer superconductor, pairing and coherence of electrons are established simultaneously below the critical transition temperature (Tc), giving rise to a gap in the electronic energy spectrum. In the high-Tc copper oxide superconductors, however, a pseudogap extends above Tc. The relationship between the pseudogap and superconductivity is one of the central issues in this field. Spectral gaps arising from pairing precursors are qualitatively similar to those caused by competing electronic states, rendering a standard approach to their analysis inconclusive. The issue can be settled, however, by studying the correlation between the weights associated with the pseudogap and superconductivity spectral features. Here we report a study of two spectral weights using angle-resolved photoemission spectroscopy. The weight of the superconducting coherent peak increases away from the node following the trend of the superconducting gap, but starts to decrease in the antinodal region. This striking non-monotonicity reveals the presence of a competing state. We demonstrate a direct correlation, for different values of momenta and doping, between the loss in the low-energy spectral weight arising from the opening of the pseudogap and a decrease in the spectral weight associated with superconductivity. We therefore conclude that the pseudogap competes with the superconductivity by depleting the spectral weight available for pairing. [ABSTRACT FROM AUTHOR]

Recently, the transition metal dichalcogenide (TMD) system 2M-WS2 has been identified as a Dirac semimetal exhibiting both superconductivity with the highest Tc ~ 8.5 K among all the TMD materials and topological surface states. Here we report on muon spin rotation (μSR) and density functional theory studies of microscopic SC properties and the electronic structure in 2M-WS2 at ambient and under hydrostatic pressures (pmax = 1.9 GPa). The SC order parameter in 2M-WS2 is determined to have single-gap s-wave symmetry. We further show a strong negative pressure effect on Tc and on the SC gap Δ. This may be partly caused by the pressure induced reduction of the size of the electron pocket around the Γ-point. We also find that the superfluid density ns is weakly affected by pressure. The absence of a strong pressure effect on ns and the absence of a correlation between ns and Tc in 2M-WS2, in contrast to the other SC TMDs Td-MoTe2 and 2H-NbSe2, is explained in terms of its location in the optimal (ambient pressure) and above the optimal (under pressure) superconducting regions of the phase diagram and its large distance to the other possible competing or cooperating orders. [ABSTRACT FROM AUTHOR]

The K2Cr8O16 compound belongs to a series of quasi-1D compounds with intriguing magnetic properties that are stabilized through a high-pressure synthesis technique. In this study, a muon spin rotation, relaxation and resonance (μ+SR) technique is used to investigate the pressure dependent magnetic properties up to 25 kbar. μ+SR allows for measurements in true zero applied field and hereby access the true intrinsic material properties. As a result, a refined temperature/pressure phase diagram is presented revealing a novel low temperature/high pressure (pC1 = 21 kbar) transition from a ferromagnetic insulating to a high-pressure antiferromagnetic insulator. Finally, the current study also indicates the possible presence of a quantum critical point at pC2 ~ 33 kbar where the magnetic order in K2Cr8O16 is expected to be fully suppressed even at T = 0 K. [ABSTRACT FROM AUTHOR]

Similar to chemical doping, pressure produces and stabilizes new phases of known materials, whose properties may differ greatly from those of their standard counterparts. Here, by considering a series of LaFeAs1−xPxO iron-pnictides synthesized under high-pressure high-temperature conditions, we investigate the simultaneous effects of pressure and isoelectronic doping in the 1111 family. Results of numerous macroscopic and microscopic technique measurements unambiguously show a radically different phase diagram for the pressure-grown materials, characterized by the lack of magnetic order and the persistence of superconductivity across the whole 0.3 ≤ x ≤ 0.7 doping range. This unexpected scenario is accompanied by a branching in the electronic properties across x = 0.5, involving both the normal and superconducting phases. Most notably, the superconducting order parameter evolves from nodal (for x < 0.5) to nodeless (for x ≥ 0.5), in clear contrast to other 1111 and 122 iron-based materials grown under ambient-pressure conditions. Superconductivity: Putting the pressure on iron-based superconductors Experiments show how iron-based superconductors synthesized under high pressure differ from those grown under ambient conditions. Iron-based superconductors are an exciting family of materials that exhibit unconventional superconductivity as well as a range of other exotic phases due to a complex interplay between magnetism and superconductivity. Oxypnictides are particularly puzzling members of this family as seemingly similar compounds can exhibit strikingly different electronic properties. By growing and measuring a range of oxypnictide compounds grown under different high-pressure, high-temperature conditions a team of researchers from Switzerland, led by Toni Shiroka from ETH Zürich, show that a close interplay between the magnetism and superconductivity is meditated by spin fluctuations. Furthermore, they show that the superconducting order parameter evolves in a way that is completely opposite to ambient-grown samples. [ABSTRACT FROM AUTHOR]

The recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p 3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p 7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc 1.2 K which decreases upon increasing the pressure. In the intermediate pressure region (3.5 p 7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs. [ABSTRACT FROM AUTHOR]

The kagome metals of the family AV3Sb5, featuring a unique structural motif, harbor an array of intriguing phenomena such as chiral charge order and superconductivity. CsV3Sb5 is of particular interest because it displays a double superconducting dome in the region of the temperature-pressure phase diagram where charge order is still present. However, the microscopic origin of such an unusual behavior remains an unsolved issue. Here, to address it, we combine high-pressure, low-temperature muon spin relaxation/rotation with first-principles calculations. We observe a pressure-induced threefold enhancement of the superfluid density, which also displays a double-peak feature, similar to the superconducting critical temperature. This leads to three distinct regions in the phase diagram, each of which features distinct slopes of the linear relation between superfluid density and the critical temperature. These results are attributed to a possible evolution of the charge order pattern from the superimposed tri-hexagonal Star-of-David phase at low pressures (within the first dome) to the staggered tri-hexagonal phase at intermediate pressures (between the first and second domes). Our findings suggest a change in the nature of the charge-ordered state across the phase diagram of CsV3Sb5, with varying degrees of competition with superconductivity. Kagome metals can house a complex interplay of competing phenomenon and there has been significant investigation into how to engineer the resultant properties, as well as understand the underlying physics. Here, the authors investigate the competition between charge density wave order and superconductivity for CsV3Sb5 using a combination of high-pressure and muon spin rotation measurements. [ABSTRACT FROM AUTHOR]