Abstract
Understanding the competition between superconductivity and other ordered states (such as antiferromagnetic or charge-density-wave (CDW) state) is a central issue in condensed matter ...physics. The recently discovered layered kagome metal
A
V
3
Sb
5
(
A
= K, Rb, and Cs) provides us a new playground to study the interplay of superconductivity and CDW state by involving nontrivial topology of band structures. Here, we conduct high-pressure electrical transport and magnetic susceptibility measurements to study CsV
3
Sb
5
with the highest
T
c
of 2.7 K in
A
V
3
Sb
5
family. While the CDW transition is monotonically suppressed by pressure, superconductivity is enhanced with increasing pressure up to P1 ≈ 0.7 GPa, then an unexpected suppression on superconductivity happens until pressure around 1.1 GPa, after that,
T
c
is enhanced with increasing pressure again. The CDW is completely suppressed at a critical pressure P2 ≈ 2 GPa together with a maximum
T
c
of about 8 K. In contrast to a common dome-like behavior, the pressure-dependent
T
c
shows an unexpected double-peak behavior. The unusual suppression of
T
c
at P1 is concomitant with the rapidly damping of quantum oscillations, sudden enhancement of the residual resistivity and rapid decrease of magnetoresistance. Our discoveries indicate an unusual competition between superconductivity and CDW state in pressurized kagome lattice.
As one of the most fundamental physical phenomena, the anomalous Hall effect (AHE) typically occurs in ferromagnetic materials but is not expected in the conventional superconductors. Here, we have ...observed a giant AHE in kagome superconductor Cs V3 Sb5 with transition temperature (Tc) of 2.7 K. The anomalous Hall conductivity reaches up to 2.1 × 104 Ω–1 cm–1 which is larger than those observed in most of the ferromagnetic metals. Strikingly, the emergence of AHE exactly follows the higher-temperature charge-density-wave (CDW) transition with T CDW ∼ 94 K , indicating a strong correlation between the CDW state and AHE. Furthermore, AHE disappears when the CDW transition is completely suppressed at high pressure. The origin for AHE is attributed to enhanced skew scattering in the CDW state and large Berry curvature arising from the kagome lattice. These discoveries make Cs V3 Sb5 as an ideal platform to study the interplay among nontrivial band topology, CDW, and unconventional superconductivity.
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Molybdenum disulfide attracts additional attention due to its layered structure which allows transformation into a two-dimensional morphology, like graphene. In this paper, three kinds of molybdenum ...disulfides with distinguishable morphologies, i.e.multilayers, a few layers and nanoparticles, are prepared and used as counter electrode materials for dye-sensitized solar cells (DSSCs). The characterization results from X-ray diffraction (XRD) and transmission electron microscopy (TEM) demonstrate that the molybdenum disulfides have an obviously different edge area to basal-plane ratio, with the order: synthesized MoS sub(2) nanoparticles (MoS sub(2)-NPs) > multilayered MoS sub(2) (ML-MoS sub(2)) > few-layered MoS sub(2) (FL-MoS sub(2)). It is interesting that the MoS sub(2) counter electrodes show the same order as above in the energy conversion efficiency measurements of the corresponding DSSCs. Electrochemical impedance spectra (EIS) show that the MoS sub(2)-NPs electrode has the minimum charge-transfer resistance, while the FL-MoS sub(2) electrode provides the maximum. Combined with the results from triiodine ion adsorption experiences and N sub(2)-adsorption measurements, it is proposed that the catalytically active sites of molybdenum disulfide lie on the edges of the typical layered material, but not on the basal planes. In addition, the transparency of the FL-MoS sub(2) electrode is obviously higher than that of the other MoS sub(2) and Pt electrodes.
Due to the strong reactivity of alkaline metals and the easy formation of the impurity phase, the superconducting transition temperature (Tc) of alkaline metals intercalated FeSe is usually limited ...to 45 K. To avoid the formation of impurity and improve the Tc, we intercalate a more chemically inert organic ion (rather than the chemically reactive alkaline metals) into FeSe single crystal in this report. A new FeSe-based superconductor, namely (TBA)0.3FeSe, with Tc of 50 K, is synthesized by intercalating FeSe single crystal with organic ion tetrabutyl ammonium (TBA+) via an electrochemical intercalation method, which has the highest Tc among FeSe-based bulk superconductors. The structure of the organic ion intercalated product consists of the alternate stacking of monolayer FeSe and the organic molecule. The superconductivity of (TBA)0.3FeSe is confirmed by both the magnetic susceptibility and the transport measurement. It is suggested that the chemically inert organic ion should play a key role in the enhancement of Tc by avoiding the formation of impurity and disorder in FeSe plane as possible. We also suggest that the TBA+ intercalated FeSe with well defined shape and higher Tc offer a good playground for further bulk measurement investigation.
A general feature of unconventional superconductors is the existence of a superconducting dome in the phase diagram. Here we report a series of discrete superconducting phases in the simplest ...iron-based superconductor, FeSe thin flakes, by continuously tuning the carrier concentration through the intercalation of Li and Na ions with a solid ionic gating technique. Such discrete superconducting phases are robust against the substitution of 20% S for Se, but they are vulnerable to the substitution of 2% Cu for Fe, highlighting the importance of the iron site being intact. The superconducting phase diagram for FeSe derivatives is given, which is distinct from that of other unconventional superconductors.
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The microstructure of a Ti-8Mo-6Fe ternary alloy with ultrafine grains was systematically studied with Tecnai-G2 F20 field transmission electron microscope and JEMS 2010 transmission electron ...microscope. A new Ti phase with face-centered-cubic (Fm-3m) structure was discovered. The morphology of these FCC Ti phases was elliptical, and they were widely distributed at interfaces between the polygonal BCC TiMoFe phases. The size of the FCC Ti phases was concentrated in the range of 200–450 nm. The lattice constant of FCC Ti phase was 0.431 nm. Simulated high-resolution images of FCC Ti and compounds of FCC TiC, TiN and TiO with different thicknesses and different defocus amounts were carried out to prove that the FCC structure in Ti-8Mo-6Fe alloy was indeed FCC Ti but not FCC TiC, TiN and TiO. First principle calculations revealed the metallic properties and stability of FCC Ti. All alloy elements of Mo and Fe were in the polygonal BCC TiMoFe phases. The semicircular arc periodic strips formed by electron diffuse scattering were present on the selected area electron diffraction (SAED) patterns of the BCC TiMoFe phase, which may come from the ordered domain of Mo and Fe or local ordering by Mo, Fe and Ti.
•The microstructure of a Ti-8Mo-6Fe alloy prepared by powder sintering technology is ultrafine.•FCC (Fm-3m) Ti phase with a lattice constant of 0.431 nm was discovered.•The metallic properties and stability of FCC Ti were revealed by the first principle calculations.•Arc periodic strips formed by electron diffuse scattering were discovered on the SAED patterns of BCC TiMoFe phase.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Objective The incidence of breast cancer related lymphedema (BCRL) varies between 7-35% depending on the combination of treatment modalities. Early detection of BCRL is crucial in order to start an ...effective non-operative treatment program. Because of the lack of prospective research on this topic, this study was undertaken to prospectively determine the effect of Lympho Venous Anastomosis (LVA) on BCRL and to review the current literature. Study design and methods Ten patients who were previously treated for breast cancer by surgery, radiotherapy, and chemotherapy, and were unresponsive to 12-weeks of non-operative treatment, underwent an LVA procedure (Degni-Cordeiro). Objective measurements were gathered for circumferential measurement and water volumetry, and quality of life. Various types of lymphoscintigraphy were carried out pre-operatively and post-operatively at 3 and 12 months. Treatment was embedded in a multidisciplinary setting. Results Post-operative volume measurements initially showed a 4.8% reduction of lymphedema at 3 months and a 2% reduction after one year. Various scintigraphic parameters showed some improvement. Quality of life questionnaires reported minimal improvement. Reviewing the literature, only retrospective studies were found; these reported varying results for LVA procedures. The selection of patients, classification of lymphedema, indications and types of LVA, and additional therapeutic options were heterogeneous, not comparable, and lacked a validated method of effect-assessment. Conclusions Our results showed a minimal reduction in volume of lymphedema following LVA; in the literature, there was no convincing evidence of the success of LVA. Non-operative treatment and elastic stockings are still preferred by most patients with lymphedema, especially in early stages with few irreversible changes.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Intercritical tempering at 680°C for different times was carried out in a low carbon copper-bearing steel to study the evolution of the crystal structure of Cu precipitates by high resolution ...transmission electron microscopy. With increased tempering time, four different types of crystal structure of copper precipitates with different sizes were observed, namely, (a) nano-ordered clusters comprised of B2 FeCu nano-ordered clusters (2–3nm) and weak ordered BCC Cu nanoclusters (2–3nm), (b) 9R Cu (5–12nm) - multiple twinned structure consisted of two, six or seven 9R twins with an orientation relationship of (1 1–4)9R∥(0 1 1)α, −1 1 09R∥1 −1 1α, (c) detwinned 9R Cu (24–26nm) consisted of two 9R parts and a removable interface (1 1–4)9R, and (d) FCC Cu (~37nm) precipitates consisted of two parts of FCC Cu and a micro-twinned region. The evolution sequence of crystal structure of Cu precipitates was: nano-ordered clusters→9R Cu→detwinned 9R Cu→FCC Cu. The maximum contribution to precipitation hardening is attributed to nano-ordered clusters.
Heat treatment process of experimental steel, hardness data of experimental steel, evolution sequence of crystal structure of Cu precipitation, and schematic of evolution process of Cu precipitation. Display omitted
•B2-FeCu nano-ordered clusters exist in the studied steel.•The detwinned process of 9R-Cu has been revealed.•The crystal structure sequence of Cu precipitation with different time of intercritical tempering has been identified.•The maximum contribution to precipitation hardening is attributed to nano-ordered clusters.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The importance of the spin-orbit coupling (SOC) effect in Fe-based superconductors (FeSCs) has recently been under hot debate. Considering the Hund’s coupling-induced electronic correlation, the ...understanding of the role of SOC in FeSCs is not trivial and is still elusive. Here, through a comprehensive study ofSe77andFe57nuclear magnetic resonance, a nontrivial SOC effect is revealed in the nematic state of FeSe. First, the orbital-dependent spin susceptibility, determined by the anisotropy of theFe57Knight shift, indicates a predominant role from the3dxyorbital, which suggests the coexistence of local and itinerant spin degrees of freedom in the FeSe. Then, we reconfirm that the orbital reconstruction below the nematic transition temperature (Tnem∼90K) happens not only on the3dxzand3dyzorbitals but also on the3dxyorbital, which is beyond a trivial ferro-orbital order picture. Moreover, our results also indicate the development of a coherent coupling between the local and itinerant spin degrees of freedom belowTnem, which is ascribed to a Hund’s coupling-induced electronic crossover on the3dxyorbital. Finally, because of a nontrivial SOC effect, sizable in-plane anisotropy of the spin susceptibility emerges in the nematic state, suggesting a spin-orbital-intertwined nematicity rather than a simple spin- or orbital-driven nematicity. The present work not only reveals a nontrivial SOC effect in the nematic state but also sheds light on the mechanism of nematic transition in FeSe.
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