The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, characterized by Cooper pairs condensed at finite momentum, has been a long-sought state that remains unresolved in many classes of fermionic ...systems, including superconductors and ultracold atoms. A fascinating aspect of the FFLO state is the emergence of periodic nodal planes in real space, but its observation is still lacking. Here we investigate the superconducting order parameter at high magnetic fields H applied perpendicular to the ab plane in a high-purity single crystal of FeSe. The heat capacity and magnetic torque provide thermodynamic evidence for a distinct superconducting phase at the low-temperature/high-field corner of the phase diagram. Despite the bulk superconductivity, spectroscopic-imaging scanning tunneling microscopy performed on the same crystal demonstrates that the order parameter vanishes at the surface upon entering the high-field phase. These results provide the first demonstration of a pinned planar node perpendicular to H, which is consistent with a putative FFLO state.
The plasma membrane, the outermost surface of eukaryotic cells, contains various substructures, such as protrusions or invaginations, which are associated with diverse functions, including ...endocytosis and cell migration. These structures of the plasma membrane can be considered as tubules or inverted tubules (protrusions) of the membrane. There are six modes of membrane curvature at the plasma membrane, which are classified by the positive or negative curvature and the location of the curvature (tip, neck or shaft of the tubules). The BAR domain superfamily proteins have structurally determined positive and negative curvatures of membrane contact at their BAR, F-BAR and I-BAR domains, which generate and maintain such curved membranes by binding to the membrane. Importantly, the SH3 domains of the BAR domain superfamily proteins bind to the actin regulatory WASP/WAVE proteins, and the BAR/F-BAR/I-BAR domain-SH3 unit could orient the actin filaments towards the membrane for each subcellular structure. These membrane tubulations are also considered to function in membrane fusion and fission.
The two-dimensional spin-1/2 kagome Heisenberg antiferromagnet is believed to host quantum spin liquid (QSL) states with no magnetic order, but its ground state remains largely elusive. An important ...outstanding question concerns the presence or absence of the 1/9 magnetization plateau, where exotic quantum states, including topological ones, are expected to emerge. Here we report the magnetization of a recently discovered kagome QSL candidate YCu_{3}(OH)_{6.5}Br_{2.5} up to 57 T. Above 50 T, a clear magnetization plateau at 1/3 of the saturation moment of Cu^{2+} ions is observed, supporting that this material provides an ideal platform for the kagome Heisenberg antiferromagnet. Remarkably, we found another magnetization plateau around 20 T, which is attributed to the 1/9 plateau. The temperature dependence of this plateau reveals the presence of the spin gap. The observation of 1/9 and 1/3 plateaus highlights the emergence of novel states in quantum spin systems.The two-dimensional spin-1/2 kagome Heisenberg antiferromagnet is believed to host quantum spin liquid (QSL) states with no magnetic order, but its ground state remains largely elusive. An important outstanding question concerns the presence or absence of the 1/9 magnetization plateau, where exotic quantum states, including topological ones, are expected to emerge. Here we report the magnetization of a recently discovered kagome QSL candidate YCu_{3}(OH)_{6.5}Br_{2.5} up to 57 T. Above 50 T, a clear magnetization plateau at 1/3 of the saturation moment of Cu^{2+} ions is observed, supporting that this material provides an ideal platform for the kagome Heisenberg antiferromagnet. Remarkably, we found another magnetization plateau around 20 T, which is attributed to the 1/9 plateau. The temperature dependence of this plateau reveals the presence of the spin gap. The observation of 1/9 and 1/3 plateaus highlights the emergence of novel states in quantum spin systems.
Abstract
Kondo lattice materials, where localized magnetic moments couple to itinerant electrons, provide a very rich backdrop for strong electron correlations. They are known to realize many exotic ...phenomena, with a dramatic example being recent observations of quantum oscillations and metallic thermal conduction in insulators, implying the emergence of enigmatic charge-neutral fermions. Here, we show that thermal conductivity and specific heat measurements in insulating YbIr
3
Si
7
reveal emergent neutral excitations, whose properties are sensitively changed by a field-driven transition between two antiferromagnetic phases. In the low-field phase, a significant violation of the Wiedemann-Franz law demonstrates that YbIr
3
Si
7
is a charge insulator but a thermal metal. In the high-field phase, thermal conductivity exhibits a sharp drop below 300 mK, indicating a transition from a thermal metal into an insulator/semimetal driven by the magnetic transition. These results suggest that spin degrees of freedom directly couple to the neutral fermions, whose emergent Fermi surface undergoes a field-driven instability at low temperatures.
Neural Wiskott-Aldrich syndrome protein (N-WASP) functions
in several intracellular events including filopodium formation,
vesicle transport and movement of Shigella frexneri and vaccinia virus, by ...stimulating rapid actin
polymerization through the Arp2/3 complex. N-WASP is regulated by the direct
binding of Cdc42 (refs 7, 8
), which exposes the domain in N-WASP that activates the Arp2/3
complex. A WASP-related protein, WAVE/Scar, functions in
Rac-induced membrane ruffling; however, Rac does not bind
directly to WAVE, raising the question of how WAVE is regulated
by Rac. Here we demonstrate that IRSp53, a substrate for insulin receptor with unknown function, is the ‘missing link’ between
Rac and WAVE. Activated Rac binds to the amino terminus of IRSp53, and carboxy-terminal
Src-homology-3 domain of IRSp53 binds to WAVE to form a trimolecular complex.
From studies of ectopic expression, we found that IRSp53 is essential for
Rac to induce membrane ruffling, probably because it recruits WAVE, which
stimulates actin polymerization mediated by the Arp2/3 complex.
A series of Al-5 wt pct Si alloys with Yb additions (up to 6100 ppm) have been investigated using thermal analysis and multiscale microstructure characterization techniques. The addition of Yb was ...found to cause no modification effect to a fibrous morphology involving Si twinning; however, a refined plate-like eutectic structure was observed. The Al
2
Si
2
Yb phase was observed with Yb addition level of more than 1000 ppm. Within the eutectic Al and Si phases, the Al
2
Si
2
Yb phase was also found as a precipitation from the remained liquid. No Yb was detected in the α-Al matrix or plate-like Si particle, even with Yb addition up to 6100 ppm. The absence of Yb inside the eutectic Si particle may partly explain why no significant Si twinning was observed along {111}
Si
planes in the eutectic Si particle. In addition, the formation of the thermodynamic stable YbP phases is also proposed to deteriorate the potency of AlP phase in Al alloys. This investigation highlights to distinguish the modification associated with the ever present P in Al alloys. We define modification as a transition from faceted to fibrous morphology, while a reduction of the Si size is termed refinement.
Profilin was first identified as an actin monomer binding protein; however, recent reports indicate its involvement in actin polymerization. To date, there is no direct evidence of a functional role ...in vivo for profilin in actin cytoskeletal reorganization. Here, we prepared a profilin mutant (H119E) defective in actin binding, but retaining the ability to bind to other proteins. This mutant profilin I suppresses actin polymerization in microspike formation induced by N‐WASP, the essential factor in microspike formation. Profilin associates both in vivo and in vitro with N‐WASP at proline‐rich sites different from those to which Ash/Grb2 binds. This association between profilin and N‐WASP is required for N‐WASP‐induced efficient microspike elongation. Moreover, we succeeded in reconstituting microspike formation in permeabilized cells using profilin I combined with N‐WASP and its regulator, Cdc42. These findings provide the first evidence that profilin is a key molecule linking a signaling network to rapid actin polymerization in microspike formation.
Novel topological phenomena are anticipated for three-dimensional (3D) Dirac electrons. The magnetotransport properties of cubic Sr3PbO antiperovskite, theoretically proposed to be a 3D massive Dirac ...electron system, are studied. The measurements of Shubnikov–de Haas oscillations and Hall resistivity indicate the presence of a low density (∼1×1018cm−3) of holes with an extremely small cyclotron mass of 0.01–0.06me. The magnetoresistance Δρxx(B) is linear in magnetic field B with the magnitude independent of temperature. These results are fully consistent with the presence of 3D massive Dirac electrons in Sr3PbO. The chemical flexibility of the antiperovskites and our findings in the family member Sr3PbO point to their potential as a model system in which to explore exotic topological phases.
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