BUSCADOR RECOLECTA

Ordinary metals contain electron liquids within well-defined ‘Fermi’ surfaces at which the electrons behave as if they were non-interacting. In the absence of transitions to entirely new phases such as insulators or superconductors, interactions between electrons induce scattering that is quadratic in the deviation of the binding energy from the Fermi level. A long-standing puzzle is that certain materials do not fit this ‘Fermi liquid’ description. A common feature is strong interactions between electrons relative to their kinetic energies. One route to this regime is special lattices to reduce the electron kinetic energies. Twisted bilayer graphene is an example, and trihexagonal tiling lattices (triangular ‘kagome’), with all corner sites removed on a 2 × 2 superlattice, can also host narrow electron bands for which interaction effects would be enhanced. Here we describe spectroscopy revealing non-Fermi-liquid behaviour for the ferromagnetic kagome metal Fe3Sn2 (ref. 6). We discover three C3-symmetric electron pockets at the Brillouin zone centre, two of which are expected from density functional theory. The third and most sharply defined band emerges at low temperatures and binding energies by means of fractionalization of one of the other two, most likely on the account of enhanced electron–electron interactions owing to a flat band predicted to lie just above the Fermi level. Our discovery opens the topic of how such many-body physics involving flat bands could differ depending on whether they arise from lattice geometry or from strongly localized atomic orbitals., S.A.E., D.G.-M., H.L., O.V.Y. and M.S. acknowledge the support from NCCR MARVEL funded by the Swiss National Science Foundation (SNSF, grant no. 182892). S.A.E. acknowledges the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 701647. Y.X. acknowledges the National Key Research and Development Program of China (grant no. 2021YFA1600200). S.A.E. and G.A. acknowledge the European Research Council HERO Synergy grant SYG-18 810451. The laser ARPES work at the University of Geneva was supported by the SNSF grants 2000020_165791 and 200020_184998. Part of this work was supported by the High Magnetic Field Laboratory of Anhui Province. Part of this work was performed at the Surfaces/Interfaces: Microscopy (SIM) beamline of the Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland. All first-principles calculations were performed at the Swiss National Supercomputing Centre (CSCS) under the projects s1146 and mr27. Open Access funding provided by Lib4RI – Library for the Research Institutes within the ETH Domain: Eawag, Empa, PSI & WSL.

In this manuscript, we summarise all discussions originated as a result of the WorkStop/ThinkStart 3.0: paving the way to alternative NNLO strategies that took place on 4.-6. November 2019 at the Galileo Galilei Institute for Theoretical Physics (GGI). We gratefully acknowledge the support of GGI and the COST Action CA16201 PARTICLEFACE. We wish to thank toW.M. Marroquin and M. Morandini for their help in organising the workshop. P. Banerjee acknowledges support by the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 701647. A.L. Cherchiglia, B. Hiller and M.Sampaio acknowledge support from Fundacao para a Ciencia e Tecnologia (FCT) through the projects UID/FIS/04564/2020 and CERN/FIS-COM/0035/2019. The work of L. Cieri has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 754496. The work of F. Driencourt-Mangin, G. Rodrigo, G. Sborlini and W.J. Torres Bobadilla is supported by the Spanish Government (Agencia Estatal de Investigacion), ERDF funds from European Commission (Grant No. FPA2017-84445-P), Generalitat Valenciana (Grant No. PROMETEO/2017/053) and from the SpanishGovernment (FJCI-2017-32128). T. Engel acknowledges support by the Swiss National Science Foundation (SNF) under contract 200021_178967. C. Gnendiger, R. Pittau, A. Signer and D. Stockinger wish to thank B. Page for his help in establishing (2.60). The work of R. J. Hernandez-Pinto is supported by CONACyT through the Project No. A1-S-33202 (Ciencia Basica) and Sistema Nacional de Investigadores. G. Pelliccioli was supported by the Bundesministerium fur Bildung und Forschung (BMBF, German Federal Ministry for Education and Research) under contract no. 05H18WWCA1. J. Pires was supported by Fundacao para a Ciencia e Tecnologia (FCT, Portugal) through the contract UIDP/50007/2020 and project CERN/FIS-PAR/0024/2019. The work of R. Pittau has been supported by the SpanishGovernment grant PID2019-106087GB-C21 and by the Junta de Andalucia project P18-FR-4314 (fondos FEDER). M. Sampaio acknowledges a research grant from CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico 303482/2017-6). C. Signorile-Signorile was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Grant no. 396021762 - TRR 257., In this manuscript, we report the outcome of the topical workshop: paving the way to alternative NNLO strategies (https://indico.ific.uv.es/e/WorkStop-ThinkStart_3.0), by presenting a discussion about different frameworks to perform precise higher-order computations for high-energy physics. These approaches implement novel strategies to deal with infrared and ultraviolet singularities in quantum field theories. A special emphasis is devoted to the local cancellation of these singularities, which can enhance the efficiency of computations and lead to discover novel mathematical properties in quantum field theories., European Commission

701647, Portuguese Foundation for Science and Technology

European Commission

UID/FIS/04564/2020
CERN/FIS-COM/0035/2019, European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant

754496, Spanish Government (Agencia Estatal de Investigacion), ERDF funds from European Commission

FPA2017-84445-P, Generalitat Valenciana

European Commission

PROMETEO/2017/053, Spanish Government

European Commission

FJCI-2017-32128
PID2019-106087GB-C21, Swiss National Science Foundation (SNSF)

200021_178967, Consejo Nacional de Ciencia y Tecnologia (CONACyT)

A1-S-33202, Sistema Nacional de Investigadores, Federal Ministry of Education & Research (BMBF)

05H18WWCA1, Portuguese Foundation for Science and Technology

UIDP/50007/2020
CERN/FIS-PAR/0024/2019, Junta de Andalucia

P18-FR-4314, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ)

303482/2017-6, German Research Foundation (DFG)

396021762 - TRR 257, GGI, European Cooperation in Science and Technology (COST)

CA16201 PARTICLEFACE

The design of complex, competing effects in magnetic systems – be it via the introduction of nonlinear interactions, or the patterning of three-dimensional geometries – is an emerging route to achieve new functionalities. Here, we combine 3D geometric effects with non-linear and non-local interactions to produce magnetic field textures in free space. For this, we harness direct write nanofabrication techniques, creating intertwined nanomagnetic cobalt double helices, where curvature, torsion, chirality, and magnetic coupling are jointly exploited. By reconstructing the 3D vectorial magnetic state of the double helices with soft X-ray magnetic laminography, we identify the presence of a regular array of highly coupled locked domain wall pairs in neighbouring helices. Micromagnetic simulations reveal that the magnetisation configuration leads to the formation of an array of complex textures in the magnetic induction, consisting of vortices in the magnetisation and antivortices in free space, which together, form an effective B-field cross-tie wall. The design and creation of complex three-dimensional magnetic field nanotextures opens new possibilities for smart materials, unconventional computing, particle trapping and magnetic imaging., This work was funded by an EPSRC Early Career Fellowship EP/M008517/1 and the Winton Program for the Physics of Sustainability. C.D. acknowledges funding from the Leverhulme Trust (ECF-2018-016), the Isaac Newton Trust (18-08), the L’Oréal-UNESCO UK and Ireland Fellowship For Women In Science 2019, and the Max Planck Society Lise Meitner Excellence Program. A.F.P. acknowledges funding by the European Community under the Horizon 2020 Program, Contract no. 101001290, 3DNANOMAG. A.H.-R. and S.MV. acknowledge the support from European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant ref. H2020-MSCA-IF-2016-746958. A.H.-R. acknowledges funding from Spanish AEI under project reference PID2019–104604RB/AEI/10.13039/501100011033. The PolLux end station was financed by the German Ministerium für Bildung und Forschung (BMBF) through contracts 05K16WED and 05K19WE2. K.W. acknowledges the funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 701647. A.F.P. is grateful to the University of Cambridge and the University of Glasgow, where part of this research was performed., Peer reviewed

We present an improved theoretical prediction of the positron energy spectrum for the polarised Michel decay µ → eνν̄. In addition to the full next-to-next-to-leading order correction of order α in the electromagnetic coupling, we include logarithmically enhanced terms at even higher orders. Logarithms due to collinear emission are included at next-to-leading accuracy up to order α. At the endpoint of the Michel spectrum, soft photon emission results in large logarithms that are resummed up to next-to-next-to-leading logarithmic accuracy. We apply our results in the context of the MEG II and Mu3e experiments to estimate the impact of the theory error on the branching ratio sensitivity for the lepton-flavour-violating decay µ → eX of a muon into an axion-like particle X., Peer reviewed

Heterotrimeric Gα:Gβγ G proteins function as molecular switches downstream of G protein-coupled receptors (GPCRs). They alternate between a heterotrimeric GDP-bound OFF-state and a GTP-bound ON-state in which GαGTP is separated from the Gβγ dimer. Consequently, pharmacological tools to securely prevent the OFF-ON transition are of utmost importance to investigate their molecular switch function, specific contribution to GPCR signal transduction, and potential as drug targets. FR900359 (FR) and YM-254890 (YM), two natural cyclic peptides and highly specific inhibitors of Gq/11 heterotrimers, are exactly such tools. To date, their efficient and long-lasting inhibition of Gq/11 signaling has been attributed solely to a wedge-like binding to Gα, thereby preventing separation of the GTPase and α-helical domains and thus GDP release. Here, we use X-ray crystallography, biochemical and signaling assays, and BRET-based biosensors to show that FR and YM also function as stabilizers of the Gα:Gβγ subunit interface. Our high-resolution structures reveal a network of residues in Gα and two highly conserved amino acids in Gβ that are targeted by FR and YM to glue the Gβγ complex to the inactive GαGDP subunit. Unlike all previously developed nucleotide-state specific inhibitors that sequester Gα in its OFF-state but compete with Gβγ, FR and YM actively promote the inhibitory occlusion of GαGDP by Gβγ. In doing so, they securely lock the entire heterotrimer, not just Gα, in its inactive state. Our results identify FR and YM as molecular glues for Gα and Gβγ that combine simultaneous binding to both subunits with inhibition of G protein signaling., We thank the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project numbers 290827466/FOR2372 (Grants CR464/7-1 to M.C., KO 902/17-2 to G.M.K., 216619161 to G.S., 418513893 to X.D., 290847012 to E.K., and 494832089/GRK2873 to E.K. and L.J.), and the Swiss NSF—Project numbers 192780 (to X.D.) and 183563 (to G.S., under the Sinergia program) for funding. M.J.R. received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Skłodowska-Curie Grant agreement No. 701647. We thank the SLS beamline scientists for their support during crystallography data collection., Peer reviewed

The design of complex, competing effects in magnetic systems-be it via the introduction of nonlinear interactions(1-4), or the patterning of three-dimensional geometriesm-is an emerging route to achieve new functionalities. In particular, through the design of three-dimensional geometries and curvature, intrastructure properties such as anisotropy and chirality, both geometry-induced and intrinsic, can be directly controlled, leading to a host of new physics and functionalities, such as three-dimensional chiral spin states(7), ultrafast chiral domain wall dynamicss(8-10) and spin textures with new spin topologies(7, 11). Here, we advance beyond the control of intrastructure properties in three dimensions and tailor the magnetostatic coupling of neighbouring magnetic structures, an interstructure property that allows us to generate complex textures in the magnetic stray field. For this, we harness direct write nanofabrication techniques, creating intertwined nanomagnetic cobalt double helices, where curvature, torsion, chirality and magnetic coupling are jointly exploited. By reconstructing the three-dimensional vectorial magnetic state of the double helices with soft-X-ray magnetic laminography(12, 13), we identify the presence of a regular array of highly coupled locked domain wall pairs in neighbouring helices. Micromagnetic simulations reveal that the magnetization configuration leads to the formation of an array of complex textures in the magnetic induction, consisting of vortices in the magnetization and antivortices in free space, which together form an effective B field cross-tie wall''s. The design and creation of complex three-dimensional magnetic field nanotextures opens new possibilities for smart materials(15), unconventional computing(2, 16), particle trapping(17, 18) and magnetic imaging(19).