51 research outputs found
Electron correlations in MnGaAs as seen by resonant electron spectroscopy and dynamical mean field theory
After two decades from the discovery of ferromagnetism in Mn-doped GaAs, its
origin is still debated, and many doubts are related to the electronic
structure. Here we report an experimental and theoretical study of the valence
electron spectrum of Mn-doped GaAs. The experimental data are obtained through
the differences between off- and on-resonance photo-emission data. The
theoretical spectrum is calculated by means of a combination of
density-functional theory in the local density approximation and dynamical
mean-field theory (LDA+DMFT), using exact diagonalisation as impurity solver.
Theory is found to accurately reproduce measured data, and illustrates the
importance of correlation effects. Our results demonstrate that the Mn states
extend over a broad range of energy, including the top of the valence band, and
that no impurity band splits off from the valence band edge, while the induced
holes seem located primarily around the Mn impurity.Comment: 5 pages, 4 figure
Charge self-consistent dynamical mean-field theory based on the full-potential linear muffin-tin orbital method: methodology and applications
Full charge self-consistence (CSC) over the electron density has been
implemented into the local density approximation plus dynamical mean-field
theory (LDA+DMFT) scheme based on a full-potential linear muffin-tin orbital
method (FP-LMTO). Computational details on the construction of the electron
density from the density matrix are provided. The method is tested on the
prototypical charge-transfer insulator NiO using a simple static Hartree-Fock
approximation as impurity solver. The spectral and ground state properties of
bcc Fe are then addressed, by means of the spin-polarized T-matrix fluctuation
exchange solver (SPTF). Finally the permanent magnet SmCo is studied using
multiple impurity solvers, SPTF and Hubbard I, as the strength of the local
Coulomb interaction on the Sm and Co sites are drastically different. The
developed CSC-DMFT method is shown to in general improve on materials
properties like magnetic moments, electronic structure and the materials
density.Comment: 10 pages, 5 figure
High photon energy spectroscopy of NiO: experiment and theory
We have revisited the valence band electronic structure of NiO by means of
hard x-ray photoemission spectroscopy (HAXPES) together with theoretical
calculations using both the GW method and the local density approximation +
dynamical mean-field theory (LDA+DMFT) approaches. The effective impurity
problem in DMFT is solved through the exact diagonalization (ED) method. We
show that the LDA+DMFT method alone cannot explain all the observed structures
in the HAXPES spectra. GW corrections are required for the O bands and Ni-s and
p derived states to properly position their binding energies. Our results
establish that a combination of the GW and DMFT methods is necessary for
correctly describing the electronic structure of NiO in a proper ab-initio
framework. We also demonstrate that the inclusion of photoionization cross
section is crucial to interpret the HAXPES spectra of NiO.We argue that our
conclusions are general and that the here suggested approach is appropriate for
any complex transition metal oxide.Comment: 16 pages, 5 figure
Identifying the electronic character and role of the Mn states in the valence band of (Ga,Mn)As
We report high-resolution hard x-ray photoemission spectroscopy results on
(Ga,Mn)As films as a function of Mn doping. Supported by theoretical
calculations we identify, over the entire 1% to 13% Mn doping range, the
electronic character of the states near the top of the valence band.
Magnetization and temperature dependent core-level photoemission spectra reveal
how the delocalized character of the Mn states enables the bulk ferromagnetic
properties of (Ga,Mn)As.Comment: prl submitte
“Money's too tight (to mention)”:A review and psychological synthesis of living wage research
Traditional living wage research has been the purview of economists, but recently contributions from the field of work psychology have challenged existing perspectives, providing a different lens through which to consider this issue. By means of a narrative interdisciplinary review of 115 peer-reviewed journal articles published between 2000 and 2020, we chart the transitions in the field with attention shifting from macro-economic and econometric lens largely concerned with the costs of living wage policies, to a more person-centric lens focusing on the employee and their family. Synthesizing prior study, we outline five key themes: consequences for individuals, organizations, and societies; changes in operationalization; exploration of different contexts; study of social movements; and the history of the topic. We outline the importance of work psychology in developing the living wage debate through more inclusive definitions, and novel operationalization and measurement, thereby providing fresh insights into how and why living wages can have a positive impact. Critically, we outline the redundancy of simple study of wage rates without understanding the elements that make work decent. We raise key areas for further study, and this topic presents a significant opportunity for psychology to shift focus to impact upstream policy by providing new empirical evidence, and challenges to structural inequalities
Uncovering the multifaceted roles played by neutrophils in allogeneic hematopoietic stem cell transplantation
Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a life-saving procedure used for the treatment of selected hematological malignancies, inborn errors of metabolism, and bone marrow failures. The role of neutrophils in alloHSCT has been traditionally evaluated only in the context of their ability to act as a first line of defense against infection. However, recent evidence has highlighted neutrophils as key effectors of innate and adaptive immune responses through a wide array of newly discovered functions. Accordingly, neutrophils are emerging as highly versatile cells that are able to acquire different, often opposite, functional capacities depending on the microenvironment and their differentiation status. Herein, we review the current knowledge on the multiple functions that neutrophils exhibit through the different stages of alloHSCT, from the hematopoietic stem cell (HSC) mobilization in the donor to the immunological reconstitution that occurs in the recipient following HSC infusion. We also discuss the influence exerted on neutrophils by the immunosuppressive drugs delivered in the course of alloHSCT as part of graft-versus-host disease (GVHD) prophylaxis. Finally, the potential involvement of neutrophils in alloHSCT-related complications, such as transplant-associated thrombotic microangiopathy (TA-TMA), acute and chronic GVHD, and cytomegalovirus (CMV) reactivation, is also discussed. Based on the data reviewed herein, the role played by neutrophils in alloHSCT is far greater than a simple antimicrobial role. However, much remains to be investigated in terms of the potential functions that neutrophils might exert during a highly complex procedure such as alloHSCT
A randomized controlled trial of an intervention for infants’ behavioral sleep problems
Ultrafast modification of the electronic structure of a correlated insulator
A nontrivial balance between Coulomb repulsion and kinematic effects determines the electronic structure of correlated electron materials. The use of electromagnetic fields strong enough to rival these native microscopic interactions allows us to study the electronic response as well as the time scales and energies involved in using quantum effects for possible applications. We use element specific transient x ray absorption spectroscopy and high harmonic generation to measure the response to ultrashort off resonant optical fields in the prototypical correlated electron insulator NiO. Surprisingly, fields of up to 0.22 V lead to no detectable changes in the correlated Ni 3d orbitals contrary to previous predictions. A transient directional charge transfer is uncovered, a behavior that is captured by first principles theory. Our results highlight the importance of retardation effects in electronic screening and pinpoints a key challenge in functionalizing correlated materials for ultrafast device operatio
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