436 research outputs found
Coexistence of localized and itinerant electrons in BaFe2X3 (X = S and Se) revealed by photoemission spectroscopy
We report a photoemission study at room temperature on BaFe2X3 (X = S and Se)
and CsFe2Se3 in which two-leg ladders are formed by the Fe sites. The Fe 2p
core-level peaks of BaFe2X3 are broad and exhibit two components, indicating
that itinerant and localized Fe 3d sites coexist similar to KxFe2-ySe2. The Fe
2p core-level peak of CsFe2Se3 is rather sharp and is accompanied by a
charge-transfer satellite. The insulating ground state of CsFe2Se3 can be
viewed as a Fe2+ Mott insulator in spite of the formal valence of +2.5. The
itinerant versus localized behaviors can be associated with the stability of
chalcogen p holes in the two-leg ladder structure.Comment: 5 pages, 5 figures, Accepted in publication for Physical Review
Orbital-dependent modifications of electronic structure across magneto-structural transition in BaFe2As2
Laser angle-resolved photoemission spectroscopy (ARPES) is employed to
investigate the temperature (T) dependence of the electronic structure in
BaFe2As2 across the magneto-structural transition at TN ~ 140 K. A drastic
transformation in Fermi surface (FS) shape across TN is observed, as expected
by first-principles band calculations. Polarization-dependent ARPES and band
calculations consistently indicate that the observed FSs at kz ~ pi in the
low-T antiferromagnetic (AF) state are dominated by the Fe3dzx orbital, leading
to the two-fold electronic structure. These results indicate that
magneto-structural transition in BaFe2As2 accompanies orbital-dependent
modifications in the electronic structure.Comment: 13 pages, 4 figures. accepted by Physical Review Letter
Observation of Giant Band Splitting in Altermagnetic MnTe
We performed angle-resolved photoemission spectroscopy (ARPES) on hexagonal
MnTe, a candidate for an altermagnet with a high critical temperature
(TN=307K). By utilizing photon-energy-tunable ARPES in combination with
first-principles calculations, we found that the band structure in the
antiferromagnetic phase exhibits a strongly anisotropic band-splitting
associated with the time-reversal-symmetry breaking, providing the first direct
experimental evidence for the altermagnetic band-splitting. The magnitude of
the splitting reaches 0.8 eV at non-high-symmetry momentum points, which is
much larger than the spin-orbit gap of ~0.3 eV along the GammaK high-symmetry
cut. The present result paves the pathway toward realizing exotic physical
properties associated with the altermagnetic spin-splitting.Comment: 17 pages, 6 figure
Anomalous Hall effect as a probe of the chiral order in spin glasses
Anomalous Hall effect arising from the noncoplanar spin configuration
(chirality) is discussed as a probe of the chiral order in spin glasses. It is
shown that the Hall coefficient yields direct information about the linear and
nonlinear chiral susceptibilities of the spin sector, which has been hard to
obtain experimentally from the standard magnetic measurements. Based on the
chirality scenario of spin-glass transition, predictions are given on the
behavior of the Hall resistivity of canonical spin glasses.Comment: Order estimate of the effect given, one reference added. To appear in
Phys. Rev. Letter
Gallinitiation enhances the availability of food resources for herbivorous insects
Summary 1. Insect herbivory may have not only negative but also positive plant-mediated effects on other insect herbivores. We investigated plant-mediated effects of the stem gall midge Rabdophaga rigidae on other insect herbivores through regrowth response of the willow Salix eriocarpa. 2. Gall initiation on current-year shoots stimulated the development of lateral shoots, followed by a secondary leaf flush. Lateral shoots and upper leaves on galled shoots were less tough and had a higher water and nitrogen content. 3. Colonization rates by the aphid Aphis farinosa were significantly higher on galled shoots than on ungalled shoots, because this aphid frequently colonized lateral shoots. 4. Adults of two leaf beetles, Plagiodera versicolora and Smaragdina semiaurantiaca , were more abundant on galled than on ungalled shoots; they preferentially fed on young leaves produced during the secondary leaf flush. 5. Gall initiation positively affected aphids and leaf beetles by enhancing the availability of food resources as a result of the regrowth responses of S. eriocarpa . This indicates that the regrowth responses of plants to insect herbivory provide an important mechanism responsible for positive effects on other insect herbivores
- …