292 research outputs found
Temperature independent band structure of WTe2 as observed from ARPES
Extremely large magnetoresistance (XMR), observed in transition metal
dichalcogendies, WTe, has attracted recently a great deal of research
interests as it shows no sign of saturation up to the magnetic field as high as
60 T, in addition to the presence of type-II Weyl fermions. Currently, there
has been a lot of discussion on the role of band structure changes on the
temperature dependent XMR in this compound. In this contribution, we study the
band structure of WTe using angle-resolved photoemission spectroscopy
(ARPES) and first-principle calculations to demonstrate that the temperature
dependent band structure has no substantial effect on the temperature dependent
XMR as our measurements do not show band structure changes on increasing the
sample temperature between 20 and 130 K. We further observe an electronlike
surface state, dispersing in such a way that it connects the top of bulk
holelike band to the bottom of bulk electronlike band. Interestingly, similar
to bulk states, the surface state is also mostly intact with the sample
temperature. Our results provide invaluable information in shaping the
mechanism of temperature dependent XMR in WTe.Comment: 7 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1705.0721
Evidence of momentum dependent hybridization in Ce2Co0.8Si3.2
We studied the electronic structure of the Kondo lattice system Ce2Co0.8Si3.2
by angle-resolved photoemission spectroscopy (ARPES). The spectra obtained
below the coherence temperature consist of a Kondo resonance, its spin-orbit
partner and a number of dispersing bands. The quasiparticle weight related to
the Kondo peak depends strongly on Fermi vectors associated with bulk bands.
This indicates a highly anisotropic hybridization between conduction band and
4f electrons - V_{cf} in Ce2Co0.8Si3.2.Comment: 6 page
Transfer of spectral weight across the gap of Sr2IrO4 induced by La doping
We study with Angle Resolved PhotoElectron Spectroscopy (ARPES) the evolution
of the electronic structure of Sr2IrO4, when holes or electrons are introduced,
through Rh or La substitutions. At low dopings, the added carriers occupy the
first available states, at bottom or top of the gap, revealing an anisotropic
gap of 0.7eV in good agreement with STM measurements. At further doping, we
observe a reduction of the gap and a transfer of spectral weight across the
gap, although the quasiparticle weight remains very small. We discuss the
origin of the in-gap spectral weight as a local distribution of gap values
Spin- and angle-resolved photoemission studies of the electronic structure of Si(110)"16x2" surfaces
The electronic structure of Si(110)"16 x 2" double-domain, single-domain and
1 x 1 surfaces have been investigated using spin- and angle-resolved
photoemission at sample temperatures of 77 K and 300 K. Angle-resolved
photoemission was conducted using horizontally- and vertically-polarised 60 eV
and 80 eV photons. Band-dispersion maps revealed four surface states ( to
) which were assigned to silicon dangling bonds on the basis of measured
binding energies and photoemission intensity changes between horizontal and
vertical light polarisations. Three surface states (, and ),
observed in the Si(110)"16 x 2" reconstruction, were assigned to Si adatoms and
Si atoms present at the edges of the corrugated terrace structure. Only one of
the four surface states, , was observed in both the Si(110)"16 x 2" and 1
x 1 band maps and consequently attributed to the pervasive Si zigzag chains
that are components of both the Si(110)"16 x 2" and 1 x 1 surfaces. A state in
the bulk-band region was attributed to an in-plane bond. All data were
consistent with the adatom-buckling model of the Si(110)"16 x 2" surface.
Whilst room temperature measurements of and were statistically
compatible with zero, measurements of the enantiomorphic A-type and
B-type Si(110)"16 x 2" surfaces gave small average polarisations of around
1.5\% that were opposite in sign. Further measurements at 77 K on A-type
Si(110)"16 x 2" surface gave a smaller value of +0.3\%. An upper limit of
may thus be taken for the longitudinal polarisation.Comment: Main paper: 12 pages and 11 figures. Supplemental information: 5
pages and 2 figure
Promjene spektralnih svojstava kuprata visokog Tc izazvane defektima
Superconductivity in high-Tc cuprates is particularly sensitive to disorder due to the unconventional d-wave pairing symmetry. We investigated effects of disorder on the spectral properties of Bi2Sr2CaCu2O8+x high-Tc superconductor. We found that already small defect densities suppress the characteristic spectral signature of the superconducting state. The spectral line shape clearly reflects new excitations within the gap, as expected for defect-induced pair breaking. At the lowest defect concentrations the normal state remains unaffected, while increased disorder leads to suppression of the normal quasiparticle peaks.Zbog nekonvencionalne d-valne simetrije, supravodljivost u visokotemperaturnim kupratima je posebno osjetljiva na neuređenost. Ispitivali smo utjecaj neuređenosti na spektralna svojstva Bi2Sr2CaCu2O8+x supravodiča primjenom ARPES metode. Već mala gustoća defekata smanjuje karakteristični spektralni odziv supravodljivog stanja. Oblik spektralne linije očito reflektira nova pobuđenja unutar zabranjene vrpce, kako se i očekuje u slučaju razbijanja Cooperovih parova izazvanog defektima. Za male koncentracije defekata, normalno stanje ostaje nepromijenjeno, dok viši stupanj neuređenosti smanjuje intenzitet spektralnih linija kvazičestica
- …