37 research outputs found
Effect of the sample work function on alkali metal dosing induced electronic structure change
Alkali metal dosing (AMD) has been widely used as a way to control doping
without chemical substitution. This technique, in combination with angle
resolved photoemission spectroscopy (ARPES), often provides an opportunity to
observe unexpected phenomena. However, the amount of transferred charge and the
corresponding change in the electronic structure vary significantly depending
on the material. Here, we report study on the correlation between the sample
work function and alkali metal induced electronic structure change for three
iron-based superconductors: FeSe, Ba(FeCo)As and
NaFeAs which share a similar Fermi surface topology. Electronic structure
change upon monolayer of alkali metal dosing and the sample work function were
measured by ARPES. Our results show that the degree of electronic structure
change is proportional to the difference between the work function of the
sample and Mulliken's absolute electronegativity of the dosed alkali metal.
This finding provides a possible way to estimate the AMD induced electronic
structure change.Comment: 4 page
Surface electronic structure of the topological Kondo insulator candidate correlated electron system SmB6
The Kondo insulator SmB6 has long been known to exhibit low temperature
transport anomalies whose origin is of great interest. Here we uniquely access
the surface electronic structure of the anomalous transport regime by combining
state-of-the-art laser- and synchrotron-based angle-resolved photoemission
techniques. We observe clear in-gap states (up to 4 meV), whose temperature
dependence is contingent upon the Kondo gap formation. In addition, our
observed in-gap Fermi surface oddness tied with the Kramers' points topology,
their coexistence with the two-dimensional transport anomaly in the Kondo
hybridization regime, as well as their robustness against thermal recycling,
taken together, collectively provide by-far the strongest evidence for
protected surface metallicity with a Fermi surface whose topology is consistent
with the theoretically predicted topological surface Fermi surface (TSS). Our
observations of systematic surface electronic structure provide the fundamental
electronic parameters for the anomalous Kondo ground state of the correlated
electron material SmB6.Comment: Nature Commun., in press (17 pages, 4 Figs), see related papers at
http://arxiv.org/abs/1306.4634 and
http://scholar.google.com/citations?user=G1Qpy6MAAAAJ&hl=e
X-ray magnetic circular dichroism and photoemission study of the diluted ferromagnetic semiconductor ZnCrTe
We have performed x-ray magnetic circular dichroism (XMCD) and valence-band
photoemission studies of the diluted ferromagnetic semiconductor
ZnCrTe. XMCD signals due to ferromagnetism were observed at the Cr
2p absorption edge. Comparison with atomic multiplet calculations suggests that
the magnetically active component of the Cr ion was divalent under the
tetrahedral crystal field with tetragonal distortion along the crystalline a-,
b-, and c-axes. In the valence-band spectra, spectral weight near the Fermi
level was strongly suppressed, suggesting the importance of Jahn-Teller effect
and the strong Coulomb interaction between the Cr 3d electrons