54 research outputs found
Anomalously enhanced photoemission from the Dirac point and symmetry of the self-energy variations for the surface states in Bi2Se3
Accurate analysis of the photoemission intensity from the surface states of
Bi2Se3 reveals two unusual features: spectral line asymmetry and anomalously
enhanced photoemission from the Dirac point. The former indicates a certain
symmetry of a scattering process, which results in strongly k\omega-dependent
contribution to the imaginary part of the self-energy that changes sign while
crossing both the dispersion curves and the energy of the Dirac point. The
latter is hard to describe by one particle spectral function while a final
state interference seems to be plausible explanation
Photoemission induced gating of topological insulator
The recently discovered topological insulators exhibit topologically
protected metallic surface states which are interesting from the fundamental
point of view and could be useful for various applications if an appropriate
electronic gating can be realized. Our photoemission study of Cu intercalated
Bi2Se3 shows that the surface states occupancy in this material can be tuned by
changing the photon energy and understood as a photoemission induced gating
effect. Our finding provides an effective tool to investigate the new physics
coming from the topological surface states and suggests the intercalation as a
recipe for synthesis of the material suitable for electronic applications.Comment: + resistivity data and some discussio
A weak-coupling superconductivity in the electron doped NaFeCoAs is revealed by ARPES
We report a systematic study on the electronic structure and superconducting
(SC) gaps in electron doped NaFeCoAs superconductor using
angle-resolved photoemission spectroscopy. Hole-like Fermi sheets are at the
zone center and electron-like Fermi sheets are at the zone corner, and are
mainly contributed by and orbital characters. Our results reveal a
in the range of 1.8-2.1, suggesting a weak-coupling
superconductivity in these compounds. Gap closing above the transition
temperature () shows the absence of pseudogaps. Gap evolution with
temperature follow the BCS gap equation near the , , and high
symmetry points. Furthermore, an almost isotropic superconductivity along
direction in the momentum space is observed by varying the excitation energies.Comment: 6 pages, 5 figures, Accepted by Phy.Rev.
Exotic Kondo crossover in a wide temperature region in the topological Kondo insulator SmB6 revealed by high-resolution ARPES
Temperature dependence of the electronic structure of SmB6 is studied by
high-resolution ARPES down to 1 K. We demonstrate that there is no essential
difference for the dispersions of the surface states below and above the
resistivity saturating anomaly (~ 3.5 K). Quantitative analyses of the surface
states indicate that the quasi-particle scattering rate increases linearly as a
function of temperature and binding energy, which differs from Fermi-Liquid
behavior. Most intriguingly, we observe that the hybridization between the d
and f states builds gradually over a wide temperature region (30 K < T < 110
K). The surface states appear when the hybridization starts to develop. Our
detailed temperature-dependence results give a complete interpretation of the
exotic resistivity result of SmB6, as well as the discrepancies among
experimental results concerning the temperature regions in which the
topological surface states emerge and the Kondo gap opens, and give new
insights into the exotic Kondo crossover and its relationship with the
topological surface states in the topological Kondo insulator SmB6.Comment: 8 pages, 5 figure
Time of life as it is in LiFeAs
The time of life of fermionic quasiparticles, the distribution of which in
the momentum-energy space can be measured by angle resolved photoemission
(ARPES), is the first quantity to look for fingerprints of interaction
responsible for the superconducting pairing. Such an approach has been recently
used for superconducting cuprates, but its direct application to pnictides was
not possible due to essential three-dimensionality of the electronic band
structure and magnetic ordering. Here, we report the investigation of the
quasiparticle lifetime in LiFeAs, a non-magnetic stoichiometric superconductor
with a well separated two-dimensional band. We have found two energy scales:
the lower one contains clear fingerprints of optical phonon modes while the
higher scale indicates a presence of strong electron-electron interaction. The
result suggests that LiFeAs is a phonon mediated superconductor with strongly
enhanced electronic density of states at the Fermi level.Comment: reevaluated electron-phonon coupling strength, added reference
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