699 research outputs found
Electron Correlation Driven Heavy-Fermion Formation in LiV2O4
Optical reflectivity measurements were performed on a single crystal of the
d-electron heavy-fermion (HF) metal LiV2O4. The results evidence the highly
incoherent character of the charge dynamics for all temperatures above T^*
\approx 20 K. The spectral weight of the optical conductivity is redistributed
over extremely broad energy scales (~ 5 eV) as the quantum coherence of the
charge carriers is recovered. This wide redistribution is, in sharp contrast to
f-electron Kondo lattice HF systems, characteristic of a metallic system close
to a correlation driven insulating state. Our results thus reveal that strong
electronic correlation effects dominate the low-energy charge dynamics and
heavy quasiparticle formation in LiV2O4. We propose the geometrical
frustration, which limits the extension of charge and spin ordering, as an
additional key ingredient of the low-temperature heavy-fermion formation in
this system.Comment: 5 pages, 3 figure
The effect of an imaginary part of the Schwinger-Dyson equation at finite temperature and density
We examined the effect of an imaginary part of the ladder approximation
Schwinger-Dyson equation. We show the imaginary part enhances the effect of the
first order transition, and affects a tricritical point. In particular, a
chemical potential at a tricritical point is moved about 200(MeV). Thus, one
should not ignore the imaginary part. On the other hand, since an imaginary
part is small away from a tricritical point, one should be able to ignore an
imaginary part. In addition, we also examined the contribution of the wave
function renormalization constant.Comment: 12 pages, 14 figure
Observation of Zeeman effect in topological surface state with distinct material dependence
The helical Dirac fermions on the surface of topological insulators host
novel relativistic quantum phenomena in solids. Manipulating spins of
topological surface state (TSS) represents an essential step towards exploring
the theoretically predicted exotic states related to time reversal symmetry
(TRS) breaking via magnetism or magnetic field. Understanding Zeeman effect of
TSS and determining its g-factor are pivotal for such manipulations in the
latter form of TRS breaking. Here, we report those direct experimental
observations in Bi2Se3 and Sb2Te2Se by spectroscopic imaging scanning tunneling
microscopy. The Zeeman shifting of zero mode Landau level is identified
unambiguously by judiciously excluding the extrinsic influences associated with
the non-linearity in the TSS band dispersion and the spatially varying
potential. The g-factors of TSS in Bi2Se3 and Sb2Te2Se are determined to be 18
and -6, respectively. This remarkable material dependence opens a new route to
control the spins in the TSS.Comment: main text: 17 pages, 4 figures; supplementary: 15 pages, 7 figure
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