1,064 research outputs found
X-ray induced electronic structure change in CuIrS
The electronic structure of CuIrS has been investigated using various
bulk-sensitive x-ray spectroscopic methods near the Ir -edge: resonant
inelastic x-ray scattering (RIXS), x-ray absorption spectroscopy in the partial
fluorescence yield (PFY-XAS) mode, and resonant x-ray emission spectroscopy
(RXES). A strong RIXS signal (0.75 eV) resulting from a charge-density-wave gap
opening is observed below the metal-insulator transition temperature of 230 K.
The resultant modification of electronic structure is consistent with the
density functional theory prediction. In the spin- and charge- dimer disordered
phase induced by x-ray irradiation below 50 K, we find that a broad peak around
0.4 eV appears in the RIXS spectrum.Comment: 4 pages and 4 figure
Primary gas thermometry by means of laser-absorption spectroscopy: Determination of the Boltzmann constant
We report on a new optical implementation of primary gas thermometry based on
laser absorption spectrometry in the near infrared. The method consists in
retrieving the Doppler broadening from highly accurate observations of the line
shape of the R(12) transition in
CO gas at thermodynamic equilibrium. Doppler width measurements as a
function of gas temperature, ranging between the triple point of water and the
gallium melting point, allowed for a spectroscopic determination of the
Boltzmann constant with a relative accuracy of .Comment: Submitted to Physical Review Letter
Observation of a 500meV Collective Mode in LaSrCuO and NdCuO
Utilizing resonant inelastic x-ray scattering, we report a previously
unobserved mode in the excitation spectrum of LaSrCuO at 500
meV. The mode is peaked around the (,0) point in reciprocal space and is
observed to soften, and broaden, away from this point. Samples with x=0, 0.01,
0.05, and 0.17 were studied. The new mode is found to be rapidly suppressed
with increasing Sr content and is absent at =0.17, where it is replaced by a
continuum of excitations. The peak is only observed when the incident x-ray
polarization is normal to the CuO planes and is also present in NdCuO.
We suggest possible explanations for this excitation.Comment: 5 pages, 5 figure
Doping dependence of charge-transfer excitations in La_{2-x}Sr_xCuO_4
We report a resonant inelastic x-ray scattering (RIXS) study of the doping
dependence of charge-transfer excitations in . The mome
ntum dependence of these charge excitations are studied over the whole
Brillouin zone in underdoped (x=0.05) and optimally doped (x=0.17) samples, and
compared with that of the undoped (x=0) sample. We observe a large change in
the RIXS spectra between the x=0 and x=0.17 sample, while the RIXS spectra of
the x=0.05 sample are similar to that of the x=0 sample. The most prominent
effect of doped-holes on the charge excitation spectra is the appearance of a
continuum of intensity, which exhibits a strong momentum-dependence below 2 eV.
For the x=0.17 sample, some of the spectral weight from the lowest-lying
charge-transfer excitation of the undoped compound is transferred to the
continuum intensity below the gap, in agreement with earlier optical studies.
However, the higher energy charge-transfer excitation carries significant
spectral weight even for the x=0.17 sample. The doping dependence of the
dispersion of this charge-transfer excitation is also discussed and compared
with recent theoretical calculations.Comment: 7 pages, 6 figures, to appear in Phys. Rev.
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