7,227 research outputs found
Phonon, Two-Magnon and Electronic Raman Scattering of Fe1+yTe1-xSex
We have measured Raman scattering spectra of single-crystalline FeTe0.6Se0.4
(T_c ~ 14.5 K) and its parent compound Fe1.074Te at various temperatures. In
the parent compound Fe1.074Te, A1g and B1g modes have been observed at 157.5
and 202.3 cm-1, respectively, at 5 K. These frequencies qualitatively agree
with the calculated results. Two-magnon excitation has been observed around
2300 cm-1 for both compounds. Temperature dependence between the electronic
Raman spectra below and above T_c has been observed and 2\Delta and
2\Delta/k_BT_C have been estimated as 5.0 meV and 4.0, respectively.Comment: 8 pages, 8 figures, to be published in Phys. Rev.
Aging of poled ferroelectric ceramics due to relaxation of random depolarization fields by space-charge accumulation near grain boundaries
Migration of charged point defects triggered by the local random
depolarization field is shown to plausibly explain aging of poled ferroelectric
ceramics providing reasonable time and acceptor concentration dependences of
the emerging internal bias field. The theory is based on the evaluation of the
energy of the local depolarization field caused by mismatch of the
polarizations of neighbor grains. The kinetics of charge migration assumes
presence of mobile oxygen vacancies in the material due to the intentional or
unintentional acceptor doping. Satisfactory agreement of the theory with
experiment on the Fe-doped lead zirconate titanate is demonstrated.Comment: theory and experiment, 22 pages, 3 figure
Equivalence between Schwinger and Dirac schemes of quantization
This paper introduces the modified version of Schwinger's quantization
method, in which the information on constraints and the choice of gauge
conditions are included implicitly in the choice of variations used in
quantization scheme. A proof of equivalence between Schwinger- and
Dirac-methods for constraint systems is given.Comment: 12pages, No figures, Latex, The proof is improved and one reference
is adde
Competition between unconventional superconductivity and incommensurate antiferromagnetic order in CeRh1-xCoxIn5
Elastic neutron diffraction measurements were performed on the quasi-two
dimensional heavy fermion system CeRh1-xCoxIn5, ranging from an incommensurate
antiferromagnet for low x to an unconventional superconductor on the Co-rich
end of the phase diagram. We found that the superconductivity competes with the
incommensurate antiferromagnetic (AFM) order characterized by qI=(1/2, 1/2,
delta) with delta=0.298, while it coexists with the commensurate AFM order with
qc=(1/2, 1/2, 1/2). This is in sharp contrast to the CeRh1-xIrxIn5 system,
where both the commensurate and incommensurate magnetic orders coexist with the
superconductivity. These results reveal that particular areas on the Fermi
surface nested by qI play an active role in forming the superconducting state
in CeCoIn5.Comment: RevTeX4, 4 pages, 4 eps figures; corrected a typo and a referenc
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