3 research outputs found
Coexistence of magnetism and superconductivity in a t-J bilayer
We investigate coexistence of antiferromagnetic and superconducting
correlations in bilayered materials using a two-dimensional t-J model with
couplings across the layers using variational Monte Carlo calculations. It is
found that the underdoped regime supports a coexisting phase, beyond which the
(d-wave) superconducting state becomes stable. Further, the effects of
interplanar coupling parameters on the magnetic and superconducting
correlations as a function of hole doping are studied in details. The magnetic
correlations are found to diminish with increasing interplanar hopping away
from half filling, while the exchange across the layers strengthens interplanar
antiferromagnetic correlations both at and away from half filling. The
superconducting correlations show more interesting features where larger
interplanar hopping considerably reduces planar correlations at optimal doping,
while an opposite behaviour, i.e. stabilisation of the superconducting state is
realised in the overdoped regime, with the interplanar exchange all the while
playing a dormant role.Comment: 8 pages, 9 figures, RevTex4, Submitted to Phys. Rev.
Schottky defect enthalpies of alkaline earth oxides
306-312<span style="font-size:14.0pt;line-height:
115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:="" hi"="" lang="EN-IN">The Schottky defect formation process in MgO, CaO, SrO, and BaO is investigated using our
recently introduced EPPI model3. We find that inclusion of
quadrupolar interactions makes a substantial contribution to the formation
energy by values ranging from 1.2 eV to 2.9 eV. The EPPI values of the
enthalpies (hfs) are 5.9, 5.8, 4.7 and 1.4
eV respectively for MgO, CaO, SrO, and BaO. The results of cation self
diffusion experiments in MgO are reanalyzed to include the effects of
impurity-vacancy association reaction. The analysis suggests the previous
interpretation of the experimental data to be an oversimplification. Since the
binding energy of an impurity - defect complex in MgO could be quite large, the
effects of the association reaction on the defect densities are appreciable. On
the basis of near complete association of the dominant tetravalent cation impurity,
hfs in MgO is found to be 5.8 eV which is in good
agreement with the theoretical value of the present work.</span