19,855 research outputs found
Paramagnetic state in d-wave Superconductors
We study theoretically the paramagnetic state in d-wave superconductors. We
present the specific heat, the magnetization, superfluid density obtained
within the weak-coupling model. At low temperatures and for small magnetic
fields they exhibit simple power law behaviors, which should be accessible
experimentally in hole-doped high-T_c cuprates and \kappa-(ET)_2 salts in a
magnetic field within the conducting plane.Comment: 5 pages(EuroTeX), 13 figures, submitted to Europhysics Letter
Surface segregation and the Al problem in GaAs quantum wells
Low-defect two-dimensional electron systems (2DESs) are essential for studies
of fragile many-body interactions that only emerge in nearly-ideal systems. As
a result, numerous efforts have been made to improve the quality of
modulation-doped AlGaAs/GaAs quantum wells (QWs), with an emphasis
on purifying the source material of the QW itself or achieving better vacuum in
the deposition chamber. However, this approach overlooks another crucial
component that comprises such QWs, the AlGaAs barrier. Here we show
that having a clean Al source and hence a clean barrier is instrumental to
obtain a high-quality GaAs 2DES in a QW. We observe that the mobility of the
2DES in GaAs QWs declines as the thickness or Al content of the
AlGaAs barrier beneath the QW is increased, which we attribute to
the surface segregation of Oxygen atoms that originate from the Al source. This
conjecture is supported by the improved mobility in the GaAs QWs as the Al cell
is cleaned out by baking
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