1,402 research outputs found
Structural Properties of Two-Dimensional Strontium Titanate: A First-Principles Investigation
Motivated by the experimental synthesis of two-dimensional (2D) perovskite
materials, we study the stability of 2D SrTiO from first principles. We
find that the TiO octahedral rotations emerge in 2D SrTiO with a
rotation angle twice that in the 3D bulk. The rotation angle decreases
significantly with the film thickness, reflecting the strong interlayer
coupling that is absent in the conventional 2D materials. Using the molecular
dynamics simulations, the cubic-like phase is found to appear above 1000 K that
is much higher than the transition temperature of 3D SrTiO.Comment: 5 pages, 4 figure
Inhomogeneous electronic structure probed by spin-echo experiments in the electron doped high-Tc superconductor Pr_{1.85}Ce_{0.15}CuO_{4-y}
63Cu nuclear magnetic resonance (NMR) spin-echo decay rate (T_2^{-1})
measurements are reported for the normal and superconducting states of a single
crystal of Pr_{1.85}Ce_{0.15}CuO_{4-y} (PCCO) in a magnetic field B_0=9T over
the temperature range 2K<T<200K. The spin-echo decay rate is
temperature-dependent for T<55K, and has a substantial dependence on the radio
frequency (rf) pulse parameters below T~25K. This dependence indicates that
T_2^{-1} is strongly effected by a local magnetic field distribution that can
be modified by the rf pulses, including ones that are not at the nuclear Larmor
frequency. The low-temperature results are consistent with the formation of a
static inhomogeneous electronic structure that couples to the rf fields of the
pulses.Comment: 4 pages, 4 figure
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