33,366 research outputs found
Tuning Hole Mobility, Concentration, and Repulsion in High- Cuprates via Apical Atoms
Using a newly developed first-principles Wannier-states approach that takes
into account large on-site Coulomb repulsion, we derive the effective
low-energy interacting Hamiltonians for several prototypical high-
superconducting cuprates. The material dependence is found to originate
primarily from the different energy of the apical atom state.
Specifically, the general properties of the low-energy hole state, namely the
Zhang-Rice singlet, are significantly modified by a triplet state associated
with this state, via additional intra-sublattice hoppings,
nearest-neighbor "super-repulsion", and other microscopic many-body processes.
Possible implications on modulation of , local superconducting gaps,
charge distribution, hole mobility, electron-phonon interaction, and
multi-layer effects are discussed.Comment: 5 pages, 3 figures, 1 tabl
Regression tree models for designed experiments
Although regression trees were originally designed for large datasets, they
can profitably be used on small datasets as well, including those from
replicated or unreplicated complete factorial experiments. We show that in the
latter situations, regression tree models can provide simpler and more
intuitive interpretations of interaction effects as differences between
conditional main effects. We present simulation results to verify that the
models can yield lower prediction mean squared errors than the traditional
techniques. The tree models span a wide range of sophistication, from piecewise
constant to piecewise simple and multiple linear, and from least squares to
Poisson and logistic regression.Comment: Published at http://dx.doi.org/10.1214/074921706000000464 in the IMS
Lecture Notes--Monograph Series
(http://www.imstat.org/publications/lecnotes.htm) by the Institute of
Mathematical Statistics (http://www.imstat.org
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