Krisztián Palotás, Werner A. Hofer, László Szunyogh
We propose a computationally efficient atom-superposition-based method for
simulating spin-polarized scanning tunneling spectroscopy (SP-STS) on complex
magnetic surfaces based on the sample and tip electronic structure obtained
from first principles. By directly calculating bias-integrated terms, we avoid
numerical errors of the differentiation of the tunneling current with respect
to the bias voltage in determining the differential conductance (dI/dV). The
capabilities of our approach are illustrated for a Cr monolayer on a Ag(111)
surface in a noncollinear magnetic state. We find evidence that the simulated
tunneling spectra and magnetic asymmetries are sensitive to the tip electronic
structure, and we analyze the contributing terms. Related to SP-STS
experiments, we show how to simulate two-dimensional differential conductance
maps and qualitatively correct effective spin polarization maps on a constant
current contour above a magnetic surface. Moreover, we derive alternative
expressions for dI/dV and suggest a combined experimental-theoretical procedure
that might help to extract surface and tip electronic structure information
from experimentally measured spectra.
View original:
http://arxiv.org/abs/1202.1257
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