Exploring the Photoemission Intensity in ARPES: Information Beyond Band Structure
DIPC Seminars
- Speaker
-
Friedrich Reinert (Univ. Wuerzburg, Germany)
- When
-
2016/04/01
14:00 - Place
- Donostia International Physics Center (DIPC)
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**Exploring the Photoemission Intensity in ARPES: Information Beyond Band
Structure**
Friedrich Reinert, Achim Schöll, and Hendrik Bentmann
_Universität Würzburg, Experimentelle Physik VII
D-97074 Würzburg, Germany
reinert@physik.uni-wuerzburg.de_
Angle resolved photoemission spectroscopy (ARPES) has been successfully
applied for
the investigation of the occupied electronic states in condensed matter
physics, with a
particular emphasis on the band structure and the line-shape of respective
quasi-particle peaks
of single-crystalline solids and surfaces. These latter properties are based
on the fact that the
photoemission spectra represent, under several experimental circumstances and
fundamental
prerequisites, the spectral function of the photoexcited hole in the
(N-1)-system. For the
analysis of these data one usually assumes that the photoemission cross-
section does not
considerably influences the dispersion or the line-shape. However, there are
examples where
the photoemission cross-section significantly alters the experimental results,
but a detailed
theoretical description of these effects is in general rather intricate.
This contribution shall demonstrate how the dependence of the photoemission
intensity
can in principle deliver important additional knowledge beyond band dispersion
and lineshape.
The first example is the so-called "orbital tomography" [1] in which ARPES has
been
used to reconstruct the orbital shape of adsorbed organic molecules including
even subtle
details induced by the interaction with the substrate or even by molecular
vibrations. Here,
the ARPES intensity distribution, given by the photoemission cross-section, is
essentially the
Fourier transform of the orbital [2].
The second example discusses systems with spin-polarized surface states, as
e.g. Rashba
systems and topological insulators (TI), for which the intensity dependence
can bear
important information about the character of the initial state including its
spin properties [3].
In the presented model cases relatively simple numerical analyses were
applied, instead of
using a comprehensive one-step photoemission computation.
A crucial role in the experimental intensity analysis plays the recent
development of novel
analyser systems with an enhanced degree of simultaneity in the data
acquisition, which not
only allow for an efficient detection of the photoelectron current but also
grants access to
necessary normalizing and reference information [4]. The combination of these
analysers
with soft x-ray synchrotron radiation offers high-resolution ARPES
investigations of a new
quality.
REFERENCES
1\. J. Ziroff, F. Forster, A. Schöll, P. Puschnig, F. Reinert, PRL 104,
233004 (2010).
2\. P. Puschnig, S. Berkebile, A. J. Fleming, G. Koller, et al.; SCIENCE 326,
702 (2009).
3\. H. Bentmann, H. Maaß, P. Krüger, F. Reinert, et al.;
arxiv.org/abs/1507.04664
4\. C. Tusche, A. Krasyuk, J. Kirschner; Ultramicroscopy 159, 520 (2015)