TY  - JOUR
A1  - Bisti, F.
A1  - Rogalev, V. A.
A1  - Karolak, M.
A1  - Paul, S.
A1  - Gupta, A.
A1  - Schmitt, T.
A1  - Güntherodt, G.
A1  - Eyert, V.
A1  - Sangiovanni, G.
A1  - Profeta, G.
A1  - Strocov, V. N.
T1  - Weakly-correlated nature of ferromagnetism in nonsymmorphic CrO\(_2\) revealed by bulk-sensitive soft-X-ray ARPES
JF  - Physical Review X
N2  - Chromium dioxide CrO\(_2\) belongs to a class of materials called ferromagnetic half-metals, whose peculiar aspect is that they act as a metal in one spin orientation and as a semiconductor or insulator in the opposite one. Despite numerous experimental and theoretical studies motivated by technologically important applications of this material in spintronics, its fundamental properties such as momentumresolved electron dispersions and the Fermi surface have so far remained experimentally inaccessible because of metastability of its surface, which instantly reduces to amorphous Cr\(_2\)O\(_3\). In this work, we demonstrate that direct access to the native electronic structure of CrO\(_2\) can be achieved with soft-x-ray angle-resolved photoemission spectroscopy whose large probing depth penetrates through the Cr\(_2\)O\(_3\) layer. For the first time, the electronic dispersions and Fermi surface of CrO\(_2\) are measured, which are fundamental prerequisites to solve the long debate on the nature of electronic correlations in this material. Since density functional theory augmented by a relatively weak local Coulomb repulsion gives an exhaustive description of our spectroscopic data, we rule out strong-coupling theories of CrO\(_2\). Crucial for the correct interpretation of our experimental data in terms of the valence-band dispersions is the understanding of a nontrivial spectral response of CrO\(_2\) caused by interference effects in the photoemission process originating from the nonsymmorphic space group of the rutile crystal structure of CrO\(_2\).
KW  - physics
KW  - electronic structure
KW  - half-metals
KW  - angle-resolved photoemission spectroscopy
KW  - band structure methods
KW  - DFT+U
KW  - condensed matter physics
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172251
VL  - 7
IS  - 4
ER  - 
TY  - JOUR
A1  - Lüftner, Daniel
A1  - Milko, Matus
A1  - Huppmann, Sophia
A1  - Scholz, Markus
A1  - Ngyuen, Nam
A1  - Wießner, Michael
A1  - Schöll, Achim
A1  - Reinert, Friedrich
A1  - Puschnig, Peter
T1  - CuPc/Au(1 1 0): Determination of the azimuthal alignment by a combination of angle-resolved photoemission and density functional theory
JF  - Journal of Electron Spectroscopy and Related Phenomena
N2  - Here we report on a combined experimental and theoretical study on the structural and electronic properties of a monolayer of Copper-Phthalocyanine (CuPc) on the Au(1 1 0) surface. Low-energy electron diffraction reveals a commensurate overlayer unit cell containing one adsorbate species. The azimuthal alignment of the CuPc molecule is revealed by comparing experimental constant binding energy (kxky)-maps using angle-resolved photoelectron spectroscopy with theoretical momentum maps of the free molecule's highest occupied molecular orbital (HOMO). This structural information is confirmed by total energy calculations within the framework of van-der-Waals corrected density functional theory. The electronic structure is further analyzed by computing the molecule-projected density of states, using both a semi-local and a hybrid exchange-correlation functional. In agreement with experiment, the HOMO is located about 1.2 eV below the Fermi-level, while there is no significant charge transfer into the molecule and the CuPc LUMO remains unoccupied on the Au(1 1 0) surface.
KW  - density functional theory
KW  - angle-resolved photoemission spectroscopy
KW  - organic molecule
KW  - organic–metal interface
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-120986
SN  - 0368-2048
VL  - 195
ER  -