TY  - JOUR
A1  - Izquierdo, Manuel
A1  - Karolak, Michael
A1  - Prabhakaran, Dharmalingam
A1  - Boothroyd, Andrew T.
A1  - Scherz, Andreas O.
A1  - Lichtenstein, Alexander
A1  - Molodtsov, Serguei L.
T1  - Monitoring ultrafast metallization in LaCoO3 with femtosecond soft x-ray spectroscopy
JF  - Communications Physics
N2  - The study of ultrafast dynamics is a new tool to understand and control the properties of correlated oxides. By enhancing some properties and realizing new dynamically excited phrases, this tool has opened new routes for technological applications. LaCoO3 is one paradigmatic example where the strong electron, spin, and lattice coupling induced by electronic correlations results in a low-temperature spin transition and a high-temperature semiconductor-to-metal transition that is still not completely understood. Here, we monitor ultrafast metallization in LaCoO3 using time-resolved soft x-ray reflectivity experiments. While the process is entangled at the Co L3 edge, the time information of the different channels is decrypted at different resonant energies of the O K edge. Metallization is shown to occur via transient electronic, spin, and lattice separation. Our results agree with the thermodynamical model and demonstrate the potential of femtosecond soft x-ray experiments at the O K edge to understand correlated oxides.
KW  - electronic properties and materials
KW  - magnetic properties and materials
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-323265
VL  - 2
ER  - 
TY  - JOUR
A1  - Kügel, Jens
A1  - Karolak, Michael
A1  - Krönlein, Andreas
A1  - Serrate, David
A1  - Bode, Matthias
A1  - Sangiovanni, Giorgio
T1  - Reversible magnetic switching of high-spin molecules on a giant Rashba surface
JF  - npj Quantum Materials
N2  - The quantum mechanical screening of a spin via conduction electrons depends sensitively on the environment seen by the magnetic impurity. A high degree of responsiveness can be obtained with metal complexes, as the embedding of a metal ion into an organic molecule prevents intercalation or alloying and allows for a good control by an appropriate choice of the ligands. There are therefore hopes to reach an “on demand” control of the spin state of single molecules adsorbed on substrates. Hitherto one route was to rely on “switchable” molecules with intrinsic bistabilities triggered by external stimuli, such as temperature or light, or on the controlled dosing of chemicals to form reversible bonds. However, these methods constrain the functionality to switchable molecules or depend on access to atoms or molecules. Here, we present a way to induce bistability also in a planar molecule by making use of the environment. We found that the particular “habitat” offered by an antiphase boundary of the Rashba system BiAg2 stabilizes a second structure for manganese phthalocyanine molecules, in which the central Mn ion moves out of the molecular plane. This corresponds to the formation of a large magnetic moment and a concomitant change of the ground state with respect to the conventional adsorption site. The reversible spin switch found here shows how we can not only rearrange electronic levels or lift orbital degeneracies via the substrate, but even sway the effects of many-body interactions in single molecules by acting on their surrounding.
KW  - electronic structure of atoms and molecules
KW  - magnetic properties and materials
KW  - surfaces, interfaces and thin films
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230866
VL  - 3
ER  -