Head: Dr. Rudolf Schneider
Thin films and interfaces often show novel and unusual properties that are different from those of the bulk materials. We presently investigate the novel unconventional Fe-based superconductors, iridates with perovskite structure and interfaces between oxide insulators with a 2D electron gas. The most important questions concern the electronic transport in epitaxial FeSe thin films, the spin-orbit coupling in iridate films and the anisotropy of the electronic transport in the 2D electron system at the interface of oxide heterostructures. Low-dimensional strongly correlated electron systems with strong spin-orbit coupling are promissing candidates for the appearance of novel quantum states and therefore most interesting with respect to the basics of modern solid state physics (quantum materials).
For the film preparation we use sputtering and laser ablation. The analysis of the films comprises surface morphology, crystallographic properties, microstructure, magnetism, electronic structure, and electronic transport. The investigations are performed in close cooperation with other groups of IFP and other institutes of KIT.
Pulsed laser deposition (PLD) of transition metal oxides
Structural properties and anisotropic electronic transport in SrIrO3 films
K. R. Kleindienst, K. Wolff, J. Schubert, R. Schneider, D. Fuchs
Phys. Rev. B 98 (2018) 115113.
Anisotropic electronic transport and Rashba effect of the two-dimensional electron system in (110) SrTiO3-based heterostructures
K. Wolff, R. Eder, R. Schäfer, R. Schneider, D. Fuchs
Phys. Rev. B 98 (2018) 125122.
Anisotropic grain-boundary effect on electronic transport in superconducting FeSe thin films
R. Schneider, A. G. Zaitsev, D. Fuchs, R. Hott
Supercond. Sci. Technol. (2018) .
Toward new gas-analytical multisensor chips based on titanium oxide nanotube array
F. Fedorov, M. Vasilkov M, A. Lashkov, A. Varezhnikov, D. Fuchs, C. Kübel,
M. Bruns, M. Sommer, V. Sysoev
Sci. Rep. 7 (2017) 9732.
Current research interests
Recent technical advances in thin-film technology, especially PLD, have enabled the atomic-scale synthesis of epitaxial complex oxide heterostructures such as multilayers and superlattices of perovskite oxides. Compared to their conventional semiconductor counterparts, these oxide heterostructures offer even more opportunities to uncover new quantum states at their interfaces, owing to a subtle interplay between spin, charge, lattice, and orbital degrees of freedom in these complex oxides.
The observation by Hwang (Nature 427 (2004) 423) and Mannhart and Triscone (Science 317 (2007) 1196) that the interface between the insulators LaAlO3 (LAO) and SrTiO3 (STO) is metallic and even becomes superconducting has triggered enormous interest. The transport properties at the interface of LAO/STO heterostructures were found to be very sensitive towards the oxygen partial pressure during film growth. Regarding the strong confinement of the quasi two-dimensional electron-liquid, applying pressure to the heterostructure should strongly affect the transport properties as well. Thus, transport measurements under hydrostatic pressure seem to be very interesting. Besides the strong electronic anisotropy due to the confinement of the 2D electron gas, electronic anisotropies can be generated at the interface which might be of great interest with respect to applications in the field of spintronics. In this context we also investigate 3d, 4d and 5d transition metal oxides which show strong spin-orbit coupling.
(a) Interfacial structure of CaCuO2 on NdO-terminated NdGaO3. (b) HAADF-STEM cross-sectional image of CaCuO2/NdGaO3 prepared by PLD. (c) Element sequence (intensity scan) along the dashed line in (b) before and after background subtraction.
- Anisotropic electronic transport of the two-dimensional electron system in Al2O3/SrTiO3 heterostructures
K. Wolff, R. Schaefer, M. Meffert, D. Gerthsen, R. Schneider, D. Fuchs
Phys. Rev. B 95 (2017) 245132.
- Incipient localization of charge carriers in the two-dimensional electron system in LaAlO3 /SrTiO3 under hydrostatic pressure
D. Fuchs, A. Sleem, R. Schäfer, A. G. Zaitsev, M. Meffert, D. Gerthsen, R. Schneider, and H.v.Löhneysen
Phys. Rev. B 92 (2015) 155313.
- Two-dimensional superconductivity between SrTiO3 and amorphous Al2O3
D. Fuchs, R. Schäfer, A. Sleem, R. Schneider, R. Thelen, H.v.Löhneysen
Appl. Phys. Lett. 105 (2014) 92602.
- Growth and Interfacial Properties of Epitaxial CaCuO2 Thin Films
D. Fuchs, P. Müller, A. Sleem, R. Schneider, D. Gerthsen, H.v.Löhneysen
J. Appl. Phys. 112 (2012) 103529.
Thin films of the novel unconventional superconductor FeSe with Tc = 8 K were grown on (110) oriented single-crystalline SrTiO3 substrates by means of sputtering. Their crystallographic structure and surface morphology were investigated by x-ray diffraction and scanning electron microscopy. The films grow epitaxially on the substrate with crystallographic c-axis perpendicular to the substrate plane and uniform orientation of the a- and b-axes. The films consist of plate-like crystalline grains featuring a remarkable uniaxial alignment. This leads to a distinct anisotropy of the electric resistivity which can be explained quantitatively by a theoretical model based on a particular grain boundary structure. Comparing measurements of the magnetoresistance, upper critical field and critical current density with or without application of a magnetic field are performed.
Left: Microstructure of the FeSe films: Grains with preferential orientation (upper figure)
Lower figure: Patterned microbridges H and V.
Right: Anisotropic specific resistance of the FeSe films and modeling.
- Analysis of superconducting FeSe thin films deposited by a sputtering technique
R. Schneider, A. G. Zaitsev, D. Fuchs, R. Fromknecht
Supercond. Sci. Technol. 26 (2013) 55014.
- Excess conductivity and Berezinskii-Kosterlitz-Thouless transition in superconducting FeSe thin films
R. Schneider, A.G Zaitsev, D. Fuchs, H. von Löhneysen
J. Phys.: Condens. Matter 26 (2014) 455701.
- Superconducting and insulating phases of disordered FeSe thin films
R. Schneider, A.G. Zaitsev, D. Fuchs, H. v. Loehneysen
Eur. Phys. J. B 88 (2015) 14.
- Superconducting and Insulating Phases of Disordered FeSe Thin Films in a Magnetic Field
R. Schneider, A.G. Zaitsev, D. Fuchs, H. von Löhneysen
J. Low Temp. Phys. 178 (2014) 118.
Current group members (in alphabetical order)
Former group membersDr. Markus Adam, Dr. Erhan Arac, Dr. Jochen Geerk, Dr. Cornelia Hintze, Thomas Kimpel, Dr. Gerhard Linker, Dr. Otto Meyer, Dr. Oswaldo Moran, Dr. Thorsten Schwarz, Dr. Ahmed Sleem, Dr. Markus Wissinger, Karsten Wolff, et al.