Physicists at BESSY II of Helmholtz-Zentrum Berlin studied an artificial structure composed of alternating layers of ferromagnetic and superconducting materials. Charge density waves induced by the interfaces were found to extend deeply into the superconducting regions, indicating new ways to manipulate superconductivity. The results are now being published in Nature Materials.
High-Tc superconductors were discovered 30 years ago: A class of ceramic metal oxide materials was found to pass electrical current without energy losses. In contrast to conventional superconductors that have to be cooled almost to absolute zero, this property appears already at comparably high temperatures.
Scanning electron microscopy in combination with EELS electron spectroscopy permits to visualise atomic positions of the individual atoms in the heterostructure: Superconducting regions of YBaCuO are identified by yttrium (blue) and copper (pink), the ferromagnetic layers by manganese (green) and lanthanum (red).
Courtesy MPI Stuttgart
In prototypical yttrium barium copper oxide (YBaCuO), the transition temperature is 92 Kelvin (minus 181 degrees centigrade). Hence, liquid nitrogen suffices as coolant to reach the superconducting phase. The discovery of high-temperature superconductivity has started a quest for applications, which are being implemented now.
Until now, however, the microscopic mechanism of high-Tc superconductivity is still matter of debate.
Superconducting and feromagnetic thin layers
A team of scientists lead by Prof. Bernhard Keimer, MPI for Solid State Research, and Dr. Eugen Weschke, HZB, have now investigated an artificial layer system composed of alternating nanolayers of YBaCuO and a ferromagnetic material. The thicknesses of the YBaCuO layers varied between 10 nm and 50 nm.
Tiny collective modulations of valence electrons observed
As interfaces often determine the properties of such heterostructures, physicists were particularly interested in their role for the present system. During his PhD work using resonant x-ray diffraction at BESSY II, Alex Frano could detect tiny collective modulations of valence electrons around Cu atoms in the YBaCuO layer. Data analysis revealed that the resulting charge density wave does not remain located close to the interface but extends across the whole layer. " This finding is quite a surprise, as previous studies revealed a strong tendency of superconductivity to suppress the formation of charge density waves", explains Frano.
Coexistence of superconductivity and charge density wave
"Engineering artifical interfaces in heterostructures of ferromagnetic and superconducting layers allowed to stabilize charge density waves even in the presence of superconductivity: YBaCuO remains superconducting, while the charges arrange in a periodic structure", explains Weschke, " exploring the details of this coexistence on a microscopic scale is a challenging task for future experiments." A most exciting perspective of the present results is paving the way to controlling the superconducting state itself.
Long-range charge-density-wave proximity effect at cuprate/manganate interfaces, A. Frano, S. Blanco-Canosa, E. Schierle, Y. Lu, M. Wu, M. Bluschke, M. Minola, G. Christiani, H. U. Habermeier, G. Logvenov, Y. Wang, P. A. van Aken, E. Benckiser, E. Weschke, M. Le Tacon & B. Keimer, Nature Materials (2016) doi: 10.1038/nmat4682
Dr. Eugen Weschke | Helmholtz-Zentrum Berlin für Materialien und Energie
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences