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
Gamma-ray flashes from plasma filaments
18.04.2018 | Max-Planck-Institut für Kernphysik
How does a molecule vibrate when you “touch” it?
17.04.2018 | Universität Regensburg
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
In an article that appears in the journal “Review of Modern Physics”, researchers at the Laboratory for Attosecond Physics (LAP) assess the current state of the field of ultrafast physics and consider its implications for future technologies.
Physicists can now control light in both time and space with hitherto unimagined precision. This is particularly true for the ability to generate ultrashort...
The Atlantic overturning – one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards – is weaker today than any time before in more than 1000 years. Sea surface temperature data analysis provides new evidence that this major ocean circulation has slowed down by roughly 15 percent since the middle of the 20th century, according to a study published in the highly renowned journal Nature by an international team of scientists. Human-made climate change is a prime suspect for these worrying observations.
“We detected a specific pattern of ocean cooling south of Greenland and unusual warming off the US coast – which is highly characteristic for a slowdown of the...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
19.04.2018 | Power and Electrical Engineering
19.04.2018 | Life Sciences
18.04.2018 | Materials Sciences