by Staff Writers
Berlin, Germany (SPX) Jun 24, 2016
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.
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
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
Research paper: 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 and B. Keimer, Nature Materials (2016) doi: 10.1038/nmat4682
Helmholtz-Zentrum Berlin fur Materialien und Energie
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