Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 6: Superconductivity: Tunnelling & Josephson Junctions
TT 6.8: Talk
Monday, March 11, 2013, 11:30–11:45, H18
Fractional Flux Quantization in Loops of Unconventional Superconductors — •Florian Loder, Arno P. Kampf, and Thilo Kopp — Center for Electronic Correlations and Magnetism, University of Augsburg, Germany
The magnetic flux threading a conventional superconducting ring is typically quantized in units of Φ0=hc/2e. The factor 2 in the denominator of Φ0 originates from the existence of two different types of pairing states with minima of the free energy at even and odd multiples of Φ0. Here we show that spatially modulated pairing states exist with energy minima at fractional flux values, in particular at multiples of Φ0/2. In such states condensates with different center-of-mass momenta of the Cooper pairs coexist. The proposed mechanism for fractional flux quantization is discussed in the context of cuprate superconductors, where hc/4e flux periodicities as well as uniaxially modulated superconducting states were observed.