How THz circularly polarized light can be used to determine the mass of vortices in high-temperature superconductors

Dr. Christelle Kadlec1, Dr. Roman Tesař1, Dr. Michal Šindler1, Dr. Jan Koláček1, Prof. Pavel Lipavský2
1FZU - Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic. 2Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic


The determination of the mass of Abrikosov vortices in superconductors is a long standing issue. Whereas the theoretical approximations spand over 8 orders of magnitude, only two experimental evaluations were previously performed. Here we propose an approach based on far-infrared magnetic circular dichroism. 

Our method is inspired by the determination of the cyclotron mass of charge carriers in semiconductors in magnetic field through measuring the cyclotron resonance. In the case of vortices, we probe their interaction with circularly polarised far-infrared light under external magnetic field of up to 10 T. The transmittance of the light through the superconducting sample differs for the clockwise and anti-clockwise polarised light, resulting in the so-called circular dichroism. We propose a model to relate the ratio of the transmittance of the two polarisations to the mass of the vortices.

We focuse on YBaCuO, the most common high-temperature superconductor. Pulsed laser deposition was used to prepare a 107 nm-thick film with CuO2 planes parallel to the surface of the (100) lanthanum aluminate substrate. The sample parameters were determined by usual techniques or taken from the literature. Additional film properties were established using time-domain THz spectroscopy. With such inputs, we show that the theory of the vortex mass developed by Kopnin matches our experimental data without any additional fitting parameter

For YBaCuO at 45 K, in the zero-frequency limit, the diagonal mass of Abrikosov vortices amounts to 2.2x108 me/cm, while the off-diagonal one reaches 4.9x108 me/cm. In a further work, we plan to determine the vortex mass of YBCO samples with different hole dopings.