In high magnetic fields, the exciton absorption spectrum of a semiconducting single-walled carbon nanotube splits as a result of Aharonov-Bohm magnetic flux. A magnetic field of 370 T, generated by the electro-magnetic flux compression destructive pu
lsed magnet-coil technique, was applied to single-chirality semiconducting carbon nanotubes. Using streak spectroscopy, we demonstrated the separation of the independent band-edge exciton states at the K and K points of the Brillouin zone after the mixing of the dark and bright states above 150 T. These results enable a quantitative discussion of the whole picture of the Aharonov-Bohm effect in single-walled carbon nanotubes.
We investigated the complex conductivity spectrum of a Co-doped BaFe$_2$As$_2$ epitaxial thin film in the THz region. In the normal state, the complex conductivity shows a Drude-type frequency dependence, while in the superconducting state, the frequ
ency dependence of the complex conductivity changes to that of a typical superconducting materials. We estimated the magnetic penetration depth at absolute zero to be 710 nm and the superconducting gap energy to be 2.8 meV, which is considered to be the superconducting gap opened at the electron-type Fermi surface near the M point. We succeeded in obtaining the low-energy elementary excitation of a Fe-based superconductor using the electromagnetic method without invoking the Kramers-Kronig transformation.
