Magneto –THz spectroscopy in spinel superconductor LiTi₂O₄ thin films

We investigate a spinel superconductor, LiTi₂O₄ using continues wave(CW) terahertz spectroscopy under magnetic fields. By measuring both the magnitude and phase of the transmission, the inversion to complicated conductivity can be done directly and without Kramers-Kronig transformation. LiTi₂O₄ (LTO)is an oxide superconductor with a spinel crystal structure. Although the phase transition temperature is 10K, it was estimated that the spin fluctuations played an important role in the microscopic mechanism for superconductivity. We observed a clear superconducting gap opening at about 1.9meV and a coherent peak. The superconducting state was strongly suppressed by magnetic field up to 9T. It was the first time that the superconducting gap was observed in the compounds LiTi₂O₄ with CW terahertz spectroscopy.