Terahertz spectroscopy of the Dirac semimetal SrIrO₃

We use terahertz time domain spectroscopy on molecular beam epitaxially grown SrIrO₃ on a GdScO₃ substrate to study the terahertz conductivity from 6.5 K to 290 K. SrIrO₃ is of interest because the band structure has a lifted Dirac-like cone at the U point in DFT calculations and ARPES data, with an estimated gap calculated to be 5 meV (1.2 THz) when grown on a lattice matched substrate. Lattice matching of SrIrO₃ can be achieved by growth on a GdScO₃ substrate, where the strain due to lattice mismatch is negligible. Using terahertz time domain spectroscopy allows us to directly measure the band gap at the U point.. In addition, we use near infrared pump-THz probe was used to study relaxation times of the lattice and electrons from 6.5 K to 50 K and use the two-temperature to model our results.