抄録
Terahertz frequency, i.e., 0.1 ~ 10 THz in frequency corresponds to the intermediate region between
electronics and photonics. Recent development of intense terahertz pulse generation technique has
opened a new avenue for investigating low-energy electromagnetic responses of condensed matter systems
far away from thermal equilibrium. Here we present our recent studies of topological Dirac and
Weyl semimetals using intense terahertz pulse and ultrafast time-resolved spectroscopy. A Dirac semimetal
Cd3As2 hosts 3-dimensional massless electrons with high mobility, which shows efficient harmonic
generation. A Weyl antiferromagnet Mn3Sn shows large anomalous Hall effect comparable to ferromagnets
instead of vanishingly-small net magnetization, and therefore attracts growing attention as a
candidate material for fast spintronic information processing. Remarkable functionalities of the novel
materials at room temperature would contribute to the next-generation high-speed electronics and spintronics
in terahertz frequency.
