Giant Effective Damping of Octupole Oscillation in an Antiferromagnetic Weyl Semimetal
Shinji Miwa, Satoshi Iihama, Takuya Nomoto, Takahiro Tomita, Tomoya Higo, Muhammad Ikhlas, Shoya Sakamoto, Y. Otani, Shigemi Mizukami, Ryotaro Arita, Satoru Nakatsuji
Abstract
A magnetic Weyl semimetal is a recent focus of extensive research as it may exhibit large and robust transport phenomena associated with topologically protected Weyl points in momentum space. Since a magnetic texture provides a handle for the configuration of the Weyl points and its transport response, understanding of magnetic dynamics forms the basis for future control of a topological magnet. Mn 3 Sn is an example of an antiferromagnetic Weyl semimetal that exhibits a large response comparable to the one observed in ferromagnets despite a vanishingly small magnetization. The noncollinear spin order in Mn 3 Sn can be viewed as a ferroic order of cluster magnetic octupole and breaks the time‐reversal symmetry, stabilizing Weyl points and the significantly enhanced Berry curvature near the Fermi energy. Herein, the first observation of time‐resolved octupole oscillation in Mn 3 Sn is reported. In particular, the giant effective damping of the octupole dynamics is found, and it is feasible to conduct an ultrafast switching at <10 ps, a hundred times faster than the case of spin‐magnetization in a ferromagnet. Moreover, high domain wall velocity over 10 km s −1 is theoretically predicted. This work paves the path toward realizing ultrafast electronic devices using the topological antiferromagnet.