The p-wave superfluid 3He exhibits a number of exotic quantum phenomena which are intimately related to symmetry breaking and nontrivial topology, and understanding of those phenomena has significant implications not only on condensed matter physics but also on particle physics and cosmology [1]. In this talk, I will present two experimental studies of novel phenomena arising from symmetry breaking and nontrivial topology of superfluid 3He. First, I will present the first direct demonstration of time-reversal symmetry breaking in Weyl superfluid 3He-A phase by showing that electrons immersed in superfluid 3He-A exhibit an anomalous Hall effect [2]. Second, I will present the direct observation of Majorana surface states formed at a free surface of topological 3He-B phase by using electrons trapped at the surface [3, 4, 5].
[1] G. E. Volovik, The Universe in a Helium Droplet (Oxford University Press, Oxford, 2003).
[2] H. Ikegami, Y. Tsutsumi, and K. Kono, Science 341, 59 (2013).
[3] H. Ikegami and K. Kono, J. Low Temp. Phys. 195, 343 (2019) (arXiv:1805.11231).
[4] H. Ikegami, S. B. Chung, and K. Kono, J. Phys. Soc. Jpn. 82, 124607 (2013).
[5] Y. Tsutsumi, Phys. Rev. Lett. 118, 145301 (2017).
Hiroki Ikegami is a senior research scientist at RIKEN. He received B. S., M. S., and Ph. D. from the University of Tokyo, all in applied physics. He was an Assistant Professor at Graduate School of Arts and Sciences, the University of Tokyo in 1999–2001 and a research scientist at RIKEN in 2001–2007. Since 2007, he has been a senior research scientist at RIKEN. His research is focused on experimental studies of condensed matter physics at ultralow temperatures, in particular on topological aspects of the superfluid 3He, electrons trapped on a helium surface with the prospect of realizing qubits, and superconducting quantum circuits. He received a Young Scientist Award of the Physical Society of Japan in 2009 and JSPS (Japan Society for the Promotion of Science) Prize in 2015.
