第1回 物理工学科教室談話会(講師:Prof. Dr. Seunghun Lee)

日時: 2015年6月3日 14:00-15:30
場所: 東京大学本郷キャン パス工学部6号館大会議室(103)
講師: Prof. Dr. Seunghun Lee (Department of Physics, University of Virginia)
題目: A spin jam state of a highly frustrated magnet

Can a glassy state exist in the absence of defects?
This long-standing problem in condensed matter physics will be addressed in this talk by discussing glassy states found in frustrated magnets.
Of particular interest is a quasi-two-dimensional triangular lattice of bi-pyramids. Recently, we found that although classically the ground state of the system is a spin liquid, quantum corrections break the classical degeneracy into a set of aperiodic spin configurations forming local minima in a rugged energy landscape. A consequence of the complex energy landscape is, upon cooling, the system gets trapped in one of the local minima, leading to a glassy state that we call a spin jam.[1]
More recently, we have performed systematic neutron scattering experiments on SrCr_{9p}Ga_{12-9p}O_{19} (SCGO(p)) with various values of the magnetic concentration, p, covering almost the entire region of p. Our results clearly revealed existence of a unique spin jam state in the vicinity of the clean limit p=1.[2]
[1] I. Klich, S.-H. Lee, K. Iida, Nature Comm. 5, 3497 (2014).
[2] J. Yang et al., submitted (2015).
紹介教員:今田正俊教授、 求幸年准教授