Seminar "Numerical simulations of spin-1 magnets " by Dr. Rico Pohle

[Spearker]

Dr. Rico Pohle - Waseda University

2012: Diploma in Physics (TU Dresden) – “Scanning tunneling microscopy on LiFeAs”
Dec. 2017: PhD in Physics (OIST) – “Signatures of novel spin liquids in kagome-like lattices”
Dec. 2017 – May 2018: Junior Research Fellow (OIST)
June 2018 – March 2019: PostDoc in Prof. Imada Group (University of Tokyo)
since April 2019: PostDoc in Prof. Imada Group (Waseda University)

[Abstract]

Theoretical studies of magnets have traditionally concentrated on either classical spins, or the extreme quantum limit of spin–1/2. However, magnets built of spin–1 moments are also intrinsically interesting, because they can support quadrupole, as well as dipole moments, on a single site [1]. For this reason, models of spin–1 magnets have been extensively studied as a prototype for spin–nematic order in both magnetic insulators [2] and Fe–based superconductors [3], as well as in spinor Bose–Einstein Condensates [4]. In this talk we introduce a method of simulating spin–1 magnets based on a u(3) algebra, which treats quantum aspects of the problem exactly, at the level of a single site.  Within this approach, it is possible to determine the thermodynamic properties of spin–1 magnets using classical Monte Carlo simulations, and dynamics through the numerical integration of equations of motion. We show that this approach reproduces known results from both quantum Monte Carlo simulations [5] and analytic flavour–wave theory [2] for the excitations of a state with ferroquadrupolar order on the triangular lattice.

[1] N. Papanicolaou, Nuclear Physics B 305, 367 – 395 (1988)
[2] A. Läuchli, F. Mila and K. Penc, Phys. Rev. Lett. 97, 087205 (2006)
[3] Z. Wang, W.J. Hu and A.H. Nevidomskyy, Phys. Rev. Lett. 116, 247203 (2016)
[4] E. Demler and F. Zhou, Phys. Rev. Lett. 88, 163001 (2002)
[5] A. Völl and S. Wessel, Phys. Rev. B 91, 165128 (2015)