%0 Journal Article
%T Observation of the orbital quantum dynamics in the spin-1/2 hexagonal antiferromagnet Ba3CuSb2O9
%A Yibo Han
%A Masayuki Hagiwara
%A Takehito Nakano
%A Yasuo Nozue
%A Kenta Kimura
%A Mario Halim
%A Satoru Nakatsuji
%J Physics
%D 2015
%I arXiv
%R 10.1103/PhysRevB.92.180410
%X We explore orbital dynamics in the spin liquid candidate Ba3CuSb2O9 using multi-frequency electron spin resonance. We prepared two high quality single crystals. The crystal with a slight copper deficiency shows a structural phase transition at around 200 K due to the cooperative Jahn-Teller effect, accompanied with orbital ordering. In contrast, the crystal with almost perfect stoichiometry shows no orbital ordering down to the lowest temperature of 1.5 K. Dramatic change in the g-factor anisotropy as a function of frequency and temperature demonstrates orbital quantum fluctuations at a nearly constant time scale of ~ 100 ps below 20 K, evidencing the emergence of an orbital liquid state in this quantum spin liquid compound.
%U http://arxiv.org/abs/1508.01653v1