Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 64: Frustrated Magnets - α-RuCl₃ and Cu-based Materials

TT 64.4: Talk

Wednesday, March 14, 2018, 15:45–16:00, HFT-FT 101

Ultrafast relaxation dynamics in a Kitaev spin-liquid candidate α-RuCl₃ — •Steinn Ymir Agustsson¹, Vladimir Grigorev¹, Tao Dong², Nanlin Wang², and Jure Demsar¹ — ¹University of Mainz, Germany — ²Peking University, China

α-RuCl₃, which forms an almost ideal 2D honeycomb lattice with weak interlayer coupling, has been proposed to be a prime candidate for the realization of Kitaev physics. While α-RuCl₃ is an antiferromagnet at temperatures below 7-14 K (depending on the stacking configuration), numerous experiments suggest spin liquid behavior at temperatures above the Néel transition. To probe the dynamics in α-RuCl₃, we performed systematic temperature and excitation density dependent measurements of reflectivity dynamics with femtosecond time resolution, following photoexcitation via inter-site Ru d-d excitations. The low temperature dynamics is found to span timescales from 0.1 to 100 ps, and is strongly temperature and excitation density dependent near and below the Néel temperature. While the phase transition is clearly resolved, the anomalously slow dynamics extends far above the transition temperature. Finally, a structural transition with clear hysteresis was observed around 100 K, wit yet minor effect on carrier/spin relaxation dynamics.