Condensed Matter Seminar Vitual https://bluejeans.com/410276800/1536
September 15, 2021 - 2:00pm to 3:00pm
Vitual - https://bluejeans.com/410276800/1536
Shanghai Jiaotong University, Department of Physics and Astronomy
Investigating the exotic quantum phenomena and the related ground state of the frustrated quantum magnets has caught a lot of attention over the past years .While the realization of quantum spin liquid (QSL) without conventional magnetic ordering even down to zero temperature is a challenging task, the Kitaev model is a prominent example with an exactly solvable spin model. The Kitaev materails so far have been focused on 4d/5d based systems with effective spin-1/2, such as H3LiIr2O6, α-Li2IrO3, α-Na2IrO3, and α-RuCl3, which exhibit zigzag antiferromagnetic (AFM) ordering at zero magnetic field owing to non-Kitaev interactions such as Heisenberg exchange or off-diagonal exchanges. Recently, the theoretical studies propose that the 3d-cobalt honeycomb magnets with effective spin-1/2 can be another playground to realize the Kitaev model. For example, non-Kitaev terms have been predicted to be almost vanishing with the small trigonal crystal fields acting on Co2+ ions, which makes the cobaltates as one good system for Kitaev physics. We studied the potential candidate Na2Co2TeO6 (NCTO) and performed magnetization, heat capacity, high-field electric spin resonance, and inelastic neutron scattering (INS) measurements. A complicated magnetic field-temperature phase diagram was demonstrated with a zigzag AFM state and spin gap was observed in the spin dynamics. A quantum spin disordered state is induced by an ab-plane magnetic field between ~ 7.5 and 10.5 T like the field-induced QSL in α-RuCl3. Through detailed theoretical simulations on the INS spin-wave spectrum, we could obtain different ratios of the Kitaev interaction and the Heisenberg exchange. Hence, we anticipate our work will generate significant interest: it will trigger new experimental efforts for other realizations of magnetic field inducing the exotic quantum states and rejuvenate theoretical and computational efforts to understand the elusive dynamics in the Kitaev model for frustrated quantum magnetism.