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TT: Fachverband Tiefe Temperaturen

TT 41: Correlated Electrons: Quantum-Critical Phenomena

TT 41.2: Vortrag

Mittwoch, 22. März 2017, 09:45–10:00, HSZ 204

Critical spin dynamics in YbCo₂Si₂ — A. Hannaske¹, K. Schmalzl², C. Geibel¹, and •O. Stockert¹ — ¹Max-Planck-Institut CPfS, Dresden, Germany — ²JCNS at ILL, Grenoble, France

The strongly correlated compound YbCo₂Si₂ is the antiferromagnetically ordered sister compound to quantum critical YbRh₂Si₂. The magnetic order in YbCo₂Si₂ with T_N = 1.7  K can be continuously suppressed upon application of a magnetic field with a critical field of B_c = 2  T. We performed detailed inelastic neutron scattering experiments on single-crystalline YbCo₂Si₂ to study the spin dynamics at B_c. A critical slowing down of the magnetic response is observed as function of temperature at B_c with slightly sublinear temperature dependence of the relaxation rate of the critical spin fluctuations. Moreover, as inferred from measurements at finite momentum transfer, away from the antiferromagnetic ordering wave vector, the paramagnons soften and their lifetime decreases with temperature. Our results will be compared with theoretical calculations.