Transition to Temperature Chaos in Spin Glasses

The concept of temperature chaos (TC) in spin glasses has been a controversial issue. Recently, two independent observations of TC have been reported^1,2 along with justification of its existence in off-equilibrium spin glass dynamics.³ A remaining issue is the nature of the onset of TC as the temperature change, ΔT, passes from reversible to chaotic, appearing narrower in experiment as compared to simulations. We invoke a temperature cycling protocol to determine the nature and width of the transition. The coherence length, ξ₀(T₁ ,t_w1), is extracted at an initial temperature T₁ after aging t_w1. The temperature is reduced by ΔT_R within the reversible range and held for t_w2 (t_w2 > t_w1). It is then raised back to T₁ and the coherence length ξ_R(T₁) measured. A separate experiment replicates the first step, but lowers the temperature by ΔT_C to reach the chaotic regime (ΔT_C > ΔT_R). The system is aged t_w2, then heated back to T₁ and ξ_C(T₁) measured. Validation of reversibility and chaoticity: ξ_C(T₁) < ξ₀(T₁) < ξ_R(T₁) enables the determination of the temperature width of the transition to chaos. Results on single crystals of CuMn will be reported.