Fig. 1
From: Tuning high-Q nonlinear dynamics in a disordered quantum magnet
Schematic of spin configuration and transition pathways in pumped LiHo0.045Y0.955F4. a Tightly bound spin clusters embedded in a dilute spin bath. Closely separated spins form a tightly bound cluster, which can be magnetized in a nonlinear response regime by a strong ac pump field. Spatially adjacent clusters can interact directly. b Schematic of cluster excitation pathways. Clusters of different sizes have different energy gaps, so the choice of pump frequency acts as a size selector. Direct interactions between excited clusters and off-resonance clusters give rise to Fano resonance behavior. c Magnetization amplitude (top) and phase angle (bottom) for three different excitation frequencies. d Pump-probe measurements (ratios of imaginary part of response χ'' in presence of pump to response χ''0 without pump) in two thermodynamic regimes. When LiHo0.045Y0.955F4 is weakly coupled to an external heat reservoir, the low-temperature state is dominated by the quantum cluster response, giving rise to strong Fano resonances. When it is strongly coupled to an external heat reservoir, it exhibits extended glassy behavior including the absence of hole-burning and Fano resonance effects25. Both traces were measured at T = 100 mK, fpump = 20 Hz, and hpump = 0.5 Oe
