Figure 5: Critical scaling and quantum phase diagram.

(a) Scaling plot of the power-law component of the susceptibility multiplied by the power of temperature χ_cT^γ against a magnetic field divided by temperature H/T. The data for both T≤0.07 K and μ₀H≤1.2 T are excluded from the figure for clarity. The dashed curve shows a scaling function, f(x)=a(x²+b²)^−γ/2, where a and b represent certain constants, and x=(H−H_c)/T^1/νz. Inset: the scaling plot of the data for the a*−b field rotation in the different sample. The s.d., σ, of the scaling for various values of (b) γ and νz, and (c) H_c, when the other two parameters are fixed. (d) Contour plot of χ_cT^0.83 in the T−H plane. The red and blue areas represent the quantum critical (QC) and quantum spin-liquid (QSL) regimes, respectively, which are bounded by the crossover region (yellow area). The scaling is broken in a low temperature and field region (shaded area).