Fig. 6
From: Observing a scale anomaly and a universal quantum phase transition in graphene
Comparison between the experimentally obtained E 2/E 1 ratio and the universal factor \({e^{ - \pi /\sqrt {{\beta ^2} - 1/4} }}\). Blue points: the ratio E 2/E 1 obtained from the position of the points in Fig. 5. Cyan point: Universal Efimov energy ratio as measured in Caesium atoms39, 47. Blue line (dashed): the corresponding optimized curve, fitted according to the model \({e^{ - b/\sqrt {{\beta ^2} - 1/4} }}\) and corresponding to b = 3.145 with standard error of Δb = 0.06 consistent with the predicted value π. The shaded pink region is the ±2Δb confidence interval of the curve. Cyan line: universal low-energy factor \({e^{ - \pi /\sqrt {{\beta ^2} - 1/4} }}\). Purple line: theoretical ratio E 2/E 1 obtained from the exact solution of the Dirac equation. As β → 0.5, |E n | becomes smaller therefore the green and purple curves coincide for low β. The error bar on the resonance energies is ±1 mV
