Spin excitation spectrum in strong disorder spin system using spectrum bifurcation renormalization group

Recently the interplay between frustration and disorder has attracted much attention. In the experiment, there is hint that YbMgGaO4 is related to a quantum spin liquid state with a spinon Fermi surface. However, it is still under debate that whether the observed spin-excitation spectrum of YbMgGaO4 is due to effect of spin liquid or disorder. We developed a numerical tool called spectrum bifurcation renormalization group(SBRG) to study strong disordered quantum magnet. Using SBRG, we calculated the spin excitation spectrum of a strong disorder spin model on triangle lattice. We found the spin excitation spectrum agrees well with the experiment, and the result is robust with respect to model parameters.