Scaling in dynamic susceptibility of herbertsmithite and heavy-fermion metals

We present a theory of the dynamic magnetic susceptibility of quantum spin liquid. The obtained results are in good agreement with experimental facts collected on herbertsmithite ZnCu3(OH)6Cl2ZnCu3(OH)6Cl2 and on heavy-fermion metals, and allow us to predict a new scaling in magnetic fields in the dynamic susceptibility. Under the application of strong magnetic fields quantum spin liquid becomes completely polarized. We show that this polarization can be viewed as a manifestation of gapped excitations when investigating the spin-lattice relaxation rate.

► We present a theory of the dynamic magnetic susceptibility of quantum spin liquid. ► We calculate the dynamic susceptibility of ZnCu3(OH)6Cl2 as a function of temperature versus energy. ► Our calculations are in good agreement with experimental facts. ► We explain the scaling of the dynamic susceptibility and predict a new scaling in magnetic fields. ► The polarization in magnetic fields can be viewed as a manifestation of gapped excitations.