Strongly correlated spin liquid in herbertsmithite

Exotic strongly correlated quantum spin liquid (SCQSL) is formed in an insulator Herbertsmithite ZnCu3(OH)6Cl2 with such hypothetic particles as fermionic spinons carrying spin 1=2 and no charge. Here we calculate its thermodynamic and relaxation properties. Our calculations unveil the fundamental properties of SCQSL, forming strongly correlated Fermi system located at a fermion condensation quantum phase transition. These are in good agreement with experimental data and allow us to detect the behavior of SCQSL as that observed in heavy fermion metals and 2D 3He. We predict that the thermal resistivity of SCQSL under the application of magnetic fields at fixed temperature demonstrates a very specific behavior. The key features of our findings are the presence of spin-charge separation and QSL formed with itinerant heavy spinons in herbertsmithite.