  Strongly correlated Fermi systems are among the most intriguing and
fundamental systems in physics, whose realization in some compounds is still to
be discovered. We show that herbertsmithite ZnCu_3(OH)_6Cl_2 can be viewed as a
strongly correlated Fermi system whose low temperature thermodynamic in
magnetic fields is defined by a quantum critical spin liquid. Our calculations
of its thermodynamic properties are in good agreement with recent experimental
facts and allow us to reveal their scaling behavior which strongly resembles
that observed in HF metals and 2D 3He.
