Abstract
This article introduces the thermodynamic properties of a quantum spin liquid state. In strongly frustrated antiferromagnetic spin systems, there is possibility of a quantum fluctuated ground state called “quantum spin liquid state”. The absence of candidate materials prevents an intrinsic experimental study of spin liquid problem for more than 30 years. However, in this decade, the quantum spin liquid behavior had been observed in two molecule based charge transfer salts, which form dimerized structure in crystal and show Mott insulating behavior at low temperature. Recently, thermodynamic studies succeeded to discover gapless excitation structure in the quantum spin liquid state in two molecule based charge transfer salts. Since accurate heat capacity measurements can estimate absolute values of heat capacity, the quantitative discussion on coefficient γ in heat capacity had also unveiled Fermi liquid character of quantum spin liquid state despite that this state is insulating in terms of conductivity. These thermodynamic observations would promote quantum spin liquid study to new stage.
https://ror.org/035t8zc32 
