Gauge approach to the specific heat in the normal state of cuprates

Many experimental features of the electronic specific heat and entropy of high-Tc cuprates in the normal state, including the nontrivial temperature dependence of the specific-heat coefficient γ and the negative intercept of the extrapolated entropy to T=0 for underdoped cuprates, are reproduced using the spin-charge gauge approach to the t-J model. The entropy turns out to be basically due to fermionic excitations but with a temperature dependence of the specific-heat coefficient controlled by fluctuations of a gauge field coupling them to gapful bosonic excitations. In particular the negative intercept of the extrapolated entropy at T=0 in the pseudogap “phase” is attributed to the scalar component of the gauge field, which implements the local no-double occupancy constraint.