Effects of doping on thermally excited quasiparticles in the high-T-c superconducting state

The physical properties of low-energy superconducting quasiparticles in high-T-c superconductors are examined using magnetic penetration depth and specific-heat experimental data. We find that the low-energy density of states of quasiparticles of La2-xSrxCuO4 scales with (x-x(c))/T-c to the leading-order approximation, where x(c) is the critical doping concentration below which T-c=0. The linear temperature term of the superfluid density is renormalized by quasiparticle interactions and the renormalization factor times the Fermi velocity is found to be doping independent.