Effect of phase fluctuations on the single-particle properties of underdoped cuprates

We study the effect of order parameter phase fluctuations on the single-par ticle properties of fermions in the underdoped cuprate superconductors usin g a phenomenological low-energy theory. We identify the fermion-phase field coupling as the Doppler shift of the quasiparticle spectrum induced by the fluctuating superfluid velocity and we calculate the effect of these fluct uations on the fermion self-energy. We show that the vortex pair unbinding near the superconducting transition causes a significant broadening in the fermion spectral function, producing a pseudogaplike feature. We also discu ss the specific heat and show that the phase fluctuation effect is visible due to the short coherence length. [S0163-1829(99)05209-1].