Anisotropic time-domain electronic response in cuprates driven by midinfrared pulses

Superconductivity in the cuprates is characterized by an anisotropic electronic gap of d-wave symmetry. The aim of this work is to understand how this anisotropy affects the nonequilibrium electronic response of high-Tc superconductors. Here we use a polarization selective time domain experiment to address the dynamics of electronic excitation of different symmetry in optimally doped Bi2Sr2Y0.08Ca0.92Cu2O8+? and measure the nodal and antinodal nonequilibrium response resulting from photoexcitations with ultrashort pulses with photon energy comparable to the superconducting gap. The response to long wavelength photoexcitation with pump polarization along the Cu-Cu axis of the sample is discussed with the support of an effective d-wave BCS model which suggests that such transient response could be ascribed to an increase of pair coherence in the antinodal region.