Investigation of the Superconducting Gap inLa2−xSrxCuO4by Raman Spectroscopy

The low energy Raman spectra of a ${\mathrm{La}}_{1.83}$ ${\mathrm{Sr}}_{.17}$Cu${\mathrm{O}}_4$ single crystal have been measured at temperatures above and below $T_c$. The redistribution of the electronic continua that occurs as a result of the opening of the superconducting gap has been observed. Based on the polarization dependence of the continua, it is concluded that the superconducting gap $\Delta \left(\mathbf{k}\right)$ is anisotropic, with nodes along the (±1, ±1) directions and maxima along the (0, ±1) and (±1, 0) directions. The maximum pairing energy $2\left|{\Delta }_{max}\right|$ is estimated to be about $7.7k{T}_c$.