  Doping tin surface epitaxially grown on silicon, Sn/Si(111), with boron atoms
yields the appearance of a superconducting (SC) phase below $T_c\sim 4-5$K.
Even though the pairing mechanism remains unknown, experimental evidence of
chiral $d-$wave superconductivity has been recently reported, then ruling out a
phonon-mediated pairing. Here we study theoretically the SC phase and
symmetries of the doped Sn/Si(111) within a $t-J$ model. We analyze the
photo-excitation of the system by intense THz pulses and show that the
polarization dependence of the induced current can distinguish between
different symmetries of the SC gap, thus providing a novel experimental mean to
investigate the spectroscopic features of the Sn/Si(111) across the SC
transition.
