Inferring the pairing symmetry of the superconducting Sn/Si(111) via angle-resolved terahertz pump spectroscopy

Doping tin surface epitaxially grown on silicon, Sn/Si(111), with boron atoms yields the appearance of a superconducting (SC) phase below <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:msub> <a:mi>T</a:mi> <a:mi>c</a:mi> </a:msub> <a:mo>∼</a:mo> <a:mn>4</a:mn> <a:mo>−</a:mo> <a:mn>9</a:mn> <a:mspace width="0.28em"/> <a:mi mathvariant="normal">K</a:mi> </a:mrow> </a:math> . Even though the pairing mechanism remains unknown, experimental evidence of chiral <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:mrow> <d:mi>d</d:mi> <d:mo>−</d:mo> <d:mi>wave</d:mi> </d:mrow> </d:math> superconductivity has been recently reported, thus ruling out a phonon-mediated pairing. Here, we study theoretically the SC phase of the doped Sn/Si(111) within a <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mrow> <e:mi>t</e:mi> <e:mo>−</e:mo> <e:mi>J</e:mi> </e:mrow> </e:math> model investigating different symmetries of the order parameter. We analyze the photoexcitation of the system by intense terahertz pulses and show that the polarization dependence of the induced current can distinguish between different symmetries of the SC gap, thus providing an experimental means to investigate the spectroscopic features of the Sn/Si(111), and possibly to many other systems, across the SC transition.