Fully gapped type-II superconductivity in Pt-doped IrTe2 near critical doping

Abstract

The Dirac point in Pt-doped ${\mathrm{IrTe}}_{2}$ is known to be tuned by controlling the doping concentration. For 10% Pt, it is seen that the Dirac point exists close to the Fermi energy of the system. This leads to the expectation that, for such doping, the system might host unconventional (topological) superconductivity. Here, we present a detailed microscopic and spectroscopic investigation of $\mathrm{Pt}\text{\ensuremath{-}}{\mathrm{IrTe}}_{2}$ under an ultrahigh vacuum, low-temperature scanning tunneling microscope. We find that, for the crystals of ${\mathrm{Ir}}_{0}{.}_{9}{\mathrm{Pt}}_{0}{.}_{1}{\mathrm{Te}}_{2}$, the surface shows patches of atomic scale over which defects are seen to be randomly distributed. Tunneling spectroscopy reveals that ${\mathrm{Ir}}_{0}{.}_{9}{\mathrm{Pt}}_{0}{.}_{1}{\mathrm{Te}}_{2}$ condenses into a fully gapped Bardeen-Cooper-Schrieffer-like (BCS) $s$-wave superconducting state. The superconducting gap was measured to be $460\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{eV}$ at 310 mK. The value of $2{\mathrm{\ensuremath{\Delta}}}_{0}/{k}_{B}{T}_{c}\ensuremath{\sim}6$ is consistent with a conventional BCS superconductor in the strong-coupling limit. The conventional behavior is surprising, given the topological band structure of the material.