Defect and interlayer coupling tuned quasiparticle scattering in 2D disordered Mo₂C superconducting microcrystals

Abstract

Recently, two-dimensional (2D) materials have exhibited many exotic properties, such as topological bands, superconductivity, etc. Among these intriguing systems, interface engineering plays a critical role in inducing, manipulating and even enhancing the properties. Our scanning tunneling microscopic/spectroscopic (STM/S) analysis of 2D superconducting thin α-Mo2C crystal has previously revealed the enhanced TC = 8.02 K originating from the lattice defects. With the same TC, here we demonstrate that the scattering mechanism leads to a more consistent picture to understand the superconductivity in a defected crystal, which can be tuned by interlayer coupling. Using a low-temperature STM, dI/dV spectra were fitted with the Dynes formula to extract the quasiparticle scattering rates at various temperatures. Moreover, the STS analysis of defective sample surfaces and terraces reveals that both quasiparticle scattering rates and zero-bias conductance oscillate as a result of interlayer coupling variation. A temperature-dependent model considering elastic, electron–electron, and electron–phonon inelastic scattering rates was used to fit excellently the quasiparticle scattering rates measured along defects and terraces. The electron–electron scattering rate exhibits a negative fitting parameter, indicating the loss of inelastic electron–electron scattering rate. Additionally, the elastic scattering rate is much higher than the total inelastic scattering rate, which is an indication of the retarded quasiparticle interactions with impurities.