Distinct superconducting properties and hydrostatic pressure effects in 2D α- and β-Mo2C crystal sheets

Abstract

Abstract Recently, 2D Mo 2 C, a new member of the MXene family, has attracted much attention due to the exotic superconducting properties discovered in 2D α -Mo 2 C. Here, not only 2D α -Mo 2 C but also 2D β -Mo 2 C crystal sheets with distinct disordered carbon distributions were successfully grown. 2D β -Mo 2 C shows a much stronger superconductivity than 2D α -Mo 2 C, and their superconductivities have different hydrostatic pressure responses. The superconducting transition temperature T c of 2D α -Mo 2 C shows a dome-shaped profile under pressure, implying the existence of two competing effects arising from phononic and electronic properties, while for 2D β -Mo 2 C, T c decreases monotonically with increasing pressure, possibly due to phonon stiffening. These results indicate that the electronic properties have a more important influence on the superconductivity in 2D α -Mo 2 C compared to 2D β -Mo 2 C. The ordered and disordered carbon distributions in 2D α -Mo 2 C and β -Mo 2 C, respectively, may be the underlying origin for their different electronic and superconducting properties.