Anticorrelation between polar lattice instability and superconductivity in the Weyl semimetal candidate MoTe_2

摘要

The relation between the polar structural instability and superconductivity in a Weyl semimetal candidateMoTe2 has been clarified by finely controlled physical and chemical pressure. The physical pressure as wellas the chemical pressure, i.e., the Se substitution for Te, enhances the superconducting transition temperatureTc at around the critical pressure where the polar structure transition disappears. From the heat capacity andthermopower measurements, we ascribe the significant enhancement of T_c at the critical pressure to a subtlemodification of the phonon dispersion or the semimetallic band structure upon the polar-to-nonpolar transition.On the other hand, the physical pressure, which strongly reduces the interlayer distance, is more effective on thesuppression of the polar structural transition and the enhancement of T_c as compared with the chemical pressure,which emphasizes the importance of the interlayer coupling on the structural and superconducting instability inMoTe_2.