Superconductivity related to local electronic and atomic structures in layered chalcogenide 1T-TaS_2-xSe_x

¹ Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University - Chengdu 610064, China
² Institute of New Energy and Low- Carbon Technology, Sichuan University - Chengdu 610065, China

^(a) rang@scu.edu.cn

Received: 16 July 2019
Accepted: 25 October 2019

Abstract

We have performed temperature-dependent synchrotron radiation x-ray absorption fine structure (XAFS) spectra of layered transition metal dichalcogenide 1T-TaS_2-xSe_x to elucidate the local electronic and atomic structure especially associated with the occurrence of superconductivity for the first time. We observed a corresponding temperature-dependent phase transition from nearly commensurate to commensurate charge density wave, as well as a characteristic of p-d hybridization between Ta 5d and Se 4p states, which is favorable to boost superconductivity, determined by x-ray absorption near edge structure (XANES) spectra at the Ta L₃-edge and Se K-edge, respectively. And also, the periodic lattice distortion accompanied by the occurrence of charge density wave is clearly demonstrated by extended XAFS (EXAFS) spectra at the Ta L₃-edge of the pristine sample 1T-TaS₂, which is clearly suppressed in the Se-doping sample 1T-TaSSe with a maximum transition temperature . The present results reveal that the p-d hybridization and the loss of long-range coherence of the CDW state play an important role in manipulating the superconductivity, shedding new light on the physics mechanism of the interplay between superconductivity, charge order, and electron correlation.