Influence of Ti doping on the incommensurate charge density wave in 1T-TaS2

TL;DR

This study investigates how Ti doping affects the charge density wave phases in 1T-TaS2, revealing that Ti influences the CDW orientation and phase coexistence without significantly changing the wave vector magnitude.

Contribution

It provides new insights into the effects of Ti doping on CDW orientation, phase coexistence, and lattice pinning in 1T-TaS2, emphasizing the role of commensuration effects.

Findings

Ti doping rotates the CDW in the basal plane.

Extended coexistence region of IC and NC phases due to Ti.

Resistive anomaly explained by CDW pinning on the lattice.

Abstract

We report temperature-dependent transport and x-ray diffraction measurements of the influence of Ti hole doping on the charge density wave (CDW) in 1T-Ta(1-x)Ti(x)S(2). Confirming past studies, we find that even trace impurities eliminate the low-temperature commensurate (C) phase in this system. Surprisingly, the magnitude of the in-plane component of the CDW wave vector in the nearly commensurate (NC) phase does not change significantly with Ti concentration, as might be expected from a changing Fermi surface volume. Instead, the angle of the CDW in the basal plane rotates, from 11.9 deg at x=0 to 16.4 deg at x=0.12. Ti substitution also leads to an extended region of coexistence between incommensurate (IC) and NC phases, indicating heterogeneous nucleation near the transition. Finally, we explain a resistive anomaly originally observed by DiSalvo [F. J. DiSalvo, et al., Phys. Rev. B {\bf 12}, 2220 (1975)] as arising from pinning of the CDW on the crystal lattice. Our study highlights the importance of commensuration effects in the NC phase, particularly at x ~ 0.08.