From domain walls and the stripe phase to full suppression of charge density wave in the superconducting 1T-Ti$_{1-\text{x}}$Ta$_\text{x}$Se$_2$

TL;DR

This study explores how Ta substitution in 1T-TiSe2 affects charge density waves and superconductivity, revealing complex domain structures, symmetry-breaking stripes, and the suppression of CDW with the emergence of superconductivity.

Contribution

It provides a detailed phase diagram of 1T-Ti$_{1-x}$Ta$_x$Se$_2$ showing the evolution from CDW to superconductivity over a wide doping range.

Findings

Identification of two types of domain walls with atomic resolution.

Discovery of a symmetry-breaking stripe CDW at light doping.

Superconductivity observed despite the collapse of the CDW at high doping.

Abstract

1T-TiSe$_2$ hosts a $2 \times 2 \times 2$ charge density wave (CDW) that is known to form the state with localized domains separated by the domain walls upon Cu intercalation. The CDW state with the domain wall network has attracted significant interest due to its coexistence with superconductivity. Here we present a scanning tunneling microscopy, transport and magnetic susceptibility study of 1T-Ti$_{1-\text{x}}$Ta$_\text{x}$Se$_2$. Ta substitution for Ti atoms allows us to perform experiments over the wide range of doping ($ 0 \leqslant \text{x} \leqslant 0.2$), providing access to a significantly broader phase diagram than Cu intercalation experiments. At x = 0.02, we observe a complex network of domains and domain walls. We identify two distinct types of domain walls and show their structure with atomic resolution. Additionally, an elusive symmetry-breaking stripe CDW is found at the light substitution of x = 0.02. We also measure highly substituted x = 0.2 crystals that are superconducting despite the full collapse of the CDW order. Our results uncover rich CDW physics in Ta-substituted 1T-TiSe2 crystals and illuminate the interplay between the CDW and superconductivity.