Suppression of stacking order with doping in 1T-TaS$_{2-x}$Se$_x$

TL;DR

This study investigates how selenium doping in 1T-TaS$_{2-x}$Se$_x$ affects the stacking order and charge density wave states, revealing suppression of certain stacking sequences and a transition to a nearly commensurate state.

Contribution

It provides the first neutron scattering comparison of stacking order changes due to Se doping in 1T-TaS$_2$, linking doping to suppression of specific layer stacking and CDW states.

Findings

Doping with Se suppresses the 13c layer stacking order.

Se doping leads to a nearly commensurate state with the Mott state suppressed.

Layer stacking order is absent in Se-doped samples, unlike in pure TaS$_2$.

Abstract

In 1T-TaS$_{2-x}$Se$_x$, the charge density wave (CDW) state features a star of David lattice that expands across layers as the system becomes commensurate on cooling. The layers can also order along the c-axis and different stacking orders have been proposed. Using neutron scattering on powder samples, we compared the stacking order previously observed in 1T-TaS$_2$ as the system is doped with Se. While at low temperature, a 13c layer sequence stacking was observed in TaS$_2$, this type of ordering was not evident with doping. Doping with Se results in a nearly commensurate state with the Mott state suppressed which may be linked to the absence of the layer stacking.