Evolution of the structural transition in Mo${}_{1-x}$W${}_x$Te${}_2$

Abstract

The composition dependence of the structural transition between the monoclinic 1T${}^{\prime }$ and orthorhombic T${}_d$ phases in the Mo${}_{1-x}$W${}_x$Te${}_2$ Weyl semimetal was investigated by elastic neutron scattering on single crystals up to $x\approx 0.54$. First observed in MoTe${}_2$, the transition from T${}_d$ to 1T${}^{\prime }$ is accompanied by an intermediate pseudo-orthorhombic phase, T${}_d^{\ast }$. Upon doping with W, the T${}_d^{\ast }$ phase vanishes by $x\approx 0.34$. Above this concentration, a phase coexistence behavior with both T${}_d$ and 1T${}^{\prime }$ is observed instead. The interlayer in-plane positioning parameter $\hat{I}´$, which relates to the 1T${}^{\prime }$ ${\hat{I}}^2$ angle, decreases with temperature as well as with W substitution, likely due to strong anharmonicity in the interlayer interactions. The temperature width of the phase coexistence remains almost constant up to $x\approx 0.54$, in contrast to the broadening reported under pressure.

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