Band dependence of charge density wave and evidence for strong spin-orbit interaction in quasi-one-dimensional Ta₂NiSe₇

Low-dimensional materials featuring charge density wave (CDW) provide opportunities for studying the effect of electron-electron interactions that depend strongly on the dimensionality. Quasi-one-dimensional transition-metal chalcogenide Ta₂NiSe₇, which crystallized in a layered monoclinic structure with ab basal plane and Ta and Ni chains along the b direction, was found to show interesting magnetoresistance (MR) originating from band dependent CDWs [1]. In this experiment, we explored further the field and field orientation dependence of MR and found a clear change in in the curvature of MR curve as a function of the field. More importantly, the magnetic field orientation dependence of MR shows a striking change of the symmetry axis below CDW transition only for a rotating magnetic field in the ac plane and current along b direction. In this configuration (H in ac plane), the symmetry axis rotates progressively when entering the CDW state and continues to rotate all the way to the lowest temperature by around 25 degrees, while for other configurations (H in bc and ab plane) the symmetry axis remains unchanged. We argue that the rotation of symmetry axis is an evidence for strong spin-orbit interaction in this system.

[1] J. He et al., Appl. Phys. Lett. 111, 052405 (2017).