Magnetic anisotropy in 1T-TaS₂

Belonging to the family of transition metal dichalcogenides, 1T-TaS₂ has attracted significant attention for more than 40 years thanks to its extremely rich phase diagram, which results from significant electron-electron interactions. The material undergoes a series of charge-density wave transitions upon cooling before reaching a completely commensurate (CCDW) state at ~ 200K. The CCDW state is believed to be a Mott insulator -- albeit unaccompanied by magnetic order or even any sign of a local magnetic moment -- and has been dubbed a quantum spin liquid (QSL).

We report preliminary results of the magnetotropic coefficient of 1T-TaS₂ -- the second derivative of the free energy with respect to the applied magnetic field angle [1- 2]. Our results show a very clear out-of-plane magnetic anisotropy in 1T-TaS₂ as a function of the applied magnetic field and temperature within the CCDW state. At the lowest temperatures, the results show a crossover from isotropic behavior at low field (up to ~6 T) to an anisotropic state at higher fields. Increasing temperature suppresses the magnetic field needed to observe the anisotropic response. These measurements at higher temperatures will help resolve whether the extremely weak magnetic response in 1T-TaS₂ [1-2]is due to impurity spins, spin dimerization, or the emergence of a quantum spin liquid.



References:

[1] Modic, K.A., Bachmann, M.D., Ramshaw, B.J. et al. Resonant torsion magnetometry in anisotropic quantum materials. Nat Commun 9, 3975 (2018)

[2] Shekhter, A., et al. "The magnetotropic susceptibility." arXiv preprint arXiv:2208.10038 (2022).