Probing the quantum phase transition in Mott insulator BaCoS_2 tuned by pressure and Ni-substitution

Z. Guguchia; B. A. Frandsen; D. Santos-Cottin; S. C. Cheung; Z. Gong; Q. Sheng; K. Yamakawa; A. M. Hallas; M. N. Wilson; Y. Cai; J. Beare; R. Khasanov; R. De Renzi; G. M. Luke; S. Shamoto; A. Gauzzi; Y. Klein; Y. J. Uemura

doi:10.1103/physrevmaterials.3.045001

arXiv · 1901.07802

Probing the quantum phase transition in Mott insulator BaCoS_2 tuned by pressure and Ni-substitution

Z. Guguchia·B. A. Frandsen·D. Santos-Cottin·S. C. Cheung·Z. Gong·Q. Sheng·K. Yamakawa·A. M. Hallas·M. N. Wilson·Y. Cai·J. Beare·R. Khasanov·R. De Renzi·G. M. Luke·S. Shamoto·A. Gauzzi·Y. Klein·Y. J. Uemura

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Abstract

We present a muon spin relaxation study of the Mott transition in BaCoS_2 using two independent control parameters: (i) pressure p to tune the electronic bandwidth and (ii) Ni-substitution x on the Co site to tune the band filling. For both tuning parameters, the antiferromagnetic insulating state first transitions to an antiferromagnetic metal and finally to a paramagnetic metal without undergoing any structural phase transition. BaCoS_2 under pressure displays minimal change in the ordered magnetic moment S_ord until it collapses abruptly upon entering the antiferromagnetic metallic state at p_cr ~ 1.3 GPa. In contrast, S_ord in the Ni-doped system Ba(Co_{1-x}Ni_{x})S_{2} steadily decreases with increasing x until the antiferromagnetic metallic region is reached at x_cr ~ 0.22. In both cases, significant phase separation between magnetic and nonmagnetic regions develops when approaching p_cr or x_cr, and the antiferromagnetic metallic state is characterized by weak, random, static magnetism in a small volume fraction. No dynamical critical behavior is observed near the transition for either tuning parameter. These results demonstrate that the quantum evolution of both the bandwidth- and filling-controlled metal-insulator transition at zero temperature proceeds as a first-order transition. This behavior is common to magnetic Mott transitions in RENiO_3 and V_2O_3, which are accompanied by structural transitions without the formation of an antiferromagnetic metal phase.

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Z. Guguchia, B. A. Frandsen, D. Santos-Cottin, S. C. Cheung, Z. Gong, Q. Sheng, K. Yamakawa, A. M. Hallas, M. N. Wilson, Y. Cai, J. Beare, R. Khasanov, R. De Renzi, G. M. Luke, S. Shamoto, A. Gauzzi, Y. Klein, Y. J. Uemura. 2019-01-23. Probing the quantum phase transition in Mott insulator BaCoS_2 tuned by pressure and Ni-substitution. https://doi.org/10.1103/physrevmaterials.3.045001

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