Multipolar magnetism in $5d^2$ vacancy-ordered halide double perovskites
| Autor: | Pradhan, Koushik, Paramekanti, Arun, Saha-Dasgupta, Tanusri |
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| Rok vydání: | 2024 |
| Předmět: | |
| Zdroj: | Phys. Rev. B 109, 184416 (2024) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevB.109.184416 |
| Popis: | Vacancy-ordered halide double perovskites hosting 4d/5d transition metals have emerged as a distinct platform for investigating unconventional magnetism arising out of the interplay of strong atomic spin-orbit coupling (SOC) and Coulomb interactions. Focusing on the $d^2$ system Cs$_2$WCl$_6$, our ab initio electronic structure calculation reveals very narrow electronic bands, fulfilling the necessary condition to realize exotic orders. Using this input, we solve the many-body spin-orbit coupled single-site problem by exact diagonalization and show that the multiplet structure of Cs$_2$WCl$_6$ hosts ground non-Kramers doublets on W, with vanishing dipole moment and a small gap to an excited magnetic triplet. Our work provides the rationale for the observed strong deviation from the classic Kotani behaviour in Cs$_2$WCl$_6$ for the measured temperature dependence of the magnetic moment. The non-Kramers doublets on W exhibit non-zero quadrupolar and octupolar moments, and our calculated two-site exchange supports the dominance of inter-site octupolar exchange over quadrupolar interactions. We predict ferro-octupolar order with a transition temperature $T_c \sim 5$K which may get somewhat suppressed by quantum fluctuations and disorder; this could be tested in future low-temperature experiments. Comment: 8 pages, 5 figs, submitted to PRB |
| Databáze: | arXiv |
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