Anisotropic exchange coupling and ground state phase diagram of Kitaev compound YbOCl

Abstract

Rare-earth chalcohalide REChX (RE = rare earth; Ch = O, S, Se, Te; X = F, Cl, Br, I) is a newly reported family of Kitaev spin liquid candidates. The family offers a platform where a strong spin-orbit coupling meets a van der Waals layered and undistorted honeycomb spin lattice, which outputs highly anisotropic exchange couplings required by the Kitaev model. YbOCl is the first single crystal of the family we grew, with a size up to ∼15 mm. We have performed magnetization and high magnetic field electron spin resonance measurements from 2 to 300 K. We develop the mean-field scenario for the anisotropic spin system, with which we are able to well describe the experiments and reliably determine the fundamental parameters. The self-consistent simulations give the anisotropic spin-exchange interactions of J ± (∼ − 0.3 K) and J zz (∼1.6 K), and g factors of g ab (∼3.4) and g c (∼2.9). Based on the spin-exchange interactions, we employ the exact diagonalization method to work out the ground state phase diagram of YbOCl in terms of the off-diagonal exchange couplings. The phase diagram hosting rich magnetic phases including the spin-disordered one, sheds light on the novel magnetic properties of the family, particularly the Kitaev physics.

Magnetic Phase Diagram of van der Waals Antiferromagnet TbTe3

“…YbOCl has been investigated numerically in this respect, evidencing an exclusively rich magnetic phase diagram in terms of anisotropic exchange interactions J ± and J zz . Along with Neel, collinear, stripy, zigzag, and 120-AFM phases, this diagram hosts the spin-disordered one related presumably to the Kitaev physics [3].…”

Ba9RE2(SiO4)6 (RE = Ho–Yb): A Family of Rare-Earth-Based Honeycomb-Lattice Magnets

“…13,16 Compared to the 4d/5d-based Mott insulators, the 4f electron systems can also exhibit the Kitaev-type interactions stabilized by strong SOC and dedicate exchange pathways in the edge-sharing honeycomb network, 16−18 but that is less experimentally studied for investigating the Kitaev quantum spin liquid physics. Another difference is that the exchange interactions between RE 3+ local moments are relatively small, which let us safely consider the dominance of nearest-neighbor 18,31 Unfortunately, the experimental identification on Kitaev QSL states remains to be challenging since most discovered RE-based Kitaev materials form a magnetic ordered phase at low temperatures. For example, the relatively well-studied YbCl 3 exhibits a short-range magnetic order below 1.20 K and long-range AFM order with a Neél temperature T N of ∼0.60 K, 24 and Na 2 PrO 3 enters into the AFM state below a T N of ∼4.6 K. 25 From the structural viewpoint, magnetic RE ions in most RE-based honeycomb magnets including YbCl 3 , Yb 2 Si 2 O 7 , and Na 2 PrO 3 are arranged on a distorted honeycomb lattice not a perfect honeycomb lattice, 24,26,27 which may introduce additional anisotropic exchange interactions precluding the formation of the Kitaev QSL state.…”

“…The search for Kitaev QSL states in real materials has been extensively performed on the honeycomb-lattice magnets comprising the 4d/5d transition-metal ions due to the bond-dependent interactions inherent to the strong SOC. , Also, several efforts have been made to find other candidate materials; along this direction, materials exploration is extended to the systems containing 4f rare-earth (RE) ions. , Compared to the 4d/5d-based Mott insulators, the 4f electron systems can also exhibit the Kitaev-type interactions stabilized by strong SOC and dedicate exchange pathways in the edge-sharing honeycomb network, − but that is less experimentally studied for investigating the Kitaev quantum spin liquid physics. Another difference is that the exchange interactions between RE 3+ local moments are relatively small, which let us safely consider the dominance of nearest-neighbor spin interactions and easily realize the field-tuned QSL phase at a low field accessible in the laboratory. − Very recently, several studies have been conducted on the RE-based Kitaev candidates with different 4f electron configurations including trichlorides YbX 3 (X = F, Cl, Br, and I), − A 2 REO 3 (A = Li and Na; RE = Pr and Tb) , and RE 2 Si 2 O 7 (RE = Er–Yb) oxides, − and chalcohalides REChX (Ch = O, S, Se, and Te, X = F, Cl, Br, I). , Unfortunately, the experimental identification on Kitaev QSL states remains to be challenging since most discovered RE-based Kitaev materials form a magnetic ordered phase at low temperatures. For example, the relatively well-studied YbCl 3 exhibits a short-range magnetic order below 1.20 K and long-range AFM order with a Néel temperature T N of ∼0.60 K, and Na 2 PrO 3 enters into the AFM state below a T N of ∼4.6 K .…”

Disordered ground state in the spin-orbit coupled Jeff = 12 distorted honeycomb magnet BiYbGeO5

“…The anisotropic nature of the ion itself, as well as exchange anisotropy of magnetic couplings, may be behind many interesting effects, including the possible realization of quantum spin ice in pyrochlore materials [10][11][12], persistent dynamics observed in triangular spin-liquid candidates [13,14], and Tomonaga-Luttinger liquid behavior with spinon confinement-deconfinement transitions in spin-chain magnets [15]. Yb-based honeycomb magnets are currently studied * rnath@iisertvm.ac.in as potential hosts for Kitaev physics [16][17][18][19]. Concurrently, deformed honeycomb lattices of Yb 3+ could provide an interesting link to Yb 2 Si 2 O 7 and reveal the effect of magnetic anisotropy on the field-induced states of a dimer magnet.…”