Rare-Earth Chalcohalides: A Family of van der Waals Layered Kitaev Spin Liquid Candidates

Abstract

The Kitaev spin liquid (KSL) system has attracted tremendous attention in recent years because of its fundamental significance in condensed matter physics and promising applications in fault-tolerant topological quantum computation. Material realization of such a system remains a major challenge in the field due to the unusual configuration of anisotropic spin interactions, though great effort has been made before. Here we reveal that rare-earth chalcohalides REChX (RE = rare earth; Ch = O, S, Se, Te; X = F, Cl, Br, I) can serve as a family of KSL candidates. Most family members have the typical SmSI-type structure with a high symmetry of R 3 ¯ m , and rare-earth magnetic ions form an undistorted honeycomb lattice. The strong spin-orbit coupling of 4f electrons intrinsically offers anisotropic spin interactions as required by the Kitaev model. We have grown the crystals of YbOCl and synthesized the polycrystals of SmSI, ErOF, HoOF and DyOF, and made careful structural characterizations. We carry out magnetic and heat capacity measurements down to 1.8 K and find no obvious magnetic transition in all the samples but DyOF. The van der Waals interlayer coupling highlights the true two-dimensionality of the family which is vital for the exact realization of Abelian/non-Abelian anyons, and the graphene-like feature will be a prominent advantage for developing miniaturized devices. The family is expected to act as an inspiring material platform for the exploration of KSL physics.

The Role of the Third Dimension in Searching Majorana Fermions in $α$-RuCl$_3$ via Phonons

“…Our findings also indicate that the renormalization of the phonons due to Majorana fermions [63][64][65][66] is enhanced for the phonons with their momenta or polarization in the out-of-plane direction, and that it could therefore be sensitive to the stacking structure of the crystals. These conclusions on the role of the third dimension in the search of Majorana fermions via phonons are relevant not only for α-RuCl 3 , but for van der Waals based Kitaev candidate materials in general [67][68][69], a class of materials that offer the potential of heterostructure engineered Kitaev quantum spin liquids, and true two-dimensionality via exfoliation.…”

DyOCl: a rare-earth based two-dimensional van der Waals material with strong magnetic anisotropy

“…1(a)] [36]. Its crystal structure is different from YbOCl, which has a SmSI-type structure with honeycomb lattice [24]. This crystal structure is confirmed by Xray analysis of both powders diffraction patterns and 00l relections of single crystal, as presented in Fig.…”

“…A recent study found that GdTe 3 is the first vdW material with both high mobility and magnetism, which might provide potential for new twistronic and spintronic elecntrical applications [22]. Very recently, YbCl 3 [23] and YbOCl [24] were proposed to be Kitaev spin liquid candidates. Besides these reports, the investigation on mag- netic RE vdW materials is still at the early stage.…”

Magnon Condensation in Dimerized Antiferromagnets with Spin-Orbit Coupling

“…Generally, SOC in quantum magnets locks the spin rotation operations with the corresponding lattice rotations and hence reduce the continuous spin rotation symmetries to discrete ones. A class of spin-orbit coupled antiferromagnets on the honeycomb lattice has the discrete symmetry group D 3d [23][24][25][26][27] and contains anisotropic spin-spin interactions in addition to the isotropic Heisenberg exchanges (J terms). The anisotropic interactions include, the diagonal Kitaev type exchange terms S γ i S γ j (K terms) [28][29][30] and the off-diagonal exchange interactions such as the S α i S β j +S β i S α j interactions (Γ terms) 31,32 or the S α i S γ j + S γ i S α j + S β i S γ j + S γ i S β j interactions (Γ terms) [33][34][35][36] , here α, β, γ = x, y, z and we have only listed the interactions on the γ-bond.…”