Topography of Spin Liquids on a Triangular Lattice

Abstract

Spin systems with frustrated anisotropic interactions are of significant interest due to possible exotic ground states. We have explored their phase diagram on a nearest-neighbor triangular lattice using the density-matrix renormalization group and mapped out the topography of the region that can harbor a spin liquid. We find that this spin-liquid phase is continuously connected to a previously discovered spin-liquid phase of the isotropic J_{1}-J_{2} model. The two limits show nearly identical spin correlations, making the case that their respective spin liquids are isomorphic to each other.

Hierarchy of Exchange Interactions in the Triangular-Lattice Spin Liquid YbMgGaO4

“…Because of their nonspin-conserving nature, dominant pseudodipolar interactions should manifest as an asymptotic approach to saturated magnetization, as recently observed in the candidate Kitaev spin liquid α-RuCl 3 [81]. Finally, we note that the role and extent of CEF and exchange disorder remains an outstanding issue in YbMgGaO 4 with possible impact ranging from the mimicry of a spin liquid [47,48,82,83] to disorder-induced entanglement [84][85][86].…”

“…We note, however, that subleading pseudodipolar interactions are also necessary to best explain our data. When combined with the likely presence of exchange disorder due to Mg 2þ and Ga 3þ disorder, this makes the spin-liquid mimicry [47,48,82] or the J 1 − J 2 quantum spin-liquid [36][37][38] mechanisms serious contenders to the various scenarios proposed to explain the physics of YbMgGaO 4 thus far [44,62,63].…”

“…Experiments on various spin-S triangular-lattice antiferromagnets have overwhelmingly confirmed this picture [27][28][29][30], with a few noteworthy exceptions [31][32][33]. Several perturbations from the pure TLHAF have been proposed to enhance quantum fluctuations: next-nearest neighbor (NNN) interactions [34][35][36][37][38], ring-exchange terms [39,40], and anisotropic exchange [41][42][43][44], although it remains theoretically unclear if the latter mechanism alone can stabilize a QSL [45][46][47][48]. Nevertheless, anisotropic exchange interactions [49,50] are known to generate new physics in rare-earth pyrochlores such as Yb 2 Ti 2 O 7 [49,[51][52][53], making it worthwhile to investigate their effect in other lattice geometries.…”

“…Additionally, the disordered occupancy of the intertriangular layers by Mg 2þ and Ga 3þ ions [54] appears to affect profoundly the Yb 3þ ions with broadened crystal electric-field (CEF) levels [61,64], a distribution of g tensors [64], and a broadened magnetic excitation spectrum at high fields [61]. The impact of disorder on the YbMgGaO 4 exchange Hamiltonian and, therefore, whether the ground state is a QSL or not, remains an outstanding issue [47,48]. In fact, the nature of the dominant exchange interactions in YbMgGaO 4 is also controversial.…”

YbMgGaO4: A Triangular‐Lattice Quantum Spin Liquid Candidate

“…First of all, the observed QSL GS or at least the quantum disordered behaviors of YbMgGaO 4 have to be understood. The first important ingredient is the anisotropy of the effective spin‐1/2 Hamiltonian caused by the strong spin–orbit entanglement of Yb 3+ , which makes the system localize around the phase boundary between the 120 o and two stripe collinear Néel states, and makes the order very fragile against the quantum fluctuations . While the observed GS properties may be hard to be fully understood by only considering the NN anisotropic (in the spin space) spin Hamiltonian .…”