Symmetry-protected non-Fermi liquids, kagome spin liquids, and the chiral Kondo lattice model

Abstract

The theoretical description of non-Fermi liquids is among the most challenging questions in strongly correlated quantum matter. While there are many experimental candidates for such phases, few examples can be studied using controlled theoretical approaches. Here we introduce a novel conceptual perspective to analytically describe the non-Fermi liquid physics of gapless spin liquids arising in a family of two-and three-dimensional Kagome models. We first discuss a symmetry-protection mechanism that is responsible for the stability of the gapless phase. We then re-cast the two-dimensional Kagome spin model as a chiral Kondo lattice model that can be tackled analytically using what is in a sense a generalization of coupled-wire constructions. We provide extensive numerical evidence for a gapless spin liquid in the two-dimensional Kagome model and discuss generalizations to three dimensions. 2

Flux-driven quantum spin liquids in kagome optical lattices

“…II to argue for a spin model with three-spin terms. Although here we find that the resulting three-spin terms are staggered and relate to recent work on gapless spin liquids with nodal spinon surfaces [9]. We end with a summary and conclusion in Sec.…”

“…1b). We speculate that this flux pattern may be able to drive an interesting gapless spin liquid recently discovered numerically [9] to host symmetry protected nodal lines and may thus offer a platform to study gapless spinon surfaces [58][59][60][61]. Overall, we show that flux applied to kagome optical lattices offers a powerful tool to study QSLs, in particular, the long sought chiral spin liquid, and, possibly, a spin liquid with gapless spinon surfaces.…”

“…We conclude that large system sizes are needed to see the degeneracy because the gapless spectrum allows strong finite size effects. Numerical work on kagome ladders with as many as 200 spins show a gap [9] that decreases linearly with system size from ∼ 0.012J C for 50 spins to below 0.002J C for 200 spins, thus establishing a gapless phase for large system sizes. This work also shows that the gapless phase is stable for J C /J H 0.8.…”

“…The staggered flux ground state of Eq. 7 is argued [9] to be a gapless spin liquid where the zero-energy excitations fall along three nodal lines that all cross zero in momentum space. The gapless nodal lines are protected by symmetry but finite size effects may open a gap.…”

Noncoplanar magnetic orders and gapless chiral spin liquid on the kagome lattice with staggered scalar spin chirality

“…In spin-1 models, the same interactions give rise to a non-Abelian CSL analogous to the Moore-Read state [22][23][24]. On the other hand, three-spin interactions that induce staggered spin chiralities on the kagome lattice favor gapless spin liquids with spinon Fermi surfaces [25][26][27]. CSLs can also arise from spontaneous breaking of time reversal symmetry.…”