Valence bond phases of herbertsmithite and related copper kagome materials

Abstract

Recent evidence from magnetic torque, electron spin resonance, and second harmonic generation indicate that the prototypical quantum spin liquid candidate, herbertsmithite, has a symmetry lower than its x-ray refined trigonal space group. Here, we consider known and possible distortions of this mineral class, along with related copper kagome oxides and fluorides, relate these to possible valence bond patterns, and comment on their relevance to the physics of these interesting materials.

Dynamic fingerprint of fractionalized excitations in single-crystalline Cu3Zn(OH)6FBr

“…However, the vanishing of the matrix element is somewhat accidental and depends on the assumption of a DSL in an ideal kagome Heisenberg model. Any deviation from the ideal DSL state, e.g., a small gap in the ground state 30 , 32 , DM interactions, or other effects of perturbations 26 , 67 , changes the wave functions and may result in a constant matrix element. In that case, the Raman spectrum will be simply proportional to the DOS of the 1P component which is linear in ω .…”

“…Up to date, most, if not all, experimental information on the nature of kagome QSL relies on a single compound of Herbertsmithite. Considering the fact that a lattice distortion has recently been confirmed in Herbersmithite 24 , 25 , which stimulates investigations on the subtle magneto-elastic effect in the kagome materials 26 , 27 , an alternative realization of the QSL compound with the ideal kagome lattice is still in urgent need. Zn-Barlowite [Cu 3 Zn(OH) 6 FBr] is another candidate for a kagome QSL ground state 28 – 38 with no lattice distortion being reported yet.…”

Origin of Magnetic Ordering in a Structurally Perfect Quantum Kagome Antiferromagnet

“…Yet, even small perturbations to this simple model can stabilize fundamentally different ground states, as their influence is strongly amplified by frustration. Various factors, including further-neighbor exchange interactions [5][6][7][8][9][10][11], magnetic anisotropy [9][10][11][12][13][14], defects [14][15][16], and structural distortions [17] have been the focus of theoretical investigations in recent years. One of the seminal predictions that still calls for a clear experimental validation is a quantum critical point induced by Dzyaloshinskii-Moriya (DM) magnetic anisotropy, separating a spin liquid from a magnetically ordered ground state of KAFM [12].…”

Magnetic ordering of the distorted kagome antiferromagnet Y$_3$Cu$_9$(OH)$_{18}$[Cl$_8$(OH)] prepared via optimal synthesis

“…It would be highly relevant for future studies to determine to what extend the isotropic KAFM model is perturbed in this compound and to exactly determine its magnetically ordered ground state. Acquiring a better understanding of the effects of lattice distortions in KAFM materials is of highest importance [41], because these may even appear spontaneously to relieve frustration in the ground state, as recently suggested for the archetypal KAFM compound herbertsmithite [9].…”