Honeycomb‐Layered Oxides With Silver Atom Bilayers and Emergence of Non‐Abelian SU(2) Interactions

Abstract

Honeycomb-layered oxides with monovalent or divalent, monolayeredcationic lattices generally exhibit myriad crystalline features encompassingrich electrochemistry, geometries, and disorders, which particularly placesthem as attractive material candidates for next-generation energy storageapplications. Herein, global honeycomb-layered oxide compositions, Ag₂M₂TeO₆(M=Ni, Mg, etc.) exhibiting Ag atom bilayers with sub-valentstates within Ag-rich crystalline domains of Ag₆M₂TeO₆and Ag-deficient domains of Ag₂ˍxNi₂TeO₆(0<x<2). The Ag-rich material characterized byaberration-corrected transmission electron microscopy reveals local atomicstructural disorders characterized by aperiodic stacking and incoherency inthe bilayer arrangement of Ag atoms. Meanwhile, the global material not onlydisplays high ionic conductivity but also manifests oxygen-holeelectrochemistry during silver-ion extraction. Within the Ag-rich domains, thebilayered structure, argentophilic interactions therein and the expected Agsub-valent states (1∕2+, 2∕3+, etc.) are theoretically understood viaspontaneous symmetry breaking of SU(2)×U(1) gauge symmetry interactionsamongst 3 degenerate mass-less chiral fermion states, justified by electronoccupancy of silver 4dz₂and 5sorbitals on a bifurcated honeycomb lattice.This implies that bilayered frameworks have research applications that gobeyond the confines of energy storage.