Crystal field excitations in the spin liquid candidate on a stuffed honeycomb lattice antiferromagnet:TbBO3

Quantum spin liquids (QSL) represent a highly entangled state of matter which lacks long-range magnetic order, despite strong exchange interactions between its magnetic constituents. QSLs are ideal hosts of exotic fractional quantum numbers coupled to emergent gauge fields and hold tantalizing prospects for applications in fault-tolerant quantum computing. The experimental realization of QSLs in 2D spin-lattice remains elusive in view of the presence of defects and anti-site disorder in real materials. Rare-earth based frustrated magnets offer a new route to realize the elusive QSL state with fractional magnetic excitations. Our focus is on a “stuffed honeycomb lattice” TbBO3 comprised of a honeycomb lattice with a superimposed triangular lattice formed by additional magnetic ions at the centre of each hexagon, that can support exotic quantum phenomena, including Dirac QSL. Our muon experiments down to 16 mK rule out the presence of magnetic ordering and spin freezing. Specific heat down to 100 mK shows no signature of magnetic ordering and specific heat shows power law behavior indicative of gapless spin excitations. NMR results suggest the presence of unconventional spin excitations in TbBO3. We propose to carry out inelastic neutron scattering (INS) studies to investigate the crystal field excitations to probe their energy and wave functions, which will shed light on the QSL state.