Experimental manifestation of true magnetic ground state in a quasi-1-D spin-chain trimer iridate Ba5CuIr3O12

Quantum spin liquid (QSL) is an exotic state of matter in which the correlated magnetic moments continue to be fluctuating down to absolute zero temperature. Experimental and theoretical investigations for QSL phase have attracted considerable attention in recent condensed matter community. Geometrically frustrated magnetic lattices have been serving as the key ingredient for attaining the QSL ground state. In such a background, Ba5Ir3CuO12, a 2H-prototype spin-chain d5 iridate, is potential for accommodating exotic magnetic ground state due to the subtle balance between geometric frustration, low dimensionality, spin-orbit coupling, and structural disorder. Combined dc, ac magnetic susceptibility, and specific heat measurements clearly refute static magnetic ordering down to 0.05 K at least (neither a magnetic long-range ordering nor a spin-glass frozen state). Our zero-field (ZF) and longitudinal-field (LF) μSR characterizations down to 1.8 K refer to persistent dynamics of the iridium moments. At this point, in order to confirm the true magnetic ground state and ascertain the nature of local spin-spin correlations, we propose to perform in-depth microscopic magnetic probe μSR (both ZF and LF) measurements down to 0.04 K on EMU spectrometer of ISIS muon facility.