Fincher-Burke spin excitations and ωT scaling in insulating La1.95 Sr0.05 CuO4

Insulating La1.95 Sr0.05 CuO4 shares with superconducting cuprates the same Fincher-Burke spin excitations, which usually are observed in itinerant antiferromagnets. The local spectral function satisfies ωT scaling above ∼16 K for this incommensurate insulating cuprate, together with previous results in commensurate insulating and incommensurate superconducting cuprates, further supporting the general prediction for square-lattice quantum spin S=12 systems. The width of incommensurate peaks in La1.95 Sr0.05 CuO4 scales to a similar finite value as at optimal doping, strongly suggesting that they are similarly distant from a quantum critical point. They might both be limited to a finite correlation length by partial spin-glass freezing.