Spin diffusion in the low-dimensional molecular quantum Heisenberg antiferromagnetCu(pyz)(NO3)2detected with implanted muons

Abstract

We present the results of muon-spin relaxation measurements of spin excitations in the onedimensional quantum Heisenberg antiferromagnet Cu(pyz)(NO3)2. Using density-functional theory we propose muon sites and assess the degree of perturbation the muon probe causes on the system. We identify a site involving the muon forming a hydroxyl-type bond with an oxygen on the nitrate group that is sensitive to the characteristic spin dynamics of the system. Our measurements of the spin dynamics show that in the temperature range TN < T < J (between the ordering temperature TN and the exchange energy scale J) the field-dependent muon spin relaxation is characteristic of diffusive transport of spin excitations over a wide range of applied fields. We also identify a possible crossover at higher applied fields in the muon probe's response to the fluctuation spectrum, to a regime where the muon detects early-time transport with a ballistic character. This behavior is contrasted with that found for T > J and that in the related two-dimensional system Cu(pyz)2(ClO4)2.

Possible Tomonaga-Luttinger spin liquid state in the spin-1/2 inequilateral diamond-chain compound K3Cu3AlO2(SO4)4

“…The λ B for ballistic spin transport in the 1D spin-1/2 Heisenberg antiferromagnet follows a logarithmic relation λ B  ∝ ln( J / B ). In contrast, for diffusive transport, the λ B obeys the B −0.5 power-law 16,17 . As shown in the inset of Fig.…”

Finite-temperature transport in one-dimensional quantum lattice models

“…NMR studies on SrCuO 2 found diffusive relaxation (Thurber et al, 2001), while µSR experiments on high-purity samples in found ballistic relaxation (Maeter et al, 2013) (both studies probe k B T J). µSR measurements on an organic salt (Pratt et al, 2006) or on Cu(C 4 H 4 N 2 )(NO 3 ) 2 (Xiao et al, 2015) were interpreted in terms of diffusion, while a more recent µSR experiment (Huddart et al, 2020) 25 Recently, the spin-Seebeck effect was exploited to directly induce and measure spin currents in a quasi-1d cuprate material (Hirobe et al, 2017).…”

Quantum magnetism in molecular spin ladders probed with muon-spin spectroscopy

“…In addition to the materials measured in this study, also included is the half-substituted (Hpip) 2 Secondly, the longitudinal field (LF) geometry, intended to probe dynamics and applied to (Hpip) 2 CuCl 4 . Muon spin relaxation (μ + SR) has previously been shown to be a sensitive local probe of static and dynamic effects in one-and two-dimensional coordination polymer molecular magnets [13][14][15], in both TF and LF configurations. The technique has also been shown to usefully probe the phase diagram and excitations in systems based on coupled antiferromagnetic dimers [5] and in spin liquid systems [16], whose low energy physics can also be viewed as being related to that of antiferromagnetically coupled, strongly interacting dimers.…”