Low-Temperature Spin Diffusion in a Highly IdealS=12Heisenberg Antiferromagnetic Chain Studied by Muon Spin Relaxation

Abstract

The organic radical-ion salt DEOCC-TCNQF4 contains linear chains of stacked molecules with significant Heisenberg antiferromagnet interactions along the chain and extremely weak interactions between the chains. Zero-field muSR has confirmed the absence of long-range magnetic order down to 20 mK and field-dependent muSR is found to be consistent with diffusive motion of the spin excitations. The anisotropic spin dynamics and the upper boundary for magnetic ordering temperature both indicate interchain magnetic coupling /J'/<7 mK. As the intrachain coupling J is 110 K, /J'/J/ is significantly less than 10(-4). This system therefore provides one of the most ideal examples of the one-dimensional S=1/2 Heisenberg antiferromagnet yet discovered.

Conservation laws, integrability, and transport in one-dimensional quantum systems

“…57 It is important to note that in the NMR experiment of Ref. [54], the q-dependence of the form factor suppresses the contribution from q ∼ π modes in the autocorrelation function, so that the 1/T 1 signal is completely dominated by q ∼ 0 modes.…”

Vanishing spin stiffness in the spin-12Heisenberg chain for any nonzero temperature

“…Indeed, only some of the solutions to the general Bethe-ansatz equation, Eq. (24), are in terms of real rapidities Λ j . There also exist solutions involving groups of complex rapidities [33,34].…”

“…One-dimensional (1D) correlated lattice systems with L sites show exotic spin transport properties at finite temperature T > 0 whose nature has been a problem of long-standing both theoretical [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and experimental [21][22][23][24][25][26][27] interest. Often integrable quantum systems show dissipationless ballistic transport behavior.…”

Another dimension: investigations of molecular magnetism using muon–spin relaxation

“…An even more ideal example of this physics is found in the radical system DEOCC-TCNQF 4 [27]. In this case no LRO transition is observed using µ + SR down to 20 mK, constraining |J ⊥ /J| < 6 × 10 −5 , making this the most successful realization of a 1DQHAFM yet reported.…”