Accurate determination of the exchange constant in Sr2CuO3 from recent theoretical results

Tomonaga-Luttinger Spin Liquid and Kosterlitz-Thouless Transition in the Spin-1/2 Branched Chains: The Study of Topological Phase Transition

In the present work, we provide a comprehensive numerical investigation of the magnetic properties and phase spectra of three types of spin-1/2 branched chains consisting of one, two and three side spins per unit block with intra-chain interaction and a uniform inter-chain interaction in the presence of an external magnetic field. In a specific magnetic field interval, the low-temperature magnetization of these chains shows a step-like behavior with a pronounced plateau depending on the strength and the type of intra-chain interaction being ferromagnetic or antiferromagnetic. We demonstrate that when inter-chain interaction J1 is antiferromagnetic and intra-chain interaction J2 is ferromagnetic, the magnetization of the models manifests a smooth increase without a plateau, which is evidence of the existence of a Luttinger-like spin liquid phase before reaching its saturation value. On the other hand, when J1 is ferromagnetic and J2 is antiferromagnetic, the low-temperature magnetization of the chain with two branches shows an intermediate plateau at one-half of the saturation magnetization that breaks a quantum spin liquid phase into two regions. The magnetization of the chain with three branches exhibits two intermediate plateaus and two regions of a quantum spin liquid. We demonstrate that the chains with more than one side spin illustrate in their ground-state phase diagram a Kosterlitz–Thouless transition from a gapful phase to a gapless spin liquid phase.

[BDTA]2[Cu(mnt)2]: An Almost Perfect One-Dimensional Magnetic Material

[BDTA]2[Cu(mnt)2] (BDTA = benzo-1,3,2-dithiazolyl, mnt = maleonitriledithiolate) was crystallized in the space group P with an inversion center on Cu giving a stacked structure with each metal complex anion sandwiched by two cations. Short intermolecular S...S contacts give rise to a one-dimensional chain lateral to the stacking axis. Variable-temperature magnetic susceptibility and EPR measurements indicate that the salt behaves as an ideal one-dimensional Heisenberg antiferromagnetic material from 2 K < or = T < or = 300 K, with a coupling constant of J/k(B) = 16-17 K; the very low temperature magnetic properties are in quantitative agreement with the predictions of quantum field theory. DFT calculations are consistent with the formation of a one-dimensional magnetic chain with interstack interactions mediated by the BDTA counterions.

Boundary susceptibility in the spin-1/2 chain: Curie-like behavior without magnetic impurities

We investigate the low-temperature thermodynamics of the spin-1/2 Heisenberg chain with open ends. On the basis of boundary conformal field theory arguments and numerical density matrix renormalization group calculations, it is established that in the isotropic case the impurity susceptibility exhibits a Curie-like divergent behavior as the temperature decreases, even in the absence of magnetic impurities. A similar singular temperature dependence is also found in the boundary contributions of the specific heat coefficient. In the anisotropic case, for 1/2<Delta<1, these boundary quantities still show a singular temperature dependence obeying a power law with an anomalous dimension. Experimental consequences will be discussed.