Temperature dependence of the NMR relaxation rate1/T1for quantum spin chains

Abstract

We present results of numerical simulations performed on one-dimensional spin chains in order to extract the so-called relaxation rate 1/T1 accessible through NMR experiments. Building on numerical tensor network methods using the Matrix Product States (MPS) formalism, we can follow the non-trivial crossover occurring in critical chains between the high-temperature diffusive classical regime and the low-temperature response described by the Tomonaga-Luttinger liquid (TLL) theory, for which analytical expressions are known. In order to compare analytics and numerics, we focus on a generic spin-1/2 XXZ chain which is a paradigm of gapless TLL, as well as a more realistic spin-1 anisotropic chain, modelling the DTN material, which can be either in a trivial gapped phase or in a TLL regime induced by an external magnetic field. Thus, by monitoring the finite temperature crossover, we provide quantitative limits on the range of validity of TLL theory, that will be useful when interpreting experiments on quasi one-dimensional materials. arXiv:1606.09502v3 [cond-mat.str-el]

Disorder-Induced Revival of the Bose-Einstein Condensation inNi(Cl1−xBrxDupont1, Capponi2, Laflorencie3 2017Phys. Rev. Lett.Self Cite145280View full textAdd to dashboardCite

“…More precisely, exact diagonalization caculations of the effective pairwise coupling between impurities in DTNX, discussed in Ref. [28,40], yield an average energy coupling in the transverse direction J 3d 1.5x (K), which compares well with QMC estimates, at least for large enough dopings x ≥ 8% (Fig. 3).…”

“…1], combined with the local magnetizations from NMR shifts. DTNX is therefore described by the following S = 1 model [28,40]:…”

“…1 Contrary to a clean system where the S z = 1 state would disperse, here its dynamics is described by a tight-binding model with a boundary impurity potential well [40] of…”

Finite-temperature correlations in a quantum spin chain near saturation

“…For some simple cases, the development of theses DMRG-based tools has allowed to extract equilibrium correlations at finite temperatures (T-DMRG) [32,33]. This provided a welcome guidance to experiments [34][35][36] especially in situations where temperature is too high for a brute force application of field theory.…”

Nuclear magnetic resonance study of the magnetic-field-induced ordered phase in theNiCl2−4SC(NH2)2compound

“…9 However, the correctness of the TLL approach for a system which is less 1D than the above-mentioned two spin-ladder compounds has not been specifically addressed so far, and was only very recently discussed regarding NMR relaxation (dynamic) properties. 23 This question is here addressed by an NMR study of static properties of DTN, in the field close to H c2 (the transition to the fully polarized phase), in which: (1) we have accurately determined the absolute value of the order parameter (that is, the transverse, AF spin component S ⊥ ) in the BEC phase; (2) our low temperature (down to 40 mK) NMR data for the T -H phase boundary are compatible with the theoretically expected behavior for the zero-T limit,…”