Spin dynamics of the antiferromagnetic spin-12chain at finite magnetic fields and intermediate temperatures

Abstract

We present a study of the dynamic structure factor of the antiferromagnetic spin-1 2 Heisenberg chain at finite temperatures and finite magnetic fields. Using quantum Monte Carlo based on the stochastic series expansion and maximum entropy methods, we evaluate the longitudinal and the transverse dynamic structure factors from vanishing magnetic fields up to and above the threshold B c for ferromagnetic saturation, as well as for high and for intermediate temperatures. We study the field-induced redistribution of spectral weight contrasting longitudinal versus transverse excitations. At finite fields below saturation incommensurate low-energy modes are found consistent with zero-temperature Bethe ansatz. The crossover between the field-induced ferromagnet above B c and the Luttinger liquid below B c is analyzed in terms of the transverse spin dynamics. Evaluating sum rules we assess the quality of the analytic continuation and demonstrate excellent consistency of the maximum entropy results.

Low temperature ballistic spin transport in theS= 1/2 antiferromagnetic Heisenberg chain compound SrCuO2

“…In our situation we have T ≈75 K, and J≈2000 K, i.e. T ≪J, and we cannot apply the results of Grossjohann et al [9] for the explanation of our experiments. Also, similar diffusive behavior was predicted within the field-theoretical approximation [10].…”

Symmetry-conserving purification of quantum states within the density matrix renormalization group

“…[3][4][5] On the experimental front, recent advances [6][7][8][9] have enabled very precise measurements of both static and dynamical correlation functions. These experimental results are challenging the available theoretical and computational techniques, [10][11][12] increasing demand to develop efficient and accurate numerical methods for the investigation and eventual prediction of the thermodynamic quantities.…”

Fractionalization, entanglement, and separation: Understanding the collective excitations in a spin-orbital chain

“…A reference system: spin chain Fractional excitation. In a spin S = 1/2 chain, when the spins show ferromagnetic (FM) alignments, the elementary excitations are S = 1 spin-flip (magnon) excitations, and the corresponding spectrum exhibits a sharp, single-magnon mode [1][2][3] . Naively, one might expect a similar scenario for the S = 1/2 Heisenberg chain with nearest-neighbor (NN) antiferromagnetic (AF) interactions.…”

“…Spinons in an AF background are deconfined, as they can move away from each other spatially without costing extra energy. The spectrum of a spin-flip excitation (creating two spinons) thereby develops an energy continuum [1][2][3]8 . This is quite different when spin degeneracy is lifted by a magnetic field H z .…”