Time-dependent correlations of the one-dimensional isotropic XY model

Finite-temperature correlations in a quantum spin chain near saturation

“…Close to this point quantum critical scaling is expected [3] and the system goes to a free fermion fixed point [39]. This allows us to use a Fredholm determinant technique to compute the scaling function exactly [40][41][42]. In addition to this universal scaling part, the nonuniversal part includes a robust thermally activated longitudinal mode, which remains visible and underdamped across the entire Brillouin zone and in an energy range far exceeding the temperature scale.…”

Analytical Polarization and Coherence Transfer Functions for Three Dipolar Coupled Spins 12

“…3). In particular, the transfer between spins 1 and 2 is quenched if D 13 and D 23 have opposite signs and ͉D 13 ͉ Ϸ ͉D 23 ͉ Ͼ ͉D 12 ͉. This is the case for the transfer shown in Fig.…”

“…As expected, the transfer efficiency can be either positive or negative. Note that in contrast to the transfer of z magnetization, significant transfer of x magnetization occurs if D 13 and D 23 have opposite signs and ͉D 13 ͉ Ϸ ͉D 23 ͉ Ͼ ͉D 12 ͉. Hence, in some cases, the quenching of polarization transfer can be circumvented by transferring x rather than z magnetization.…”

Dynamic Correlations in a Random Spin-1/2 XY Chain

“…Let us consider the strong-field zero temperature case |Ω | > |J| and β → ∞ when the dynamic structure factorsS αβ (κ, ω) are as follows:S xx (κ, ω) = isgn(Ω )S xy (κ, ω) = (π/2)δ(ω − |Ω | − J cos κ) [4]. As a result, after some calcula-tions we find…”

“…S xx (κ, ω) for 1/2 ≤ p ≤ 1 follows from (6) after the change κ → κ ∓ π. Equation (6) contains the above-mentioned exact result [4] in the nonrandom limit ξ → ∞ (when p = 0 or p = 1). In the opposite limit of strong disorder ξ = 0 (when p = 1/2) the right hand side of (6) transforms into…”