A theory of quasiballistic spin transport

• URL: http://arxiv.org/abs/2503.15756v1
• Date: Thu, 20 Mar 2025 00:18:33 GMT
• Title: A theory of quasiballistic spin transport
• Authors: Jeffrey Song, Hyunsoo Ha, Wen Wei Ho, Vir B. Bulchandani,
• Abstract summary: "Quasiballistic spin transport" is long-lived and transiently ballistic modes of the magnetization density.<n>We develop an analytical theory of such quasiballistic spin transport.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: A recent work [Mierzejewski et al., Phys. Rev. B 107, 045134 (2023)] observed "quasiballistic spin transport" - long-lived and transiently ballistic modes of the magnetization density - in numerical simulations of infinite-temperature XXZ chains with power-law exchange interactions. We develop an analytical theory of such quasiballistic spin transport. Previous work found that this effect was maximized along a specific locus in the space of model parameters, which interpolated smoothly between the integrable Haldane-Shastry and XX models and whose shape was estimated from numerics. We obtain an analytical estimate for the lifetime of the spin current and show that it has a unique maximum along a different locus, which interpolates more gradually between the two integrable points. We further rule out the existence of a conserved two-body operator that protects ballistic spin transport away from these integrable points by proving that a corresponding functional equation has no solutions. We discuss connections between our approach and an integrability-transport conjecture for spin.

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