A theory of quasiballistic spin transport
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866917140054933504 |
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| author | Song, Jeffrey Z. Ha, Hyunsoo Ho, Wen Wei Bulchandani, Vir B. |
| author_facet | Song, Jeffrey Z. Ha, Hyunsoo Ho, Wen Wei Bulchandani, Vir B. |
| contents | 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_15756 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A theory of quasiballistic spin transport Song, Jeffrey Z. Ha, Hyunsoo Ho, Wen Wei Bulchandani, Vir B. Statistical Mechanics Quantum Gases Strongly Correlated Electrons Quantum Physics 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. |
| title | A theory of quasiballistic spin transport |
| topic | Statistical Mechanics Quantum Gases Strongly Correlated Electrons Quantum Physics |
| url | https://arxiv.org/abs/2503.15756 |