De Nardis Jacopo, Gopalakrishnan Sarang, Ilievski Enej, Vasseur Romain
Department of Physics and Astronomy, University of Ghent, Krijgslaan 281, 9000 Gent, Belgium.
Department of Physics and Astronomy, CUNY College of Staten Island, Staten Island, New York 10314; Physics Program and Initiative for the Theoretical Sciences, The Graduate Center, CUNY, New York, New York 10016, USA.
Phys Rev Lett. 2020 Aug 14;125(7):070601. doi: 10.1103/PhysRevLett.125.070601.
Finite-temperature spin transport in the quantum Heisenberg spin chain is known to be superdiffusive, and has been conjectured to lie in the Kardar-Parisi-Zhang (KPZ) universality class. Using a kinetic theory of transport, we compute the KPZ coupling strength for the Heisenberg chain as a function of temperature, directly from microscopics; the results agree well with density-matrix renormalization group simulations. We establish a rigorous quantum-classical correspondence between the "giant quasiparticles" that govern superdiffusion and solitons in the classical continuous Landau-Lifshitz ferromagnet. We conclude that KPZ universality has the same origin in classical and quantum integrable isotropic magnets: a finite-temperature gas of low-energy classical solitons.
已知量子海森堡自旋链中的有限温度自旋输运是超扩散的，并且据推测属于 Kardar-Parisi-Zhang（KPZ）普适类。利用一种输运动力学理论，我们直接从微观层面计算了海森堡链的 KPZ 耦合强度随温度的变化；结果与密度矩阵重整化群模拟结果吻合得很好。我们在控制超扩散的“巨型准粒子”与经典连续朗道 - 里夫希茨铁磁体中的孤子之间建立了严格的量子 - 经典对应关系。我们得出结论，KPZ 普适性在经典和量子可积各向同性磁体中有相同的起源：低能经典孤子的有限温度气体。
