一维量子系统中的扩散和弹道输运
Diffusion and ballistic transport in one-dimensional quantum systems
摘要：
可积一维（1D）系统中的输运必然是弹道输运。因此，在S=1/2的一维海森堡模型的近乎理想的实现中，实验上看到的大扩散响应是令人困惑的，到目前为止还没有得到解释。在这里，我们表明，与通常的信念相反，扩散普遍存在于相互作用的一维系统受到周期性的晶格势。我们提出了一个无参数的自旋-晶格弛豫速率公式，它与实验非常吻合。此外，我们计算的电流衰减直接在热力学极限使用时间相关的密度矩阵重整化群算法，并表明，即使在高温下存在一个巨大的时间尺度。
英文摘要：
It has been conjectured that transport in integrable one-dimensional (1D) systems is necessarily ballistic. The large diffusive response seen experimentally in nearly ideal realizations of the S=1/2 1D Heisenberg model is therefore puzzling and has not been explained so far. Here, we show that, contrary to common belief, diffusion is universally present in interacting 1D systems subject to a periodic lattice potential. We present a parameter-free formula for the spin-lattice relaxation rate which is in excellent agreement with experiment. Furthermore, we calculate the current decay directly in the thermodynamic limit using a time-dependent density matrix renormalization group algorithm and show that an anomalously large time scale exists even at high temperatures.
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