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arXiv 1608.03296cond-mat.dis-nncond-mat.stat-mechcond-mat.str-elquant-ph
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无序多体系统中局域守恒算符的显式构造

Explicit construction of local conserved operators in disordered many-body systems

T. E. O'Brien, Dmitry A. Abanin, Guifre Vidal, Z. Papić

摘要:

运动的局部积分--与哈密顿算子交换的准局部算子--的存在和特征编码了关于量子系统动力学的有价值的信息。特别是,强烈无序的多体系统一般可以避免热化时,有大量这样的运营商。在这项工作中,我们显式地构造局部守恒算子的$1$ D自旋链直接极小化他们的交换子的哈密顿量。我们证明了存在一个广泛的大集合的局部积分的运动在多体局域化阶段的无序XXZ自旋链。这些运营商被证明有指数衰减的尾巴,在遍历阶段的衰减是(最好的)多项式的子系统的大小。我们研究的代数性质的本地化运营商,并确认,在多体本地化阶段,他们很好地描述了“打扮”自旋运营商。

英文摘要:

The presence and character of local integrals of motion -- quasi-local operators that commute with the Hamiltonian -- encode valuable information about the dynamics of a quantum system. In particular, strongly disordered many-body systems can generically avoid thermalisation when there are extensively many such operators. In this work, we explicitly construct local conserved operators in $1$D spin chains by directly minimising their commutator with the Hamiltonian. We demonstrate the existence of an extensively large set of local integrals of motion in the many-body localised phase of the disordered XXZ spin chain. These operators are shown to have exponentially decaying tails, in contrast to the ergodic phase where the decay is (at best) polynomial in the size of the subsystem. We study the algebraic properties of localised operators, and confirm that in the many-body localised phase they are well-described by "dressed" spin operators.

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