非厄米压缩极化子
Non-Hermitian Squeezed Polarons
摘要：
最近在非厄米特超冷原子晶格实验上的突破，为实现奇异的、迄今尚未报道的多体非厄米特量子现象带来了诱人的前景。在这项工作中，我们发现并提出了一个实验平台，一个完全不同的非厄米特现象称为极化子压缩。它的特点是在非厄米互易破缺跳跃的背景下，由相互作用的杂质产生的费米子的偶极式积累。我们计算了它们的空间密度，并发现，不同于厄米极化子周围的杂质对称本地化，非厄米压缩极化子本地化不对称的方向相反，传统的非厄米泵浦和非微扰修改整个频谱，尽管有一个明显的本地配置文件。我们研究了它们的时间演化，发现它们几乎普遍存在于长时间的稳态，而不像厄米极化子只存在于基态。在我们的数值计算中，我们还发现，与众所周知的拓扑或皮肤局域态不同，压缩极化子存在于体中，与边界条件无关。我们的研究结果可能会激发在超冷原子设置中实现多体状态，其中压缩极化子可以很容易地通过成像空间费米密度来检测和表征。
英文摘要：
Recent experimental breakthroughs in non-Hermitian ultracold atomic lattices have dangled tantalizing prospects in realizing exotic, hitherto unreported, many-body non-Hermitian quantum phenomena. In this work, we discover and propose an experimental platform for a radically different non-Hermitian phenomenon dubbed polaron squeezing. It is marked by a dipole-like accumulation of fermions arising from an interacting impurity in a background of non-Hermitian reciprocity-breaking hoppings. We computed their spatial density and found that, unlike Hermitian polarons which are symmetrically localized around impurities, non-Hermitian squeezed polarons localize asymmetrically in the direction opposite to conventional non-Hermitian pumping and non-perturbatively modify the entire spectrum, despite having a manifestly local profile. We investigated their time evolution and found that, saliently, they appear almost universally in the long-time steady state, unlike Hermitian polarons which only exist in the ground state. In our numerics, we also found that, unlike well-known topological or skin localized states, squeezed polarons exist in the bulk, independently of boundary conditions. Our findings could inspire the realization of many-body states in ultracold atomic setups, where a squeezed polaron can be readily detected and characterized by imaging the spatial fermionic density.
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