标题： 超越线性自旋波理论的磁极子：由磁振子包裹的介子 显示英文标题

标题： Magnetic polarons beyond linear spin-wave theory: Mesons dressed by magnons

摘要： 当一个空穴被掺入反铁磁体中时，它的运动将扭曲周围的磁序并产生磁极化子。 这种自旋和电荷自由度之间的复杂相互作用产生了非常丰富的物理现象，并被广泛认为是铜氧化物高温超导性的核心。 在本文中，我们开发了一种基于现象学部分子描述的定量理论形式，以描述强耦合 regime 中的磁极化子。 我们构建了一个与背景自旋波激发弱耦合的有效哈密顿量，使得可以使用标准的极化子方法。 我们的起点是一个掺杂到由“几何字符串”描述的 AFM 中的单个空穴，该字符串捕捉了电荷和自旋自由度的强关联跳跃过程，超越了线性自旋波近似。 随后，我们通过广义的 1/S 展开引入磁振子激发，并推导出这些自旋波与空穴加字符串（介子）的有效耦合，从而得到具有密度-密度类型相互作用的有效极化子哈密顿量。 在进行 Born-Oppenheimer 类似近似后，使用自洽 Born 近似求解该系统，以提取重整化的极化子特性。 我们将我们的形式应用于 (i) 计算超越线性自旋波的 ARPES 谱，(ii) 揭示旋转-振动介子激发的相互作用，以及 (iii) 分析低掺杂下的赝隙。 此外，我们的工作为探索非平衡或在受挫系统中的磁极化子铺平了道路，在这些系统中，弱耦合方法是可取的，而超越线性自旋波理论变得必要。 显示英文摘要

摘要： When a mobile hole is doped into an antiferromagnet, its movement will distort the surrounding magnetic order and yield a magnetic polaron. The resulting complex interplay of spin and charge degrees of freedom gives rise to very rich physics and is widely believed to be at the heart of high-temperature superconductivity in cuprates. In this paper, we develop a quantitative theoretical formalism, based on the phenomenological parton description, to describe magnetic polarons in the strong coupling regime. We construct an effective Hamiltonian with weak coupling to the spin-wave excitations in the background, making the use of standard polaronic methods possible. Our starting point is a single hole doped into an AFM described by a 'geometric string' capturing the strongly correlated hopping processes of charge and spin degrees of freedom, beyond linear spin-wave approximation. Subsequently, we introduce magnon excitations through a generalized 1/S expansion and derive an effective coupling of these spin-waves to the hole plus the string (the meson) to arrive at an effective polaron Hamiltonian with density-density type interactions. After making a Born-Oppenheimer-type approximation, this system is solved using the self-consistent Born approximation to extract the renormalized polaron properties. We apply our formalism (i) to calculate beyond linear spin-wave ARPES spectra, (ii) to reveal the interplay of ro-vibrational meson excitations, and (ii) to analyze the pseudogap expected at low doping. Moreover, our work paves the way for exploring magnetic polarons out-of equilibrium or in frustrated systems, where weak-coupling approaches are desirable and going beyond linear spin-wave theory becomes necessary.