We study the effect of suddenly turning on a long-range interaction in a spinless Fermi gas in two dimensions. The short to intermediate time dynamics is obtained using the method of bosonization of the Fermi surface. This allow to calculate the full space-time dependence of the non-equilibrium fermion density matrix as well as the evolution of the quasiparticle residue after the quench. It is thus found that the asymptotic state predicted by bosonization is consistent with the prethermalized state. From the bosonized representation, we explicitly construct the Generalized Gibbs Ensamble that describes the prethermalized state. A protocol to perform an interaction quantum quench in a dipolar gas of Erbium atoms is also described.
Prethermalization in a quenched one-dimensional quantum fluid of light: Intrinsic limits to the coherent propagation of a light beam in a nonlinear optical fiber
Crossover from adiabatic to sudden interaction quenches in the Hubbard model: Prethermalization and nonequilibrium dynamics
最近在光晶格中的凝聚态模型的实验实现激发了对其非平衡行为的研究。基于有效BCS哈密顿量,已经对配对相互作用突然猝灭后超导体的动力学进行了预测;然而,它们的实验验证需要沿着双重约束制备哈伯德模型的合适激发态:(i)充分非绝热的斜坡方案对于激发非平衡动力学是必要的,以及(ii)必须避免超过超导性的临界温度的过热。对于通常讨论的相互作用斜坡,相应的能量尺度没有明确的分离。在这里,我们表明,这两个条件的匹配被简化的超冷费米子系统的内在弛豫行为:对于一个特殊的例子,我们检查的线性斜坡的预热化的瞬态制度[M。Moeckel和S. Kehrein,Phys. Rev. Lett. 100,175702(2008)]在使用Keldysh微扰理论从突然切换到绝热切换的交叉下。的动量分布的实时分析表现出早期的能量弛豫和后来的热化散射事件的时间分离。对于长但有限的斜升时间,该间隔可能很大。在预热化制度的动量分布类似于零温度费米液体的能量插入的斜坡仍然位于高能量模式。因此,超冷费米子被证明对加热具有鲁棒性,这简化了光晶格中非平衡BCS动力学的观察。
We study the prethermalization and thermalization dynamics of local observables in weakly perturbed nonintegrable systems, with Hamiltonians of the form $\hat{H}_0+g\hat{V}$, where $\hat{H}_0$ is nonintegrable and $g\hat{V}$ is a perturbation. We explore the dynamics of far from equilibrium initial states in the thermodynamic limit using a numerical linked cluster expansion (NLCE), and in finite systems with periodic boundaries using exact diagonalization. We argue that generic observables exhibit a two-step relaxation process, with a fast prethermal dynamics followed by a slow thermalizing on…
We investigate the formation of quasisteady states in one-dimensional pumps of interacting fermions at non-integer filling fraction, in the regime where the driving frequency and interaction strength are small compared to the instantaneous single-particle band gap throughout the driving cycle. The system rapidly absorbs energy from the driving field, and approaches a quasisteady state that locally resembles a maximal entropy state subject to the constraint of fixed particle number in each of the system's single-particle Floquet bands. We explore the nature of this quasisteady state through one…
这些笔记涵盖了我在2012年Les Houches暑期学校的一些详细讲座。我在这里描述的工作做了迪帕克Iyer与重要贡献胡杰关。我讨论了量子猝灭揭示的物理学的某些方面,并提出了一种研究可积系统的猝灭动力学的形式主义。该方法推广了Yudson的方法,并应用于描述$N$相互作用玻色子气体在连续无限直线上运动并通过短程势相互作用的Lieb-Liniger模型.我们进行淬火从几个初始状态和任何数量的粒子和计算的密度和噪声的相关性的演变。在很长的时间限制系统稀释,我们发现,对于任何值的排斥耦合独立的初始状态的系统渐近线对astrongly排斥气体,而对于任何值的吸引力耦合,系统形成一个最大的束缚态,占主导地位,在较长的时间。在这两种情况下,系统平衡,但不热化,一个效果,这是符合预热化。这些结果可以用实验来验证。有关更多细节,请参见:Phys. Rev. A 87,053628(2013),这些笔记是基于此。海森堡模型和安德森模型的方法的进一步应用将在其他地方介绍。
Far-from-equilibrium field theory of many-body quantum spin systems: Prethermalization and relaxation of spin spiral states in three dimensions
本文从理论上研究了三维各向同性海森堡模型中自旋螺旋态的远离平衡弛豫动力学。所研究的问题作为一个原型理解孤立的多体系统的量子动力学在附近的一个自发破缺的连续对称性。我们提出了一个场论的形式主义,系统地改善了平均场描述的通用自旋1/2系统的实时量子动力学。这是通过将自旋映射到马约拉纳费米子,然后对所得的两粒子不可约(2 PI)有效作用量进行1/N展开来实现的。我们的分析揭示了丰富的涨落诱导的弛豫动力学的自旋螺旋态的幺正演化。特别是,我们发现突然出现的长寿命prethermalized高原与分散的寿命的螺旋绕组是朝着磁稳定的铁或反铁磁相调谐。新兴的预热化状态的特点是不同的玻色子模式被热填充在不同的有效温度,并通过一个层次的松弛过程让人想起玻璃系统。通过求解非平衡Bethe-Salpeter方程发现的自旋-自旋关联因子提供了对关联的动态形成、不稳定集体模式的命运以及涨落-耗散关系的出现的进一步了解。我们的预言可以用最近在量子气体显微镜中实现的超冷原子自旋螺旋态的实验来验证[S。Hild等人,Phys. Rev. Lett. 113,147205(2014)]。
We study heating dynamics in isolated quantum many-body systems driven periodically at high frequency and large amplitude. Combining the high-frequency expansion for the Floquet Hamiltonian with Fermi's golden rule (FGR), we develop a master equation termed the Floquet FGR. Unlike the conventional one, the Floquet FGR correctly describes heating dynamics, including the prethermalization regime, even for strong drives, under which the Floquet Hamiltonian is significantly dressed, and nontrivial Floquet engineering is present. The Floquet FGR depends on system size only weakly, enabling us to an…
We consider non-equilibrium dynamics of two initially independent reservoirs $A$ and $B$ filled with a cold Fermi gas coupled and decoupled by two quantum quenches following one another. We find that the von Neumann entropy production induced by the quench is faster than thermal transport between the reservoirs and defines the short-time dynamics of the system. We analyze the energy change in the system which adds up the heat transferred between $A$ and $B$ and the work done by the quench to uncouple the reservoirs. In the case when $A$ and $B$ interact for a short time, we notice an energy in…
Particle entanglement provides information on quantum correlations in systems of indistinguishable particles. Here, we study the one particle entanglement entropy for an integrable model of spinless, interacting fermions both at equilibrium and after an interaction quantum quench. Using both large scale exact diagonalization and time dependent density matrix renormalization group calculations, we numerically compute the one body reduced density matrix for the J-V model, as well as its post-quench dynamics. We include an analysis of the fermionic momentum distribution, showcasing its time evolu…
We present an experimental study of a two component Fermi gas following an interaction quench into the superfluid phase. Starting with a weakly attractive gas in the normal phase, interactions are ramped to unitarity at a range of rates and we measure the subsequent dynamics as the gas approaches equilibrium. Both the formation and condensation of fermion pairs are mapped via measurements of the pair momentum distribution and can take place on very different timescales, depending on the adiabaticity of the quench. The contact parameter is seen to respond very quickly to changes in the interact…
Dynamical properties of two-component mass-imbalanced few-fermion systems confined in a one-dimensional harmonic trap following a sudden quench of interactions are studied. It is assumed that initially the system is prepared in the non-interacting ground state and then, after a sudden quench of interactions, the unitary evolution is governed by interacting many-body Hamiltonian. By careful analysis of the evolution of the Loschmidt echo, density distributions of the components, and entanglement entropy between them, the role of mass imbalance and particle number imbalance on the system's evolu…
Using a Luttinger liquid theory we investigate the time evolution of the particle density of a one-dimensional fermionic system with open boundaries and subject to a finite duration quench of the inter-particle interaction. We provide analytical and asymptotic solutions to the unitary time evolution of the system, showing that both switching on and switching off the quench ramp create light-cone perturbations in the density. The post-quench dynamics is strongly affected by the interference between these two perturbations. In particular, we find that the discrepancy between the time-dependent d…
We unravel the ground state properties and the non-equilibrium quantum dynamics of two bosonic impurities immersed in an one-dimensional fermionic environment by applying a quench of the impurity-medium interaction strength. In the ground state, the impurities and the Fermi sea are phase-separated for strong impurity-medium repulsions while they experience a localization tendency around the trap center for large attractions. We demonstrate the presence of attractive induced interactions mediated by the host for impurity-medium couplings of either sign and analyze the competition between induce…