Real-time dynamics induced by quenches across the quantum critical points in gapless Fermi systems with a magnetic impurity
Real-time dynamics induced by quenches across the quantum critical points in gapless Fermi systems with a magnetic impurity
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DOI：
10.1103/physrevb.90.235145
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发表时间：
2014-12-24
影响因子：
3.7
通讯作者：
Anders, Frithjof B.
中科院分区：
文献类型：
--
作者：
Kleine, Christian;Musshoff, Julian;Anders, Frithjof B.
在赝能隙单杂质安德森模型中，费米子从定域轨道以与能量相关的速率γ（γ）正比于垂直条数r的能量相关散射产生了量子临界点（QCP），它将具有非屏蔽自旋矩的局域矩相与稍微偏离标准近藤问题屏蔽相的强耦合相分离.使用随时间变化的数值重整化群（TD-NRG）的方法，我们表明，即使淬火跨QCP，但与系统的偏差从热平衡取决于距离的临界耦合的局部动力学性质总是朝着一个稳态值平衡。局部非平衡性质的相互作用猝灭和杂交猝灭。我们增加了我们的数值数据的分析计算，在短时间内变得准确，并找到良好的协议之间的数值和分析理论。对于相互作用淬灭的筛选阶段内，我们发现了一个通用的功能的时间依赖性的本地双重占用。我们追溯我们的结果和Gutzwiller理论中的波函数的约束的依赖于时间的Gutzwiller变分方法获得的数据之间的差异：而NRG基态适当地占形成一个扩展的自旋力矩，从系统中的未屏蔽阶段，Gutzwiller理论只允许形成的自旋力矩的局部杂质轨道。
The energy-dependent scattering of fermions from a localized orbital at an energy-dependent rate Gamma(epsilon) proportional to vertical bar epsilon vertical bar(r) gives rise to quantum critical points (QCPs) in the pseudogap single-impurity Anderson model separating a local moment phase with an unscreened spin moment from a strong-coupling phase which slightly deviates from the screened phase of standard Kondo problem. Using the time-dependent numerical renormalization group (TD-NRG) approach we show that local dynamic properties always equilibrate towards a steady-state value even for quenches across the QCP but with systematic deviations from the thermal equilibrium depending on the distance to the critical coupling. Local nonequilibrium properties are presented for interaction quenches and hybridization quenches. We augment our numerical data by an analytical calculation that becomes exact at short times and find excellent agreement between the numerics and the analytical theory. For interaction quenches within the screened phase we find a universal function for the time-dependent local double occupancy. We trace back the discrepancy between our results and the data obtained by a time-dependent Gutzwiller variational approach to restrictions of the wave-function ansatz in the Gutzwiller theory: while the NRG ground states properly account for the formation of an extended spin moment which decouples from the system in the unscreened phase, the Gutzwiller ansatz only allows the formation of the spin moment on the local impurity orbital.