Coherent quantum transport in disordered systems I: The influence of dephasing on the transport properties and absorption spectra on one-dimensional systems
Excitonic transport in static disordered one dimensional systems is studied in the presence of thermal fluctuations that are described by the Haken-Strobl-Reineker model. For short times, non-diffusive behavior is observed that can be characterized as the free-particle dynamics in the Anderson localized system. Over longer time scales, the environment-induced dephasing is sufficient to overcome the Anderson localization caused by the disorder and allow for transport to occur which is always seen to be diffusive. In the limiting regimes of weak and strong dephasing quantum master equations are developed, and their respective scaling relations imply the existence of a maximum in the diffusion constant as a function of the dephasing rate that is confirmed numerically. In the weak dephasing regime, it is demonstrated that the diffusion constant is proportional to the square of the localization length which leads to a significant enhancement of the transport rate over the classical prediction. Finally, the influence of noise and disorder on the absorption spectrum is presented and its relationship to the transport properties is discussed.
Electron transport in a disordered graphene nanoribbon with zigzag edges is crucially affected by a perfectly conducting channel (PCC), which is stabilized if intervalley scattering is ignorable. In the presence of such a PCC, the dimensionless conductance g of the system decreases to the quantized value of g = 1 with increasing system length L. In the realistic case where intervalley scattering is weak but not ignorable, the PCC is gradually destabilized with increasing L, and g eventually decays to zero owing to the onset of Anderson localization. Here, we show that such destabilization of t…
Disordered electron liquid in double quantum well heterostructures: Renormalization group analysis and dephasing rate
我们报告了电子-电子相互作用对物理观测量(电导等)的影响的详细研究。双量子阱异质结构中的无序电子液体。我们发现,即使在两个量子阱中的电子的共同弹性散射的情况下,在量子阱中的电子-电子相互作用的不对称性和内部在低温下使他们困惑。我们的研究结果与最近的量子阱Al $_x$ Ga $_{1-x}$ As/GaAs/Al $_x$ Ga $_{1-x}$ As异质结的输运实验定量一致。
We study the interplay between dephasing, disorder, and openness on transport efficiency in a one-dimensional chain of finite length $N$, and in particular the beneficial or detrimental effect of dephasing on transport. The excitation moves along the chain by coherent nearest-neighbor hopping $Ω$, under the action of static disorder $W$ and dephasing $γ$. The system is open due to the coupling of the last site with an external acceptor system (sink), where the excitation can be trapped with a rate $Γ_{\rm trap}$, which determines the opening strength. While it is known that dephasing can help …
As a potential window on transitions out of the ergodic, many-body-delocalized phase, we study the dephasing of weakly disordered, quasi-one-dimensional fermion systems due to a diffusive, non-Markovian noise bath. Such a bath is self-generated by the fermions, via inelastic scattering mediated by short-ranged interactions. We calculate the dephasing of weak localization perturbatively through second order in the bath coupling. However, the expansion breaks down at long times, and is not stabilized by including a mean-field decay rate, signaling a failure of the self-consistent Born approximat…
In ferromagnetic metals, transverse spin currents are thought to be absorbed via dephasing -- i.e., destructive interference of spins precessing about the strong exchange field. Yet, due to the ultrashort coherence length of $\approx$1 nm in typical ferromagnetic thin films, it is difficult to distinguish dephasing in the bulk from spin-flip scattering at the interface. Here, to assess which mechanism dominates, we examine transverse spin-current absorption in ferromagnetic NiCu alloy films with reduced exchange fields. We observe that the coherence length increases with decreasing Curie tempe…
Comment on "Quantum Decoherence in Disordered Mesoscopic Systems"
在最近的一篇论文中,Phys. Rev. Lett. 81,1074(1998),Golubev和Zaikin(GZ)发现“电子的零点波动”有助于从磁阻中提取的退相速率。结果,失相速率在零温度下保持有限。GZ声称他们的结果“与实验数据吻合良好”。我们指出,GZ的结果与(i)相互作用对弱局域化(WL)的影响的传统微扰理论,(ii)与现有的实验数据是不相容的。GZ发现的更详细批评见cond-mat/9808053。
Dephasing and Hyperfine Interaction in Carbon Nanotubes Double Quantum Dots: Disordered Case
本文从理论上研究了半导体碳纳米管(CNTs)中双量子点(DQD)中的\emph{return probability experiment},用于测量退相时间$T_2^*$.退相是由于与${}^{13}$ C核自旋的超精细相互作用。由于谷自由度和自旋自由度,对于量子点中的任何给定纵模,存在四个束缚态。在零磁场下,自旋-轨道耦合和谷混合将这四个态分裂成两个Kramers双峰。对于一个给定的点的谷混合项是由点内无序,因此在属于不同的点的Kramers双重态是不同的。我们展示了如何非零的单粒子interdot隧穿振幅属于不同的双峰状态之间产生新的避免交叉,作为失谐的函数,在相关的两个粒子的光谱,交叉从两个电子在一个点的状态配置,$(0,2)$,在每个点的配置,$(1,1)$的一个电子。与清洁系统相比,多个朗道-齐纳过程影响每个单次测量的分离和连接阶段,并且它们以强烈依赖于初始状态的方式影响测量结果。我们发现,一个定义明确的返回概率实验实现时,在每个单激发周期,(0,2)基态的准备。在这种情况下,谷混合增加了测量的返回概率的饱和值,而返回到(0,2)基态的概率保持不变。最后,我们研究了高磁场极限下的谷混合效应;对于平行的磁场,预测结果与干净的纳米管一致,而无序效应总是与垂直于纳米管轴的磁场相关。
We explore various aspects of magneto-conductance oscillations in semiconductor nanowires, developing quantum transport models based on the non-equilibrium Green's function formalism. In the clean case, Aharonov-Bohm (AB - h/e) oscillations are found to be dominant, contingent upon the surface confinement of electrons in the nanowire. We also numerically study disordered nanowires of finite length, bridging a gap in the existing literature. By varying the nanowire length and disorder strength, we identify the transition where Al'tshuler-Aronov-Spivak (AAS - h/2e) oscillations start dominating,…
Structural correlations have a significant effect on light propagation in disordered media. We numerically investigate the role of short-range order in light absorption in thin films with disordered nanoholes. Two types of disordered distributions, including stealthy hyperuniform (SHU) and hard disk (HD) patterns with different degrees of short-range order, are studied. We find that Bragg scattering induced by short-range order results in the appearance of a gradually sharper absorption peak with the increasing of degrees of short-range order ($χ$, $ϕ$). A physical model is proposed to calcula…
The interpretation of nanoplasmonic effects on molecular properties, such as metal-enhanced absorption or fluorescence, typically assumes a fully coherent picture (in the quantum-mechanical sense) of the phenomena. Yet, there may be conditions where the coherent picture breaks down, and decoherence effect should be accounted for. Using a state-of-the-art multiscale model approach able to include environment-induced dephasing, here we show that metal nanoparticle effects on the light absorption by a nearby molecule is strongly affected (even qualitatively, i.e., suppression vs enhancement) by m…
We explore the combined impact of sulfur vacancies and electronic interactions on the optical properties of monolayer MoS$_2$. First, we present a generalized Anderson-Hubbard Hamiltonian that accounts for both randomly distributed sulfur vacancies and the presence of dielectric screening within the material. Second, we parameterize this energy-dependent Hamiltonian from first-principles calculations based on density functional theory and the Green function and screened Coulomb (GW) method. Third, we apply a first-principles-based many-body typical medium method to determine the single-particl…