In this letter we study the coherent electronic transport through a metallic nanowire with magnetic impurities. The spins of these impurities are considered as frozen to mimic a low temperature spin glass phase. The transport properties of the wire are derived from a numerical Landauer technique which provides the conductance of the wire as a function of the disorder configuration. We show that the correlation of conductance between two spin configurations provides a measure of the correlation between these spin configurations. This correlation corresponds to the mean field overlap in the absence of any spatial order between the spin configurations. Moreover, we find that these conductance correlations are sensitive to the spatial order between the two spin configurations, i.e whether the spin ?ips between them occur in a compact region or not.
Periodically driven systems, which can be described by Floquet theory, have been proposed to show characteristic behavior that is distinct from static Hamiltonians. Floquet theory proposes to describe such periodically driven systems in terms of states that are indexed by a photon number in addition to the usual Hilbert space of the system. We propose a way to measure directly this additional Floquet degree of freedom by the measurement of the DC conductance of a single channel quantum point contact. Specifically, we show that a single channel wire augmented with a grating structure when irrad…
本文综述了光子边带的几个应用，Buttiker和Landauer在他们的隧道穿越时间理论中使用[Phys. Rev. Lett. 49，1739（1982）]，在介观系统的传输和光学中。主题包括传输理论的推广，以时间相关的情况下，光学和太赫兹电磁场中的介观系统的运输，和相位测量光子辅助隧道通过量子点。
We study the radiative heat transfer between two semi-infinite half-spaces, bounded by conductive surfaces in contact with vacuum. This setup is interpreted as a four-terminal mesoscopic transport problem. The slabs and interfaces are viewed as bosonic reservoirs, coupled perfectly to a scattering center consisting of the two interfaces and vacuum. Using Rytov's fluctuational electrodynamics and assuming Kirchhoff's circuital law, we calculate the heat flow in each bath. This allows for explicit evaluation of a conductance matrix, from which one readily verifies Büttiker symmetry. Thus, radiat…
The Landauer-Butikker formalism is an important formalism to study mesoscopic systems. Its validity for linear transport is well established theoretically as well as experimentally. Akkermans et al [Phys. Rev. Lett. {\bf 66}, 76 (1991)] had shown that the formalism can be extended to study thermodynamic properties like persistent currents. It was earlier verified for simple one dimensional systems. We study this formula very carefully and conclude that it requires reinterpretation in quasi one dimension. This is essentially because of the presence of evanescent modes in quasi one dimension.
In this paper, we propose a method to calculate the exact Taylor series of the scattering matrix in general multiterminal tight-binding systems to arbitrary order N, which allows us to find the Taylor expansion of Landauer conductance in mesoscopic systems. The method is based on the recursive scattering matrix method (RSMM) that permits us to find the scattering matrix of a system from the scattering matrices of its subsystems. Following ideas of automatic differentiation, we determine expressions for the sum, product, inverse, and diagonalization of a matrix Taylor expansion, and use them in…
Spin relaxation in mesoscopic Ag wires in the diffusive transport regime is studied via nonlocal spin valve and Hanle effect measurements performed on permalloy/Ag lateral spin valves. The ratio between momentum and spin relaxation times is not constant at low temperatures. This can be explained with the Elliott-Yafet spin relaxation mechanism by considering the momentum surface relaxation time as being temperature dependent. We present a model to separately determine spin flip probabilities for phonon, impurity and surface scattering and find that the spin flip probability is highest for surf…
We study particle current in a recently proposed model for coherent quantum transport. In this model a system connected to mesoscopic Fermi reservoirs (meso-reservoir) is driven out of equilibrium by the action of super reservoirs thermalized to prescribed temperatures and chemical potentials by a simple dissipative mechanism described by the Lindblad equation. We compare exact (numerical) results with theoretical expectations based on the Landauer formula
The Landauer formula allows us to describe theoretically the conductance in terms of the transmission function in a mesoscopic system. We propose a general method to evaluate the transmission function in the complex domain for systems connected to semi-infinite atomic chains. This reveals the presence of complex-conjugated pairs of simple poles that are responsible for transmission peaks in the real-domain evaluations. This leads us to formulate a closed-form expression for the transmission function.
Ballistic transport through an impurity-free section of the Corbino disk in graphene is investigated by means of the Landauer-Büttiker formalism in the mesoscopic limit. In the linear-responce regime the conductance is quantized in steps close to integer multiples of $4e^{2}/h$, yet Fabry-Perot oscillations are strongly suppressed. The quantization arises for small opening angles $θ\lesssimπ/3$ and large radii ratios $R_2/R_1\gtrsim{}10$. We find that the condition for emergence of the $n$-th conductance step can be written as $\sqrt{n}θ/π\ll{}1$. A brief comparison with the conductance spectr…
利用广义Landauer方法研究了锯齿形和扶手椅形介观石墨烯的非线性输运。我们发现，对于清洁系统，扶手椅边缘系统的低偏压低温电导G量子化为G/t=4 n e^2/h，而对于锯齿形边缘系统，量子化变为G/t=4（n+1/2）e^2/h，其中t是传输概率，n是整数。我们还研究了非零偏压、温度和磁场对电导的影响。在这些系统中的量子化平台的磁场依赖性是有点不同的二维电子气中发现由于不同的朗道能级量子化。
Over the last decade, interest in one-dimensional charge transport has progressed from the seminal discovery of Landauer quantization of conductance, as a function of carrier density, to finer-scale phenomena at the onset of quantization. This has come to be called the "0.7 anomaly", rather connoting a theoretical mystery of some profundity and universality, which remains open to date. Its somewhat imaginative appellation may tend to mislead, since the anomaly manifests itself over a range of conductance values: anywhere between 0.25 to 0.95 Landauer quanta. In this paper we offer a critique o…
In the present work the possibility of regulating local magnetic field in a quantum ring is investigated theoretically. The ring is coupled to a quantum wire and subjected to an in-plane electric field. Under a finite bias voltage across the wire a net circulating current is established in the ring which produces a strong magnetic field at its centre. This magnetic field can be tuned externally in a wide range by regulating the in-plane electric field, and thus, our present system can be utilized to control magnetic field at a specific region. The feasibility of this quantum system in designin…
We present phase coherence time measurements in quasi-one-dimensional mesoscopic wires made from high mobility two-dimensional electron gas. By implanting gallium ions into a GaAs/AlGaAs heterojunction we are able to vary the diffusion coefficient over 2 orders of magnitude. We show that in the diffusive limit, the decoherence time follows a power law as a function of diffusion coefficient as expected by theory. When the disorder is low enough so that the samples are semi-ballistic, we observe a new and unexpected regime in which the phase coherence time is independent of disorder. In addition…
We illustrate how classical chaotic dynamics influences the quantum properties at mesoscopic scales. As a model case we study semiclassically coherent transport through ballistic mesoscopic systems within the Landauer formalism beyond the so-called diagonal approximation, i.e. by incorporating classical action correlations. In this context we review and explain the two main trajectory-based methods developed for calculating quantum corrections: the configuration space approach and the phase space approach that can be regarded as less illustrative but more general than the first one.
Carrier mean free path and temperature imbalance in mesoscopic wires
在电场作用下，金属纳米线中的非相干电子输运表现出不同的前向和后向非平衡态载流子温度。取决于表征分支间载流子后向散射的平均自由程，传输机制在弹道极限和扩散极限之间变化。特别是，我们表明，同时测量的电气特性和载波分布函数提供了一种直接的方法来提取载波平均自由程，即使它是可比的导体长度。我们的模型与Pothier { \it et al.}对铜纳米线的实验工作符合得很好。[Phys. Rev. Lett. { \bf 79}，3490（1997）]，并提供了对局部载流子分布函数中观察到的不均匀热加宽及其随外部偏置的缩放的优雅解释。
The Landauer-Büttiker formalism provides a simple and insightful way for investigating many phenomena in mesoscopic physics. By this approach we derive general formulas for the energy properties and apply them to the basic setups. Of particular interest are the noise properties. We show that energy current fluctuations can be induced by zero-point fluctuations and we discuss the implications of this result.
我们在金线中测量了准粒子之间的能量交换率、准粒子的相位相干时间和电阻随温度的变化，以探讨低温下相关的相互作用过程。我们发现，能量交换率是高于预期的电子-电子相互作用的理论，它有一个不同的能量依赖性。失相时间在8 K ~ 0.5K之间是恒定的，低于0.5K时，失相时间增加。的磁阻是负的，在大的字段尺度，和电阻随温度的升高而降低，这表明磁性杂质的存在下，可能是Fe。而电阻率和相位相干测量可以归因于磁性杂质，提出的问题是，这些磁性杂质是否也可以调解准粒子之间的能量交换。
