We study the conductance of disordered graphene superlattices with short-range structural correlations. The system consists of electron- and hole-doped graphenes of various thicknesses, which fluctuate randomly around their mean value. The effect of the randomness on the probability of transmission through the system of various sizes is studied. We show that in a disordered superlattice the quasiparticle that approaches the barrier interface almost perpendicularly transmits through the system. The conductivity of the finite-size system is computed and shown that the conductance vanishes when the sample size becomes very large, whereas for some specific structures the conductance tends to a nonzero value in the thermodynamics limit.
Crossover of conductance and local density of states in a single-channel disordered quantum wire
计算了具有手征对称性的单沟道无序量子线在两种不同几何结构下的介观局域态密度的概率分布。提出了一种近似的解析法来描述单沟道无序量子线的电导和LDOS的概率分布在手征对称类和标准对称类之间的交叉。通过与Schomerus和Titov在Phys. Rev. B \textbf{67}，100201（R）（2003）中引入的大偏差分析法进行比较，讨论了该分析法的准确性。
Recently, moiré superlattices have attracted considerable attentions because they are found to exhibit intriguing electronic phenomena of tunable Mott insulators and unconventional superconductivity. These phenomena are highly related to the physical mechanism of the interlayer coupling. However, up to now, there has not existed any theory that can completely interpret the experimental results of the interlayer conductance of moiré superlattice. In order to solve this problem, the superposition of periods and the corresponding coherence, which are the essential characteristics of moiré superla…
Electron dynamics in intentionally disordered semiconductor superlattices
我们研究了无序量子阱半导体超晶格的动力学行为，其中无序是有意的和短程关联的。我们发现，而一个粒子的传输时间的增长与井的数量在一个通常的无序超晶格的入射粒子能量的任何值呈指数关系，对于特定的入射能量值，这个时间线性增加时，包括相关的障碍。正如预期的那样，这些能量值与Dom \em et al.} [Phys. Rev. B { \bf 51}，14，359（1994）];在我们的动力学结果中看到这样的状态表现出弹道状态，非常接近完美超晶格的WKB近似。对入射高斯波包的输出信号进行傅里叶变换，揭示了原始信号的戏剧性滤波，这使我们相信，基于此属性的设备可以被设计并用于纳米技术应用。考虑到使用直流电场来抑制输出频带的可能性，我们也讨论了这一点。在结论中，我们总结了我们的结果，并提出了未来的发展前景，从这项工作。
Using Chebyshev polynomials, we study the electronic transport properties of massless Dirac fermions in symmetrical graphene superlattice composed of three regions. Matching wavefunctions and using transfer matrix method, we explicitly determine transmission probability as well as the conductance and Fano factor. At vertical Dirac points, we numerically find that the transmission probability shows transmission gaps, conductance has minimums and Fano factor has maximums.
A transfer matrix approach is used to study the electronic transport in graphene superlattices with long-range correlated barrier spacements. By considering the low-energy electronic excitations as massless Dirac fermions, we compute by transmission spectra of graphene superlattices with potential barriers having spacements randomly distributed with long-range correlations governed by a power-law spectral density $S(k)\propto 1/k^α$. We show that at large incidence angles, the correlations in the disorder distribution do not play a significant role in the electronic transmission. However, long…
We study the intrinsic and extrinsic Hall effects in disordered magnetic Weyl semimetals numerically. We show that in Weyl metals, where the Fermi energy deviates from the Weyl point, the Hall and longitudinal conductances exhibit a specific relation, which is distinguished from the well-known relation in integer quantum Hall systems. Around the Weyl point, the Hall conductance increases with increasing longitudinal conductance. This increasing behavior indicates the existence of additional contributions to the Hall conductance from the subbands of Weyl cones besides that from the bulk Berry c…
Many-body localization (MBL) has attracted significant attention due to its immunity to thermalization, role in logarithmic entanglement entropy growth, and opportunities to reach exotic quantum orders. However, experimental realization of MBL in solid-state systems has remained challenging. Here we report evidence of a possible phonon MBL phase in disordered GaAs/AlAs superlattices. Through grazing-incidence inelastic X-ray scattering, we observe a strong deviation of the phonon population from equilibrium in samples doped with ErAs nanodots at low temperature, signaling a departure from ther…
We study heat conduction mediated by longitudinal phonons in one dimensional disordered harmonic chains. Using scaling properties of the phonon density of states and localization in disordered systems, we find non-trivial scaling of the thermal conductance with the system size. Our findings are corroborated by extensive numerical analysis. We show that a system with strong disorder, characterized by a `heavy-tailed' probability distribution, and with large impedance mismatch between the bath and the system satisfies Fourier's law. We identify a dimensionless scaling parameter, related to the t…
The elastic collective modes of a moiré superlattice arise not from vibrations of a rigid crystal but from the relative displacement between the constituent layers. Despite their similarity to acoustic phonons, these modes, called phasons, are not protected by any conservation law. Here, we show that disorder in the relative orientation between the layers and thermal fluctuations associated with their sliding motion degrade the propagation of sound in the moiré superlattice. Specifically, the phason modes become overdamped at low energies and acquire a finite gap, which displays a universal de…
Magnetic silicene superlattices (MSSLs) are versatile structures with spin-valley polarization and tunneling magnetoresistance (TMR) capabilities. However, the oscillating transport properties related to the superlattice periodicity impede stable spin-valley polarization states reachable by reversing the magnetization direction. Here, we show that aperiodicity can be used to improve the spin-valley polarization and TMR by reducing the characteristic conductance oscillations of periodic MSSLs (P-MSSLs). Using the Landauer-Büttiker formalism and the transfer matrix method, we investigate the spi…
The valley transport properties of a superlattice of out-of-plane Gaussians deformations are calculated using a Green's function and a Machine Learning approach. Our results show that periodicity significantly improves the valley filter capabilities of a single Gaussian deformation, these manifest themselves in the conductance as a sequence by valley filter plateaus. We establish that the physical effect behind the observed valley notch filter is the coupling between counter-propagating transverse modes; the complex relationship between the design parameters of the superlattice and the valley …
