Effect of temperature on resonant electron transport through stochastic conduction channels in superlattices
A. O. Selskii, A. A. Koronovskii, A. E. Hramov, O. I. Moskalenko, K. N. Alekseev, M. T. Greenaway, T. M. Fromhold, A. V. Shorokhov, N. N. Khvastunov, A. G. Balanov
We show that resonant electron transport in semiconductor superlattices with an applied electric and tilted magnetic field can, surprisingly, become more pronounced as the lattice and conduction electron temperature increases from 4.2 K to room temperature and beyond. It has previously been demonstrated that at certain critical field parameters, the semiclassical trajectories of electrons in the lowest miniband of the superlattice change abruptly from fully localised to completely unbounded. The unbounded electron orbits propagate through intricate web patterns, known as stochastic webs, in phase space, which act as conduction channels for the electrons and produce a series of resonant peaks in the electron drift velocity versus electric field curves. Here, we show that increasing the lattice temperature strengthens these resonant peaks due to a subtle interplay between thermal population of the conduction channels and transport along them. This enhances both the electron drift velocity and the influence of the stochastic webs on the current-voltage characteristics, which we calculate by making self-consistent solutions of the coupled electron transport and Poisson equations throughout the superlattice. These solutions reveal that increasing the temperature also transforms the collective electron dynamics by changing both the threshold voltage required for the onset of self-sustained current oscillations, produced by propagating charge domains, and the oscillation frequency.
Implication of the double-gating mode in hybrid photon counting detector for measurements of transient heat conduction in GaAs/AlAs superlattice structures
Resonant interlayer coupling in NbSe$_2$-graphite epitaxial moir{é} superlattices
SUPA, School of Physics and Astronomy, University of St Andrews（圣安德鲁斯大学物理与天文学学院）；Department of Physics and Astronomy, University of Manchester（曼彻斯特大学物理与天文学系）；Max Planck Institute for Chemical Physics of Solids（马克斯·普朗克固体化学物理研究所）；Physics Study Program, Faculty of Science and Technology, Syarif Hidayatullah State Islamic University Jakarta（雅加达希达亚图拉伊斯兰国立大学科技理学院物理学专业）；Institute for Materials Research, Tohoku University（东北大学材料科学研究所）
Thermal conductivity of GeTe/Sb$_{2}$Te$_{3}$ superlattices measured by coherent phonon spectroscopy
利用飞秒相干声子谱研究了GeTe/Sb $_{2}$ Te $_{3}$超晶格的晶格热导率。在非晶和晶态GeTe/$_{2}$ SL薄膜中获得的时间分辨瞬态反射率在太赫兹（THz）频率下具有皮秒退相时间的相干$A_{1}$光学模式。基于德拜理论，我们计算了晶格热导率，包括晶界散射、点缺陷散射、umklapp过程和声子共振散射。结果表明，在非晶SL的热导率是较小的温度依赖性，归因于占主导地位的声子缺陷散射。
Interband characterization and electronic transport control of nanoscaled GeTe/Sb$_2$Te$_3$ superlattices
相变材料中晶体到非晶转变的非凡电子和光学性质导致了存储器应用的重要发展。一个有前途的前景是提供纳米尺度的相变结构。沿着这条研究路线，我们研究了纳米级GeTe/Sb $_2$ Te $_3$硫系超晶格薄膜的带间光透射谱。我们确定，不同的堆叠顺序和生长方法的薄膜，的自由电子的密度和散射时间，以及价到导电过渡的特性。研究发现，当子层厚度低于$\sim$ 3 nm时，自由电子密度随着GeTe含量的增加而降低。简单的能带模型分析表明GeTe和Sb $_2$ Te $_3$层混合，形成标准的GeSbTe合金缓冲层。我们表明，它是可能的，通过适当地选择沉积层的厚度来控制薄膜的电子输运性质，我们推导出一个模型，为任意的薄膜堆叠。
Observation of high-temperature quantum anomalous Hall regime in intrinsic MnBi$_2$Te$_4$/Bi$_2$Te$_3$ superlattice
量子反常霍尔效应是拓扑非平凡系统在零磁场中的一种基本输运响应。它的物理起源依赖于本质上反转的电子能带结构和铁磁性，其最重要的表现是边缘的手性电荷电流的无耗散流动，这可能会改变未来的量子电子学。在这里，我们报告了一个以前未知的贝里曲率驱动的异常霍尔制度（“Q窗口”）在上述开尔文温度的磁性拓扑体晶体，通过生长Mn离子自组织成周期有序的MnBi $_2$ Te $_4$ /Bi $_2$ Te $_3$超晶格。强大的铁磁性的MnBi $_2$ Te $_4$单层打开一个大的表面间隙，和异常霍尔电导达到一个$e^2/h$量子化平台时，费米能级被调谐到这个间隙内的Q-窗口，其中异常霍尔电导从散装是一个高精度为零。在这个新的制度的量子化是不阻碍的散装传导通道，因此应该存在于一个广泛的家庭的拓扑磁体。
Phonon Scattering Mechanism in Thermoelectric Materials Revised via Resonant X-ray Dynamical Diffraction
热电材料的工程需要理解晶格和电子自由度的热传导。填充方钴矿表示适合于热电应用的材料的大家族，其中减少的晶格热传导归因于结构的大笼内的填料阳离子的局部低频振动（嘎嘎声）。本文提出了一种利用X射线在CeFe $_4$ P $_{12}$单晶中的动态衍射的多波长方法，并将其应用于求解原子振动的振幅。结果表明，整个填充笼系统的振动动力学是热电性能优化背后的实际活动机制。
