Wave packets in mesoscopic systems: From time-dependent dynamics to transport phenomena in graphene and topological insulators
Wave packets in mesoscopic systems: From time-dependent dynamics to transport phenomena in graphene and topological insulators
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介观系统中的波包：从时间相关动力学到石墨烯和拓扑绝缘体中的传输现象
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发表时间：
2013
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通讯作者：
V. Krückl
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作者：
V. Krückl
在世纪初，固态材料的范围是
通过具有手性自旋的电荷激发的晶体扩展，
接近费米能的赝自旋织构。如此卓越的电子
在石墨烯或拓扑绝缘体中可以找到这些特性，
为即将到来的电子设备提供了巨大的潜力。
在本论文中，
研究的时间依赖计划，其中描述了电子
波包传播的激发。时间演化
初始状态包含了各种动态观测量的信息，
这通常具有有趣的效果。例如，石墨烯经受
对于垂直磁场呈现出丰富的复兴结构，
导致了一系列的崩溃和复苏，
局部化状态上层建筑中产生的附加动力效应
所谓的布洛赫-齐纳振荡（Bloch-Zener oscillation），
由于电子和空穴之间的齐纳隧穿事件而产生
在一个布洛赫循环期间的分支。这导致更丰富的频率模式
并且在电流-电压特性中产生显著的迹线。
此外，动态观测量也可以转化为静态观测量，
物理性质，如态密度或传输幅度。
因此，通过介观系统传播的波包可以是
用于推导其静态散射特性。这是利用
研究收缩的开关功能，
碲化汞异质结构，它作为一个建筑块，
提出了一种新型的电荷自旋晶体管。此外，委员会认为，
碲化汞量子威尔斯阱的Berry相位效应
拓扑或常规绝缘体的研究，
像弱局域化一样扩散传输的特征。
At the beginning of 21th century, the range of solid state materials was
extended by crystals featuring charge excitations with a chiral spin or
pseudo-spin texture close to the Fermi energy. Such exceptional electronic
properties can be found in graphene or topological insulators, which both
render a great potential for upcoming electronic devices.
In this thesis, mesoscopic systems of such solid state materials are
investigated by a time-dependent scheme, which describes the electronic
excitations by the propagation of wave packets. The time evolution of an
initial state contains the information of various dynamical observables,
which often feature interesting effects. For example, graphene subjected
to a perpendicular magnetic field exhibits a rich revival structure,
leading to a periodic sequence of collapses and revivals of an initially
localized state. An additional dynamical effect arising in superstructures
of zero-gap semiconductors are so called Bloch-Zener oscillations, which
arise because of a Zener tunneling event between the electron and hole
branch during one Bloch cycle. This leads to a richer frequency pattern
and generates prominent traces in the current-voltage characteristics.
Furthermore, dynamical observables can also be transformed into static
physical properties, like density of states or transmission amplitudes.
Accordingly, a wave-packet propagating through a mesoscopic system can be
employed to derive its static scattering characteristics. This is utilized
to investigate the switching functionality of constrictions based on
mercury telluride heterostructures, which act as a building block for a
novel charge and spin-transistor presented in this thesis. Furthermore,
Berry phase effects of mercury telluride quantum wells acting as
topological or conventional insulators are studied with respect to
signatures in diffusive transport like weak localization.