Nonlinear dynamics of impurity states in semiconductors driven by intense THz pulses

强太赫兹脉冲驱动的半导体中杂质态的非线性动力学

• 批准号: 411486076
• 负责人: Professor Dr. Hartmut G. Roskos
• 金额: --
• 依托单位: Physikalisches Institut
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/411486076?language=en
• 关键词: Nonlinear; dynamics; impurity; states; semiconductors

Shallow dopant impurities, which provide the mobile charges in room-temperature semiconductors devices, take on a new role at low temperature, where the excess charges are instead bound to their parent ions with a set of states analogous to gas-phase atoms.Besides their potential for quantum information technology, such “quasi-atoms” can offer a unique platform for studying intense light-matter interactions, bridging the gap between high-field ultrafast phenomena in free atoms and bulk semiconductors.Due to the strong interaction with the host lattice, the photon energy scale of the impurity states is shifted from the ultraviolet (for gas atoms) down to the terahertz (THz) range, with binding fields of kV/cm and spatial extent of several nanometers. Moreover, the impurity states depend on both dopant and host species, resulting in a whole family of quasi-atoms with orbital and spin densities which deviate from a simple hydrogen model. The host interactions also confront key aspects in solid-state physics, such as the effect of phonon interactions, which have a profound effect on the lifetimes and dephasing of the excited states.Here we employ experiments with intense THz pulses to study of the non-linear response of donor/acceptor impurities in conventional semiconductor hosts (Si, Ge, GaAs).Two key phenomena can be observed: (i) the dynamic Stark (Autler-Townes) effect and quantum interference between states, and (ii) higher-harmonic generation (HHG) following tunnel ionization due to the subsequent acceleration of carriers in the THz field.Here we employ a complementary approach with both single-cycle THz pulses (in our laboratory) and multi-cycle THz pulses (in free-electron-laser facilities). The multi-cycle pulses allow a more conventional state-selective excitation and a system that can be described in terms of field-dressed (Floquet) states, whereas broadband excitation with single-cycle pulses allows one to measure the ultrafast evolution directly in the time domain and to probe for propagation effects. It also opens the possibility to control the resulting quantum state via pulse shaping.The experiments also further the application of four-wave-mixing pump-probe methodology in the THz range to the study of quantum systems, which has only recently become accessible with femtosecond laser systems. While the HHG observed from such impurities has its origin in the ionization of bound states and the emission is due to the subsequent acceleration of the carriers, analogous to the situation studied intensely for gas-phase atoms, the acceleration takes place in the adjacent semiconductor band(s), as per recent studies of HHG in bulk semiconductors with intense mid-infrared excitation. Our experimental findings will hence further unify these two existing fields.

浅掺杂杂质在室温半导体器件中提供移动电荷，在低温下发挥新作用，其中多余的电荷以一组类似于气相原子的状态与其母离子结合。这种“准原子”具有量子信息技术的潜力，可以为研究强烈的光与物质相互作用提供一个独特的平台，弥合自由原子和体半导体中高场超快现象之间的差距。在主晶格中，杂质态的光子能量尺度从紫外（对于气体原子）转移到太赫兹（THz）范围，结合场为kV/cm，空间范围为几纳米。取决于掺杂剂和主体物种，导致整个准原子家族的轨道和自旋密度偏离了简单的氢模型，主体相互作用也面临着关键方面。固态物理，例如声子相互作用的影响，对激发态的寿命和相移有深远的影响。在这里，我们采用强太赫兹脉冲实验来研究供体/受体杂质的非线性响应传统半导体主体（Si、Ge、GaAs）。可以观察到两个关键现象：（i）动态斯塔克（奥特勒-汤斯）效应和态之间的量子干涉，以及（ii）以下高次谐波产生（HHG）由于太赫兹场中载流子的后续加速而产生隧道电离。在这里，我们采用单周期太赫兹脉冲（在我们的实验室）和多周期太赫兹脉冲（在自由电子激光设施中）的补充方法。脉冲允许更传统的状态选择性激励和一个可以用现场装饰（Floquet）状态来描述的系统，而单周期脉冲的宽带激励允许人们直接测量超快演化。它还提供了通过脉冲整形控制所得量子态的可能性。这些实验还进一步将太赫兹范围内的四波混合泵浦探针方法应用于量子系统的研究。 ，最近才通过飞秒激光系统实现，而从此类杂质中观察到的 HHG 起源于束缚态的电离，并且发射是由于载流子的随后加速而产生的，类似于对气体的深入研究的情况。阶段根据最近对具有强烈中红外激发的块状半导体中 HHG 的研究，加速发生在相邻的半导体能带中。我们的实验结果将进一步统一这两个现有领域。