CAJ | 학술논문

微带超晶格在磁场和太赫兹场调控下表现出丰富而复杂的动力学行为，研究微带电子在外场作用下的输运性质对于太赫兹器件设计与研制具有重要意义。本文采用准经典的运动方程描述了超晶格微带电子在沿超晶格生长方向(z方向)的THz场和相对于z轴倾斜的磁场共同作用下的非线性动力学特性。研究表明，在太赫兹场和倾斜磁场共同作用下，超晶格微带电子随时间的演化表现出周期和混沌等新奇的运动状态。采用庞加莱分支图详细研究了微带电子在磁场和太赫兹场调控下的运动规律，给出了电子运行于周期和混沌运动状态的参数区间。在电场和磁场作用下，微带电子将产生布洛赫振荡和回旋振荡，形成复杂的协同耦合振荡。太赫兹场与这些协同振荡模式之间的相互作用是导致电子表现出周期态、混沌态以及倍周期分叉等现象的主要原因。
미대초정격재자장화태혁자장조공하표현출봉부이복잡적동역학행위，연구미대전자재외장작용하적수운성질대우태혁자기건설계여연제구유중요의의。본문채용준경전적운동방정묘술료초정격미대전자재연초정격생장방향(z방향)적THz장화상대우z축경사적자장공동작용하적비선성동역학특성。연구표명，재태혁자장화경사자장공동작용하，초정격미대전자수시간적연화표현출주기화혼돈등신기적운동상태。채용방가래분지도상세연구료미대전자재자장화태혁자장조공하적운동규률，급출료전자운행우주기화혼돈운동상태적삼수구간。재전장화자장작용하，미대전자장산생포락혁진탕화회선진탕，형성복잡적협동우합진탕。태혁자장여저사협동진탕모식지간적상호작용시도치전자표현출주기태、혼돈태이급배주기분차등현상적주요원인。
Vertical electron transport in semiconductor superlattice has been the focus of science and technology during the past two decades due to the potential application of superlattice in terahertz devices. When driven by electromagnetic field, many novel phenomena have been found in superlattice. Here we study the chaotic electron transport in miniband superlattice driven by dc+ac electric fields along the growth axis (z-axis) and a magnetic field tilted to z-axis using semiclassical equations of motion in the presence of dissipation. We calculate the electron momentum by changing the magnetic field or amplitude of the terahertz field. It is shown that the momentum py (t) of miniband electron exhibits complicated oscillation modes while changing the control parameters. Poincaré bifurcation diagram and power spectrum are adopted to analyze the nonlinear electron states. Poincaré bifurcation diagram is obtained by plotting pym =py (mTac) (with m=1, 2, 3, · · · and Tac the period of ac terahertz field) as functions of ac amplitude E1 after the transients decay. The periodic and aperiodic regions can be distinguished from each other since there are a large number of points in the chaotic regions. When the magnetic field is increased from 1.5 to 2 T, the Poincaré bifurcation diagram changes dramatically due to the strong effect of magnetic field on electron motion. The oscillating state of py (t) may be changed between periodic and chaotic syates. Power spectra of electron momentum py for different values of E1(= 2.06, 2.18, 2.388, and 2.72) are calculated for a deep insight into the nonlinear oscillating mode. It is found that the power spectra of n-periodic states show peaks at frequencies ifac/n (with i=1, 2, 3, · · · ); the power spectra of chaotic states are very irregular with a large number of peaks. We demonstrate that the dissipation and resonance between Bloch oscillation frequency and cyclotron frequency play an important role in the electron transport process. We attribute the emerging of periodic and chaotic states in a superlattice to the interaction between terahertz radiation and internal cooperative oscillating mode related to Bloch oscillation and cyclotron oscillation. In the case ofωB?=iωc, the time-dependent electron motion is chaotic in most regions of the parameter space. Results of the present paper are useful for designing terahertz devices based on the semiconductor superlattices.