共查询到14条相似文献,搜索用时 62 毫秒
1.
2.
采用散射矩阵方法,研究了在应力自由和硬壁两种典型的边界条件下含半圆弧形腔的量子波导中声学声子输运和热导性质.结果表明在两种边界条件下声子透射谱和热导有着不同的特征.在应力自由边界条件下,能观察到普适的量子化热导现象,当结构为一理想的量子线时,在低温区域有一个量子化平台出现,而当半圆弧形结构存在时,非均匀横向宽度引发的弹性散射使得量子化平台被破坏;在硬壁边界条件下,不可能观察到量子化热导现象,热导随温度的增加单调上升;计算结果表明还可以通过调节半圆弧形结构的半径来调控声子的输运概率和热导.
关键词:
声学声子输运
热导
量子体系 相似文献
3.
利用弹性近似模型和散射矩阵方法,研究了低温下多通道量子结构中的弹性声学声子输运的性质. 计算结果表明,对于低频声学声子,只要通道的横向宽度相同,各通道中最低阶模的透射概率几乎不受其他结构参数的影响,且其数值都接近于0.25;而高频声学声子在各通道中的透射概率与结构参数密切相关,不同通道中的透射概率不同;当温度非常低时,各通道的热导都接近于量子化热导π2k2BT/(3h)的四分之一;随着温度的升高,各通道的热导增减
关键词:
声学声子输运
热导
量子结构 相似文献
4.
5.
采用非平衡格林函数方法, 在保持总的能量输出通道中石墨链数不变的条件下, 研究并比较了并列的石墨纳米带通道中弹性声学声子输运和热导特性. 结果表明, 能量输出通道的增加能降低每个能量输出通道的热导; 与能量输入热库最近的能量输出通道热导最大, 最远的能量输出通道热导最小; 中间能量输出通道的热导性质与并列的各输出通道的结构参数密切相关, 最近和最远的能量输出通道的热导性质仅与各自能量输出通道的结构参数有关; 粗糙边缘结构能有效调节各通道的热导; 总的热导性质与能量输出通道石墨链数、能量输出通道数以及边缘结构粗糙程度密切相关. 相似文献
6.
张剑华 《原子与分子物理学报》2011,28(4)
研究了异侧非重叠三封闭端量子波导中的声学声子传输和热导率性质.结果表明:由于激发模的产生,总传输系数在整数约化频率的时发生跳跃;各个激发模所产生的温度条件不一样,温度越高,被激发的模越多,并且高阶模对热导的影响较小;声子传输和热导性质与不连续结构的形状和位置有直接的关系,声子传输和热导性质对量子线的温度环境相当敏感. 相似文献
7.
张剑华 《原子与分子物理学报》2011,28(6):703-709
研究了异侧非重叠三封闭端量子波导中的声学声子传输和热导率性质。结果表明:由于激发模的产生,总传输系数在整数约化频率的时发生跳跃;各个激发模所产生的温度条件不一样,温度越高,被激发的模越多,并且高阶模对热导的影响较小;声子传输和热导性质与不连续结构的形状和位置有直接的关系,声子传输和热导性质对量子线的温度环境相当敏感。 相似文献
8.
利用非平衡格林函数方法研究了石墨纳米带中三空穴错位分布对热输运性质的影响.研究结果发现:三空穴竖直并排结构对低频声子的散射较小,导致低温区域三空穴竖直并排时热导最大,而在高频区域,三空穴竖直并排结构对高频声子的散射较大,导致较高温度区域三空穴竖直并排时热导最小;三空穴的相对错位分布仅能较大幅度地调节面内声学模高频声子的透射概率,而三空穴的相对错位分布能较大幅度地调节垂直振动膜高频声子和低频声子的透射概率,导致三空穴的相对错位分布不仅能大幅调节面内声学模和垂直振动模的高温热导,也能大幅调节垂直振动模的低温热导.研究结果阐明了空穴位置不同的石墨纳米带的热导特性,为设计基于石墨纳米带的热输运量子器件提供了有效的理论依据. 相似文献
9.
在连续弹性近似下,采用转移矩阵方法,研究了由不同含Al浓度的异质结(GaAs/AlxiGa1-xiAs)所构成的对称多层异质结构中的声学声子输运性质.结果表明:该结构中的声子透射谱具有与同组分厚度超晶格(GaAs/AlAs )不一样的特征,具体体现在透射曲线振荡幅度与频率等方面;声子透射谱特征与对称异质结构中AlxiGa1-xiAs层的含Al浓度xi(i表示对称轴两边的第i层)的分布有很大的关系,具体表现为:当xi随i的增加而递减时,透射谱线除主波谷外较平滑;而当xi随i的增加而递增时,透射谱振荡明显增大,且主波谷被分裂.声子透射系数还依赖于异质结组分层的厚度,尤其是AlxiGa1-xiAs的厚度.另外,异质结的层数对声子输运也产生一定的影响.
关键词:
输运
声子
异质结 相似文献
10.
11.
Using the scattering-matrix method, we investigate the thermal conductance in a two-slit quantum waveguide at low temperature. The results show that the total thermal conductance decreases monotonically with temperature increasing. Moreover, we find that the behaviours of the thermal conductance versus temperature are different for different types of slits. 相似文献
12.
《Physics letters. A》2014,378(30-31):2195-2200
We study the ballistic phonon transport and thermal conductance of six low-lying vibration modes in quantum wire modulated with quantum dot at low temperatures. A comparative analysis is made among the six vibrational modes. The results show that the transmission rates of the six vibrational modes relative to reduced frequency display periodic or quasi-periodic oscillatory behavior. Among the four acoustic modes, the thermal conductance contributed by the torsional mode is the smallest, and the thermal conductances of other acoustic modes have adjacent values. It is also found that the thermal conductance of the optical mode increases from zero monotonously. Moreover, the total thermal conductance in concavity-shaped quantum structure is lower than that in convexity-shaped quantum structure. These thermal conductance values can be adjusted by changing the structural parameters of the quantum dot. 相似文献
13.
Ling-Jiang Yao Lingling Wang Xiao-Fang Peng B.S. Zou Ke-Qiu Chen 《Physica E: Low-dimensional Systems and Nanostructures》2008,40(9):2862-2868
We investigate the thermal conductance in a quantum waveguide modulated with quantum dots at low temperatures. It is found that the thermal conductance sensitively depends on the geometrical parameters of the structure and boundary conditions. When the stress-free boundary conditions are applied in the structure, the universal quantum of thermal conductance can be found regardless of the geometry details in the limit T→0. For an uniform quantum waveguide, a thermal conductance plateau can be observed at very low temperatures; while for the quantum waveguide modulated with quantum dots, the plateau disappears, instead a decrease of the thermal conductance can be observed as the temperature goes up in the low temperature region, and its magnitude can be adjusted by the radius of the quantum dot. Moreover, it is found that the quantum waveguide with two coupling quantum dots exhibits oscillatory decaying thermal conductance behavior with the distance between two quantum dots. However, when the hard-wall boundary conditions are applied, the thermal conductance displays different behaviors. 相似文献
14.
Using the scattering matrix method, we investigate the thermal conductance associated with ballistic phonons at low temperatures
in asymmetric quantum structures. The results show that when the structure is an ideal quantum wire, the universal value π
2
κ
B2(3h) can be observed at very low temperatures. However, for asymmetric quantum structure, the thermal conductance is less than
the universal value π
2
κ
B2(3h), even at T → 0. The results also show that the thermal conductance is strongly dependent on the transport direction. The rectification
effect can be observed in the asymmetric structure and can be adjusted by changing the structural parameters. A brief analysis
of these results is given.
相似文献