A Magneto-Stark Effect and Exciton Motion in CdS
A Magneto-Stark Effect and Exciton Motion in CdS
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DOI：
10.1103/physrev.124.657
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发表时间：
1961-11
期刊：
影响因子：
--
通讯作者：
D. G. Thomas;J. Hopfield
中科院分区：
文献类型：
--
作者：
D. G. Thomas;J. Hopfield
对于弱激子线，激子吸收发生在能量为具有等于介质中的光的波矢的激子的能量的能量处。这些激子具有有限的波矢，因此具有有限的速度。在均匀磁场中，由于质心速度引起的电子和空穴上的洛伦兹力产生了除了通常考虑的那些之外的磁扰动。这种微扰的测量测量已知波矢的激子的速度，因此确定总激子质量。此外，依赖于激子速度的这种效应的测量提供了激子吸收线和由于杂质引起的吸收线之间的正区别。它表明，这种扰动可以通过测量的斯塔克效应的激子在均匀磁场的存在下测量。用这种方法测量了CdS顶价带中n=2$态激子的激子质量，其值为0.92\ifmmode\pm\else\textpm\fi{}0.18，与独立实验计算的质量相当吻合.还研究了在没有磁场的情况下的斯塔克效应，以确保理解在磁场存在下的效应。磁场中的斯塔克效应有时会表现出特殊的行为，这归因于外部霍尔场。这种解释给出了在1.6K和31000高斯下，“好”CdS晶体中电子的${\ensuremath {\omega}}_{c}{\ensuremath {\tau}}_{r}\ensuremath{\approx}2$的估计。
Exciton absorption occurs, for weak exciton lines, at an energy which is the energy of an exciton having a wave vector equal to that of the light in the medium. These excitons have a finite wave vector, and therefore, a finite velocity. In a uniform magnetic field, the Lorentz force on the electron and hole due to the center-of-mass velocity produces a magnetic perturbation in addition to those ordinarily considered. The measurement of such a perturbation measures the velocity of an exciton of known wave vector, and therefore determines the total exciton mass. In addition, the measurement of this effect which depends on the exciton velocity provides a positive distinction between exciton absorption lines and absorption lines due to impurities. It is shown that this perturbation can be measured by the measurement of the Stark effect on excitons in the presence of a uniform magnetic field. The exciton mass for the $n=2$ states of excitons formed from the top valence band in CdS was measured by this technique, and found to be 0.92\ifmmode\pm\else\textpm\fi{}0.18 in reasonable agreement with the mass calculated from independent experiments. The Stark effect in the absence of a magnetic field was also studied to ensure an understanding of the effect in the presence of a magnetic field. The stark effect in a magnetic field sometimes exhibits peculiar behavior which was attributed to an extraneous Hall field. This interpretation gives an estimate of ${\ensuremath{\omega}}_{c}{\ensuremath{\tau}}_{r}\ensuremath{\approx}2$ for electrons in "good" CdS crystals at 1.6\ifmmode^\circ\else\textdegree\fi{}K and at 31 000 gauss.