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Condensed Matter Theory Group Seminar
Valleytronics in Silicon: the Principles and the Practice
Date: Monday, February 24th
Time: 4:30 pm
Place: Chamberlin 5310
Speaker: Andre Saraiva, University of Wisconsin
Abstract: Alternative schemes for information processing are being pursued by the industry. Spintronics - the most prominent candidate for alternative electronics - explores an internal degree of freedom of electrons, namely the spin, in order to encode information. Recent advances in the manipulation of the valley degree of freedom[1] of certain semiconductors are opening the possibility for a third option: Valleytronics. But in order to achieve useful control of valley, large enough valley-orbit induced valley splitting (VS) must be achieved.

We will present three ways to control valleys on a scale higher than 1 meV:

a) in a quantum well, the adoption of a barrier constituted of a layered heterostructure might lead to constructive reflection if the layer thicknesses match the electron wavelength, in analogy with a Bragg mirror [2];

b) the disparity between the high valley splitting in a impurity donor potential and the low splitting in a Si/Insulator interface may be harnessed controlling the tunneling between these two states, so that the valley splitting may be controlled digitally [3];

c) intrinsic Tamm/Shockley interface states might strongly hybridize with conduction states, leading to a much enhanced valley splitting[4,5], and its contribution to the 2DEG ground state may be experimentally identified [6].

1. D. Culcer, A. L. Saraiva, Belita Koiller, Xuedong Hu, and S. Das Sarma, PRL *108*, 126804 (2012).
2. L. Zhang, J.-W. Luo, A Saraiva, Belita Koiller, Alex Zunger, Nature Comm. *4*, 2396 (2013)
3. A. Baena, A. L. Saraiva, Belita Koiller, and M. J. CalderA3n, PRB 86, 035317 (2012).
4. K. Takashina, Y. Ono, A. Fujiwara, Y. Takahashi and Y. Hirayama, *PRL* *96, *236801 (2006).
5. A. Saraiva, Belita Koiller and M. Friesen, Phys. Rev. B *82*, 245314 (2010).
6. A. Dusko, A. Saraiva and Belita Koiller, arXiv:1310.6878 (2013).
Host: Perkins
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