Sponsored by NSF DMR-0507866

1. b) a) Carrier and Spin Dynamics in InSb- and InMnSbBased Heterostructures, Gita A. Khodaparast, Virginia Polytechnic Institute and State University, DMR 0507866 • In recent years, probing and manipulations of spins in semiconductors have attracted considerable interest because of its potential applications in “spintronic” devices. In this path, narrow gap semiconductors (NGS) such as InSb based material systems have been under-represented. However, these materials are likely to play an important role due to their unique properties which lead to considerable spin splitting without applying external magnetic fields [Ref. 1,2]. • One of the key challenges in developing spin based devices is to generate, control, and measure spin polarized current directly. Several measurements on material systems such as n-type InAs, as shown in Fig. 1a [Ref. 3], demonstrated optical generation of spin polarized current. One major advantage of using materials such as InSb, can be in the magnitude of the generated current due to their larger spin-orbit couplings compared to several other III-V semiconductors. As demonstrated in Fig. 1 b, we recently measured photo-induced current in InSb quantum wells (QW), provided by group of Prof. Santos at the Univ. of Oklahoma. The magnitude of the current is several orders larger than the observations in Al0.25Ga0.75N/GaN, InAs/AlGaSb, and GaAs/AlGaAs [Ref. 3-6]. Fig. 1: a) Spin polarized current in n-type InAs as a function of the incident light helicity,. The extremes occur at 45 and 135 degrees [Ref. 3]. b) Spin polarized current in an InSb QW at 77 K as a function of retardation in wavelength with the step size of 0.01. The extremes are at ±/4 with some asymmetric pattern. [Ref. 1]:K. Nontapot, el al., Cond-Mat.Mtrl-Sci [arXiv.0807.2660v] [Ref. 2]:G. A. Khodaparast, et al., Phys. Rev. B 70, 155322 (2004). [Ref. 3]: S. D. Ganichev and W. Prettl, J. Phys: Condens. Matter 15 (2003) R935. [Ref.4 ]: K. S. Cho, et al., Phys. Rev. B 75, 085327 (2007). [Ref. 5]: V. V. Bel'kov, et al.,Solid State Commun. 128, 283 (2003). [Ref. 6]: L. Yang, et al., Phys. Rev. Lett. 96, 186605 (2006).

2. Group of Prof. Khodaparast at the Physics Department,Virginia Tech.Gita A. Khodaparast, Virginia Polytechnic Institute and State University, DMR 0507866 Educational activities: My group has attracted four PhD students, one Masters student (Ms Aliya Gifford, currently at John Hopkins Univ.), and seven undergraduate students. My students’ summer undergraduate research activities have been partially supported by the NSF-REU supplement. One of my undergraduate students, Ms. Ariana Reese, joined my group this summer from a historically black university in Virginia, Norfolk State, and I plan to continue my connection with this school. My group hosted two high schools students in summer of 2006 and 2007. Outreach: Starting lectures on nano-science and nano-technology at the Roanoke Governor’s school this fall. Students from several remote districts attend this school to take their math and science classes. In concert with these lectures, internet-based tutorialswill be developedthat can be accessed not only by high school students but also by learners and educators who do not have access to the traditional university system. My activity was highlighted in the school’s parent newsletter on 11-26-07: (http://www.rvgs.k12.va.us/parents/). Ariana Reese, a summer undergraduate student from Norfolk State is learning how to use a fluorescence microscope. Kanokwan Nontapaot, a PhD student, is cooling an MCT detector to perform time resolved spectroscopy using a mid-infrared laser. She is graduating this summer. Sponsored by NSFDMR-0507866 Undergraduate summer research was supported partially by NSF-REU supplement.