NSLS-II Friday Lunchtime Seminar

"Quantum materials based on metamorphic InAsSb superlattices"

Presented by Sergey Suchalkin, Stony Brook University, Stony Brook, NY

Friday, June 28, 2019, 12:00 pm — NSLS-II Bldg. 743 Room 156

Recently proposed metamorphic InSbxAs1-x/InSbyAs1-y superlattices (SLs) manifest a new class of bulk materials where the bandgap can be tuned down to negative values [1,2]. Application of the virtual substrate approach relieves the limitation dictated by the substrate lattice constant and makes possible to grow materials with high crystalline quality in the entire range of alloy compositions. While remaining viable candidates to compete with the state-of-the-art mercury-cadmium-telluride (MCT) compound materials in the field of infrared detection and imaging, the new low-bandgap InAsSb SLs are new platform for investigation of intriguing physical phenomena such as the quantum spin Hall effect, and Majorana zero modes which has recently appeared in the searchlight of solid-state physics. I will present the latest results on experimental and theoretical analysis of carrier dispersion and band structure of short period metamorphic InSbxAs1-x/InSbyAs1-y superlattices, obtained in the Optoelectronics group of Stony Brook University. We demonstrate that the Dirac dispersion is realized in short period InAs1-x Sbx/InAs1-ySby metamorphic superlattices with the bandgap tuned to zero by adjusting the superlattice period and layer strain [3,4]. It was shown that the new material has anisotropic carrier dispersion: the carrier energy associated with the in-plane motion is proportional to the wave vector and characterized by the Fermi velocity vF, the dispersion corresponding to the motion in the growth direction is quadratic. Remarkably, the Fermi velocity in this system can be controlled by varying the overlap between electron and hole states in the superlattice [3]. We present a picture of modification of the energy spectrum due to variation of layer thicknesses, strain and composition of the SLs. The effects of dimensional quantization, tunneling and interface scattering on the SL band structure will be discussed. 1 - G. Belenky, D. Wang, Y. Lin, D. Donetsk

Hosted by: Ignace Jarrige

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