Collaborative Research: Carrier Dispersion and Nontrivial Topological Phases in Ultra-Low Bandgap Metamorphic InAsSb Ordered Alloys

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Semiconductors suitable for the development of infrared opto-electronic devices attract attention of physicists and engineers for many years. Metamorphic molecular beam epitaxy, a novel technology for material development, produces high quality compounds with precise control of their composition (indium, arsenic, aluminum and antimony) over a wide range of atomic concentrations. This ability allows deep studies of the "quantum" properties of important narrow-band semiconductors that are protected against material imperfections. These properties may have profound implication for the performance of a variety of devices including quantum computers. In this project the interdisciplinary research team from Stony Brook University and Georgia Institute of Technology plans to use novel materials for experimental demonstration of intriguing features of quantum physics. The efforts combine development of new materials and study of their physical properties and energy spectra by a variety of advanced experimental techniques. The project also provides for synergetic training of graduate students in physics, material science, and engineering, creating research opportunities for undergraduate students. The K-12 education component aims at cultivating an early-stage awareness of using new materials and technologies to improve the device performance without compromising the quality of human life.This project is to carry out epitaxial growth of high-quality indium arsenide antimonide (InAsSb) alloys with controllable nanoscale ordering and to investigate the manifestations of the new topologically nontrivial phases in these materials. The material growth is based on a recently developed virtual substrate approach, which lifts the constraint from the substrate lattice constant. The physical properties of the InAsSb ordered alloys can then be controlled to an exceptional degree, via varying the lattice constant, the strain, the alloy composition, and the composition modulation period. With these new materials, the research team intends to answer the following fundamental questions. (1) Can nontrivial topological phases be realized and observed in metamorphic InAsSb alloys with nanoscale ordering and tunable bandgap? (2) Can the InAsSb ordered alloys be a new platform for demonstration of Majorana zero mode? These topics are of great fundamental and technological interest, particularly for the solid-state realization of topological quantum computing. The technical approaches of the project include band structure calculation, advanced epitaxial growth, and cutting-edge characterization methods. The latter features transmission electron microscopy, high-resolution x-ray diffraction, reciprocal space mapping, infrared spectroscopy in high magnetic fields, and angle-resolved photoemission spectroscopy. Graduate and undergraduate students participating in the project have unique opportunities to master these methods and engage in all stages of the material development process.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.