The continuing evolution of sensor technology requires innovative approaches for reducing power consumption and improving sensitivity, resolution & operating temperature. The recent discovery of axion electromagnetic coupling in topological insulators holds great promise for drastic improvement of performance in sensor technology. This new class of materials has a bulk insulating energy gap and gapless Dirac-cone surface states which are protected by time-reversal symmetry. Unlike in traditional semiconductors, back-scattering is prohibited because of unique spin transport on the surfaces, leading to exciting non-dissipative applications. The striking electromagnetic coupling and half-integer quantum Hall effects open up completely new and revolutionary applications in nanoelectronics and spintronics. This project proposes to exploit the axion electromagnetic coupling effect in topological insulators and to build ultra-sensitive magnetic sensors that surpass the performance of traditional magnetometers.
Intellectual Merit: The intellectual merit of this project includes (i) the demonstration of the intriguing electromagnetic coupling effect in topological insulators that has not yet been experimentally explored; (ii) the improved understanding of material properties including magnetic doping of surfaces, and the growth of heterostructures involving magnetic oxides in which the surface gap is opened to invoke the coupling effect; (iii) the exploration of a novel quantum capacitance approach for the detection of surface states at high temperatures; and (iv) the invention of topological sensors operating at ambient temperature with unprecedented sensitivity and spatial resolution. The transformative concepts include the use of low-dissipation topologically protected surface-states of topological insulators for electronic and spintronic devices such as magnetic transducers, electrically tunable inductors, and quantum computation systems.
Broader Impacts: The proposed project will lead to a new magnetometer technology that exploits bulk properties and surface states of topological insulators. The high sensitivity, high spatial resolution and low-dissipation performance can satisfy the demanding requirements in sensor technology. The successful project is expected to have potential applications in medical research such as brain wave detection and in military surveillance with an enhanced magnetic sensitivity at low fields. The development of this project can potentially improve the competitiveness of the EPSCoR state #8722 (Iowa State) in the area of magnetic sensor devices. Besides the technological impacts, the program has a strong and comprehensive education component. Students will gain invaluable research experience in this highly interdisciplinary area of electrical engineering, physics, and materials science, leading to enhanced training and ability to pursue innovations for the entirety of their careers. The PI will create a multicultural environment by recruiting students from underrepresented groups, particularly female students, through the existing outreach programs "Science Bound" and "Program for Women in Science and Engineering" at Iowa State University. Full tuitions, research assistances and resources will be supplied for their education. The students can have ample opportunities to learn state-of-the-art sensor technology and gain hand-on experience on topological insulators. Such experience will broaden their scientific horizons and thus become invaluable assets to their future careers. The outcomes of the program will be incorporated into a course on sensor technology and disseminated in conferences & through peer-reviewed publications. The PI will also actively participate in the K-12 program at Iowa State and continue to offer mini-lectures on nanotechnology and magnetism. Research frontiers of the topological electromagnetic sensors can be included as interesting demonstrations, aiming to stimulating students' curiosity, creativity, and enthusiasm in science and technology.
