Strain-Engineering of Topological Insulators Using MEMS-Based Carriers

The potential for fine strain tuning to artificially control topological states, induce phase transitions, and modify Dirac cones has been theoretically predicted. It holds great promise for applications in cutting-edge electronic devices, such as straintronics and topological quantum computing. However, methods to controllably and efficiently modulate the crystal lattice while simultaneously observing changes in the electronic structure within a single sample have been rarely reported. Particularly, observing electrical property changes under strain modulation in micron-scale crystals has been limited due to controllability issues. In this presentation, we aim to develop a Si-based MEMS carrier that enables precise strain control to sub-10-micron-long materials, and demonstrate the magneto-electrical transport characterization of HfTe5 nanosheets. Under controlled strain, we observe a strain-driven topological phase transition from a weak topological insulator phase to a strong topological insulator phase. This innovative approach could advance quantum sensing applications as well as the development of quantum electronics and spintronics.