The impending end of Moore’s Law has prompted a search for a new computing technology with vastly lower energy consumed per operation than silicon CMOS. The recent discovery of topological phases of matter offers a possible solution: a “topological transistor” in which an electric field tunes a material from a conventional insulator “off” state to a topological insulator “on” state, in which topologically protected edge modes carry dissipationless current. Due to the combined effects of Rashba spin-orbit interaction and electric field control of the bandgap, the topological transistor may switch at lower voltage, overcoming “Boltzmann’s tyranny”.
I will discuss our work on atomically thin films of Na3Bi as a platform for a topological transistor. We study thin films of Na3Bi grown in ultra-high vacuum by molecular beam epitaxy, characterized with electronic transport, scanning tunneling microscopy (STM), and angle-resolved photoemission spectroscopy (for a review, see Ref. ). When thinned to a few atomic layers Na3Bi is a large gap (>300 meV) 2D topological insulator with topologically protected edge modes observable in STM. Electric field applied perpendicular to the Na3Bi film closes the bandgap completely and reopens it as a conventional insulator. Electrical transport measurements demonstrate that the current is carried by helical topological edge modes over millimeter-scale distances. The large bandgap of 2D Na3Bi, significantly greater than room temperature, and its compatibility with silicon, make it a promising platform for topological transistors.
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