LPEM seminar: Yuki Fuseya, Thursday August 31 at 2:00 pm (Paris time)
ESPCI, Room Charpak, entrance building
ID: 875 1182 8653
Deciphering Topological Signatures: Pronounced Quantum-Size-Effect in Topological Heterojunction Bi/BiSb
By Yuki Fuseya, Department of Engineering Science, University of Electro-Communications, Tokyo, Japan
Bi and BiSb alloys have garnered significant attention as pioneering candidates among three-dimensional topological insulators since the seminal proposal by Fu and Kane . Despite a wealth of research since the initial proposal, the topological properties of these materials remain elusive even after fifteen years. All band structure calculations unanimously designate Bi as topologically trivial [1,2]. In contrast, most ARPES experiments report a nontrivial character for Bi [3,4]. Recent observations of higher-order topology in Bi suggest its inherent triviality .
The discordance between experimental findings and theoretical predictions arises from the fundamental divergence in experimental setup predominantly focused on nano-thin films and nanowires, and theoretical frameworks geared towards infinite size of bulk systems. Consequently, we have undertaken a comprehensive theoretical exploration that aligns more closely with experimental realities, explicitly examining the surface states of Bi nano-thin films and the topological heterojunctions.
The outcomes of our investigation reveal a pivotal insight—Bi exhibits remarkably pronounced quantum size effects owing to its exceptionally long Fermi wavelength (approximately 100nm) [6,7]. These quantum size effects, by their nature, contort the anticipated behaviors, thereby intricately complicating the interpretation of experimental outcomes.