Giant Magnetic Band Gap in the Rashba-Split Surface State of Vanadium-Doped BiTeI: A Combined Photoemission and Ab Initio Study

Abstract

One of the most promising platforms for spintronics and topological quantum computation is the two-dimensional electron gas (2DEG) with strong spin-orbit interaction and out-of-plane ferromagnetism. In proximity to an s-wave superconductor, such 2DEG may be driven into a topologically non-trivial superconducting phase, predicted to support zero-energy Majorana fermion modes. Using angle-resolved photoemission spectroscopy and ab initio calculations, we study the 2DEG at the surface of the vanadium-doped polar semiconductor with a giant Rashba-type splitting, BiTeI. We show that the vanadium-induced magnetization in the 2DEG breaks time-reversal symmetry, lifting Kramers degeneracy of the Rashba-split surface state at the Brillouin zone center via formation of a huge gap of about 90 meV. As a result, the constant energy contour inside the gap consists of only one circle with spin-momentum locking. These findings reveal a great potential of the magnetically-doped semiconductors with a giant Rashba-type splitting for realization of novel states of matter.

Dirac gap opening and Dirac-fermion-mediated magnetic coupling in antiferromagnetic Gd-doped topological insulators and their manipulation by synchrotron radiation

“…The AFM coupling was also observed for the layered magnetically-doped BiTeI 44 , 45 , for layered RE-Rh 2 Si 2 systems (where RE is Gd, Ho) 41 and for recently discovered magnetically-ordered stoichiometric AFM TI MnBi 2 Te 4 32 , 33 , 46 , where the magnetic coupling is provided by an AFM coupling between the magnetic Mn atoms in the neighbor quintuple layers with alternating magnetic moments 47 . Inside each magnetic layer the magnetic coupling is ferromagnetic.…”

Non-monotonic variation of the Kramers point band gap with increasing magnetic doping in BiTeI

“…In earlier works, devoted to experimental and theoretical study of V-doped BiTeI 9 , 28 , it was shown that the KP gap reaches the value of ~ 90 meV with the V concentration of 2%. Remarkably, the ab-initio calculations reveal KP gap no greater than 34 meV in this case 9 .…”

“…In earlier works, devoted to experimental and theoretical study of V-doped BiTeI 9 , 28 , it was shown that the KP gap reaches the value of ~ 90 meV with the V concentration of 2%. Remarkably, the ab-initio calculations reveal KP gap no greater than 34 meV in this case 9 . This discrepancy could be related to unaccounted Bi-vacancies in the vicinity of V impurities, which can affect the magnetic moments of the nearest Te atoms and increase the gap value.…”

“…The magnetization has to be directed perpendicular to the sample surface to open the gap in all . The spin structure of the state becomes “hedgehog”-shape in the vicinity of the KP and the electronic structure can be tuned to have one circular Fermi contour 9 . Similar spin degeneracy lifting can be observed in magnetic topological insulators for the topological surface state 10 – 15 or Rashba-like state 16 .…”

Non-monotonic variation of the Kramers point band gap with increasing magnetic doping in BiTeI

“…The magnetization has to be directed perpendicular to the sample surface to open the gap in all k . The spin structure of the state becomes "hedgehog"-shape in the vicinity of the KP and the electronic structure can be tuned to have one circular Fermi contour 9 . Similar spin degeneracy lifting can be observed in magnetic topological insulators for the topological surface state [10][11][12][13][14][15] or Rashba-like state 16 .…”