Observation of quantum-tunnelling-modulated spin texture in ultrathin topological insulator Bi2Se3 films

Madhab Neupane, Anthony Richardella, Jaime Sánchez-Barriga, Su Yang Xu, Nasser Alidoust, Ilya Belopolski, Chang Liu, Guang Bian, Duming Zhang, Dmitry Marchenko, Andrei Varykhalov, Oliver Rader, Mats Leandersson, Thiagarajan Balasubramanian, Tay Rong Chang, Horng Tay Jeng, Susmita Basak, Hsin Lin, Arun Bansil, Nitin SamarthM. Zahid Hasan

Research output: Contribution to journalArticlepeer-review

114 Scopus citations


Understanding the spin-texture behaviour of boundary modes in ultrathin topological insulator films is critically essential for the design and fabrication of functional nanodevices. Here, by using spin-resolved photoemission spectroscopy with p-polarized light in topological insulator Bi2Se3 thin films, we report tunnelling-dependent evolution of spin configuration in topological insulator thin films across the metal-to-insulator transition. We report a systematic binding energy- and wavevector-dependent spin polarization for the topological surface electrons in the ultrathin gapped-Dirac-cone limit. The polarization decreases significantly with enhanced tunnelling realized systematically in thin insulating films, whereas magnitude of the polarization saturates to the bulk limit faster at larger wavevectors in thicker metallic films. We present a theoretical model that captures this delicate relationship between quantum tunnelling and Fermi surface spin polarization. Our high-resolution spin-based spectroscopic results suggest that the polarization current can be tuned to zero in thin insulating films forming the basis for a future spin-switch nanodevice.

Original languageEnglish (US)
Article number3841
JournalNature communications
StatePublished - May 12 2014

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • General Biochemistry, Genetics and Molecular Biology
  • General Physics and Astronomy


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