A cascading nonlinear magneto-optical effect in topological insulators

Richarj Mondal, Yuta Saito, Yuki Aihara, Paul Fons, Alexander V. Kolobov, Junji Tominaga, Shuichi Murakami, Muneaki Hase

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


Topological insulators (TIs) are characterized by possessing metallic (gapless) surface states and a finite band-gap state in the bulk. As the thickness of a TI layer decreases down to a few nanometers, hybridization between the top and bottom surfaces takes place due to quantum tunneling, consequently at a critical thickness a crossover from a 3D-TI to a 2D insulator occurs. Although such a crossover is generally accessible by scanning tunneling microscopy, or by angle-resolved photoemission spectroscopy, such measurements require clean surfaces. Here, we demonstrate that a cascading nonlinear magneto-optical effect induced via strong spin-orbit coupling can examine such crossovers. The helicity dependence of the time-resolved Kerr rotation exhibits a robust change in periodicity at a critical thickness, from which it is possible to predict the formation of a Dirac cone in a film several quintuple layers thick. This method enables prediction of a Dirac cone using a fundamental nonlinear optical effect that can be applied to a wide range of TIs and related 2D materials.

Original languageEnglish
Article number3908
JournalScientific reports
Issue number1
Publication statusPublished - 2018 Dec 1
Externally publishedYes

ASJC Scopus subject areas

  • General


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