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Giant magnetoresistance and perfect spin filter in silicene, germanene, and stanene
Stephan Rachel, Motohiko Ezawa
Silicene, germanene and stanene are two-dimensional topological insulators exhibiting helical edge states. We investigate global and local manipulations at the edges by exposing th…
Symmetry Protected Topological Charge in Symmetry Broken Phase: Spin-Chern, Spin-Valley-Chern and Mirror-Chern Numbers
Motohiko Ezawa
The Chern number is a genuine topological number. On the other hand, a symmetry protected topological (SPT) charge is a topological number only when a symmetry exists. We propose a…
Topological Kirchhoff Law and Bulk-Edge Correspondence for Valley-Chern and Spin-Valley-Chern Numbers
Motohiko Ezawa
The valley-Chern and spin-valley-Chern numbers are the key concepts in valleytronics. They are topological numbers in the Dirac theory but not in the tight-binding model. We analyz…
Edge States in Silicene Nanodisks
Ko Kikutake, Motohiko Ezawa, Naoto Nagaosa
Silicene is a honeycomb-structure silicon atoms, which shares many intriguing properties with graphene. Silicene is expected to be a quantum spin-Hall insulator due to its spin-orb…
Topological Phase Transition without Gap Closing
Motohiko Ezawa, Yukio Tanaka, Naoto Nagaosa
Topological phase transition is accompanied with a change of topological numbers. It has been believed that the gap closing and the breakdown of the adiabaticity at the transition…
Quantum Hall Effects with High Spin-Chern Numbers in Buckled Honeycomb Structure with Magnetic Order
Motohiko Ezawa
As a topological insulator, the quantum Hall (QH) effect is indexed by the Chern and spin-Chern numbers and . We have only $\mathcal{C}_{\t…