Preservation of Topological Surface States in Millimeter-Scale Transferred Membranes

TL;DR

This study demonstrates the successful transfer of millimeter-scale Bi2Se3 topological insulator films while preserving their topological surface states, enabling precise stacking for advanced quantum material engineering.

Contribution

It introduces a method to transfer large-area topological insulator films with preserved surface states, facilitating the fabrication of complex stacked quantum materials.

Findings

Topological surface states are preserved after transfer.

Surface states migrate from the top to inner layers upon transfer.

Established electronic structure of transferred films.

Abstract

Ultrathin topological insulator membranes are building blocks of exotic quantum matter. However, traditional epitaxy of these materials does not facilitate stacking in arbitrary orders, while mechanical exfoliation from bulk crystals is also challenging due to the non-negligible interlayer coupling therein. Here we liberate millimeter-scale films of topological insulator Bi$_2$Se$_3$, grown by molecular beam epitaxy, down to 3 quintuple layers. We characterize the preservation of the topological surface states and quantum well states in transferred Bi$_{2}$Se$_{3}$ films using angle-resolved photoemission spectroscopy. Leveraging the photon-energy-dependent surface sensitivity, the photoemission spectra taken with $6$ eV and $21.2$ eV photons reveal a transfer-induced migration of the topological surface states from the top to the inner layers. By establishing clear electronic structures of the transferred films and unveiling the wavefunction relocation of the topological surface states, our work paves the physics foundation crucial for the future fabrication of artificially stacked topological materials with single-layer precision.