Observation of Two-Dimensional Bulk Electronic States in a Superconducting Topological Insulator Heterostructure Cux(PbSe)5(Bi2Se3)6: Implications for Unconventional Superconductivity

TL;DR

This study uses ARPES to reveal two-dimensional bulk electronic states in a superconducting topological insulator heterostructure, suggesting potential for unconventional pairing and Majorana states.

Contribution

First direct observation of 2D bulk electronic states in a superconducting topological heterostructure using ARPES, indicating possible unconventional superconductivity mechanisms.

Findings

Bulk conduction band shifts with Cu doping

Bulk band forms a cylindrical electronlike Fermi surface

Two-dimensional bulk states imply odd-parity or d-wave pairing

Abstract

We have performed angle-resolved photoemission spectroscopy (ARPES) on Cux(PbSe)5(Bi2Se3)6 (CPSBS; x = 1.47), a superconductor derived from a topological insulator heterostructure, to elucidate the electronic states relevant to the occurrence of possible unconventional superconductivity. Upon Cu intercalation into the parent compound (PbSe)5(Bi2Se3)6, we observed a distinct energy shift of the bulk conduction band due to electron doping. Photon-energy dependent ARPES measurements of CPSBS revealed that the observed bulk band forms a cylindrical electronlike Fermi surface at the Brillouin-zone center. The two-dimensional nature of the bulk electronic states suggests the occurrence of odd-parity Eu pairing or even-parity d-wave pairing, both of which may provide a platform of Majorana bound states in the superconducting state.