Magnetic Gap of Fe-Doped BiSbTe₂Se Bulk Single Crystals Detected by Tunneling Spectroscopy and Gate-Controlled Transports

Abstract

Topological insulators with broken time-reversal symmetry and the Fermi level within the magnetic gap at the Dirac cone provides exotic topological magneto-electronic phenomena. Here, we introduce an improved magnetically doped topological insulator, Fedoped BiSbTe 2 Se (Fe-BSTS) bulk single crystal, with an ideal Fermi level. Scanning tunneling microscopy and spectroscopy (STM/STS) measurements revealed that the surface state possesses a Dirac cone with the Dirac point just below the Fermi level by 12 meV. The normalized dI/dV spectra suggest a gap opening with Δ mag ∼55 meV, resulting in the Fermi level within the opened gap. Ionic-liquid gated-transport measurements also support the Dirac point just below the Fermi level and the presence of the magnetic gap. The chemical potential of the surface state can be fully tuned by ionic-liquid gating, and thus the Fe-doped BSTS provides an ideal platform to investigate exotic quantum topological phenomena.

Superconducting Long-Range Proximity Effect through the Atomically Flat Interface of a Bi2Te3 Topological Insulator

“…In this respect, the interface between superconductors (S) and a topological insulator (TI) is expected to induce by proximity peculiar properties such as unconventional superconductivity. , Topologically protected surface states − are attractive not only from the fundamental point of view, such as the realization of Majorana modes, − but also for spintronics applications, in view of their robustness and the forbidden backscattering. − The couple Pb/Bi 2 Te 3 is a good candidate for such a study. Bi 2 Te 3 is a three-dimensional (3D) TI showing high electron mobility of topological (surface) states and a relatively low contribution of trivial (bulk) electronic states to the total electron transport .…”

Lateral Josephson Junctions as Sensors for Magnetic Microscopy at Nanoscale

“…The lateral geometry of LJJ makes them suitable for studying Josephson phenomena at the nanoscale by scanning probe microscopes (SPM) such as tunneling microscopy and spectroscopy, ,− scanning SQUID, − or magnetic force microscopy (MFM). ,− The latter technique is particularly promising owing to its simplicity and its capacity to reveal the spatial distribution of the magnetic field over LJJ. Yet quantitative MFM measurements are rare, due to difficulties related to the calibration of magnetic MFM probes.…”

Revealing intrinsic superconductivity of the Nb/BiSbTe$_2$Se interface

“…As a result, the low concentration of the bulk carriers leads to the surface dominated transport at low temperature. 17 Thin flakes of Fe-BSTS were mechanically exfoliated from the bulk material, transferred to the Si/SiO 2 substrate, and then SQUID on top of the flake was fabricated using a standard technological process (See Section 1 of the Supplemental Materials for details). Schematic drawing of the final device is shown in the inset of the Figure 1c.…”