FeTe0.55Se0.45 van der Waals tunneling devices

Abstract

We report on fabrication of devices integrating FeTe0.55Se0.45 with other van-der-Waals materials, measuring transport properties as well as tunneling spectra at variable magnetic fields and temperatures down to 35 mK. Transport measurements are reliable and repeatable, revealing temperature and magnetic field dependence in agreement with prior results, confirming that fabrication processing does not alter bulk properties. However, cross-section scanning transmission microscopy reveals oxidation of the surface, which may explain a lower yield of tunneling device fabrication. We nonetheless observe hard-gap planar tunneling into FeTe0.55Se0.45 through a MoS2 barrier. Notably, a minimal hard gap of 0.5 meV persists up to a magnetic field of 9 T in the ab plane and 3 T out of plane. This may be the result of very small junction dimensions, or a quantum-limit minimal energy spacing between vortex bound states. We also observed defect assisted tunneling, exhibiting bias-symmetric resonant states which may arise due to resonant Andreev processes.

Magnetic surface reconstruction in the van der Waals antiferromagnet Fe1+xTe

“…The electronic and magnetic properties of Fe 1+x Te 1−y Q y can be tuned via two variables-the parameter x determines the amount of interstitial iron located between the weakly bonded FeTe layers and disordered throughout the crystal, and y is the amount of anion substitution and provides a chemical route toward superconductivity. It should be noted that while the interstitial iron is disordered introducing magnetic clusters [25], the electronic properties have been found to be homogeneous [26,27], and they were recently discussed in the context of device fabrication [28]. The sensitivity of the properties to stoichiometry is also reflected in Fe 1+δ Se [29].…”

Spin Proximity Effects in Graphene/Topological Insulator Heterostructures

“…26 Additionally, the fact that electronic states in Gr/TMDC sys-tems are spin-polarized primarily along the outof-plane direction 27 results in large spin lifetime anisotropy between in-plane and out-ofplane spin-polarized electrons, which is however weakly energy dependent and therefore not tunable. [28][29][30] Recently, a lot of attention has been paid to heterostructures of graphene and topological insulators (TIs), with reports of anomalous magnetotransport, giant Edelstein effect, and gate-tunable tunneling resistance, [31][32][33][34][35] as well as the possible existence of a quantum spin Hall phase. 36,37 On the more applied side, the fabrication of broadband photodetectors based on Gr/TI heterostructures has been realized, 38 as well as the injection of spin-polarized current from an ultrathin Bi 2 Te 2 Se nanoplatelet into graphene.…”

A Cleanroom in a Glovebox

“…We note that there are a variety of options for fabrication which completely eliminate water from the process, including shadow (or stencil) mask techniques and transferring flakes onto pre-written contacts. 26,27 The lack of contamination along with the alignment abilities of the mask-less system was crucial in creating high-quality devices and periodic structures (see Fig. 4d and 4e).…”