We report the molecular beam epitaxy of Bi1−xSbx thin films (0 ≤ x ≤ 1) on sapphire (0001) substrates using a thin (Bi,Sb)2Te3 buffer layer. The characterization of the films using reflection high energy diffraction, x-ray diffraction, atomic force microscopy, and scanning transmission electron microscopy reveals the epitaxial growth of films of reasonable structural quality. This is further confirmed via x-ray diffraction pole figures that determine the epitaxial registry between the thin film and the substrate. We further investigate the microscopic structure of thin films via Raman spectroscopy, demonstrating how the vibrational modes vary as the composition changes and discussing the implications for the crystal structure. We also characterize the samples using electrical transport measurements.
Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher.
Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?
Some links on this page may take you to non-federal websites. Their policies may differ from this site.
-
-
A scalable platform to synthesize ultrathin heavy metals may enable high efficiency charge-to-spin conversion for next-generation spintronics. Here we report the synthesis of air-stable, epitaxially registered monolayer Pb underneath graphene on SiC (0001) by confinement heteroepitaxy (CHet). Diffraction, spectroscopy, and microscopy reveal CHet-based Pb intercalation predominantly exhibits a mottled hexagonal superstructure due to an ordered network of Frenkel-Kontorova-like domain walls. The system’s air stability enables ex-situ spin torque ferromagnetic resonance (ST-FMR) measurements that demonstrate charge-to-spin conversion in graphene/Pb/ferromagnet heterostructures with a 1.5× increase in the effective field ratio compared to control samples.more » « lessFree, publicly-accessible full text available August 5, 2025
-
We present measurements of thermally generated transverse spin currents in the topological insulator Bi2Se3, thereby completing measurements of interconversions among the full triad of thermal gradients, charge currents, and spin currents. We accomplish this by comparing the spin Nernst magneto-thermopower to the spin Hall magnetoresistance for bilayers of Bi2Se3/CoFeB. We find that Bi2Se3does generate substantial thermally driven spin currents. A lower bound for the ratio of spin current density to thermal gradient is
= (4.9 ± 0.9) × 106 , and a lower bound for the magnitude of the spin Nernst ratio is −0.61 ± 0.11. The spin Nernst ratio for Bi2Se3is the largest among all materials measured to date, two to three times larger compared to previous measurements for the heavy metals Pt and W. Strong thermally generated spin currents in Bi2Se3can be understood via Mott relations to be due to an overall large spin Hall conductivity and its dependence on electron energy. -
The interface between two different materials can show unexpected quantum phenomena. In this study, we used molecular beam epitaxy to synthesize heterostructures formed by stacking together two magnetic materials, a ferromagnetic topological insulator (TI) and an antiferromagnetic iron chalcogenide (FeTe). We observed emergent interface-induced superconductivity in these heterostructures and demonstrated the co-occurrence of superconductivity, ferromagnetism, and topological band structure in the magnetic TI layer—the three essential ingredients of chiral topological superconductivity (TSC). The unusual coexistence of ferromagnetism and superconductivity is accompanied by a high upper critical magnetic field that exceeds the Pauli paramagnetic limit for conventional superconductors at low temperatures. These magnetic TI/FeTe heterostructures with robust superconductivity and atomically sharp interfaces provide an ideal wafer-scale platform for the exploration of chiral TSC and Majorana physics.more » « less