Axially lattice-matched wurtzite/rock-salt GaAs/PbSnTe nanowires.

We investigate the full and half-shells of PbSnTe topological crystalline insulator deposited by molecular beam epitaxy on the sidewalls of wurtzite GaAs nanowires (NWs). Due to the distinct orientation of the IV-VI shell with respect to the III-V core the lattice mismatch between both materials along the nanowire axis is less than 4%. The PbSnTe solid solution is chosen due to the topological crystalline insulator properties above some critical concentrations of Sn (x ≥ 0.

Defect-free SnTe topological crystalline insulator nanowires grown by molecular beam epitaxy on graphene.

SnTe topological crystalline insulator nanowires have been grown by molecular beam epitaxy on graphene/SiC substrates. The nanowires have a cubic rock-salt structure, they grow along the [001] crystallographic direction and have four sidewalls consisting of {100} crystal planes known to host metallic surface states with a Dirac dispersion. Thorough high resolution transmission electron microscopy investigations show that the nanowires grow on graphene in the van der Waals epitaxy mode induced when the catalyzing Au nanoparticles mix with Sn delivered from a SnTe flux, providing a liquid Au-Sn alloy.

Fragility of the Dirac Cone Splitting in Topological Crystalline Insulator Heterostructures.

The "double Dirac cone" 2D topological interface states found on the (001) faces of topological crystalline insulators such as PbSnSe feature degeneracies located away from time reversal invariant momenta and are a manifestation of both mirror symmetry protection and valley interactions. Similar shifted degeneracies in 1D interface states have been highlighted as a potential basis for a topological transistor, but realizing such a device will require a detailed understanding of the intervalley physics involved. In addition, the operation of this or similar devices outside of ultrahigh vacuum will require encapsulation, and the consequences of this for the topological interface state must be understood.

Robust spin-polarized midgap states at step edges of topological crystalline insulators.

Topological crystalline insulators are materials in which the crystalline symmetry leads to topologically protected surface states with a chiral spin texture, rendering them potential candidates for spintronics applications. Using scanning tunneling spectroscopy, we uncover the existence of one-dimensional (1D) midgap states at odd-atomic surface step edges of the three-dimensional topological crystalline insulator (Pb,Sn)Se. A minimal toy model and realistic tight-binding calculations identify them as spin-polarized flat bands connecting two Dirac points.

Direct observation and temperature control of the surface Dirac gap in a topological crystalline insulator.

Since the advent of topological insulators hosting Dirac surface states, efforts have been made to gap these states in a controllable way. A new route to accomplish this was opened up by the discovery of topological crystalline insulators where the topological states are protected by crystal symmetries and thus prone to gap formation by structural changes of the lattice. Here we show a temperature-driven gap opening in Dirac surface states within the topological crystalline insulator phase in (Pb,Sn)Se.

Novel ZnO/MgO/Fe2O3 composite optomagnetic nanoparticles.

A facile sol-gel synthesis of novel ZnO/MgO/Fe2O3 nanoparticles (NPs) is reported and their performance is compared to that of ZnO/MgO. Powder x-ray diffraction (XRD) patterns reveal the crystal structure of the prepared samples. The average particle size of the sample was found to be 4.

The mechanism of Bi nanowire growth from Bi/Co immiscible composite thin films.

Single crystalline Bi nanowires were grown by extrusion from Bi/Co thin films. The films were obtained by thermal evaporation in high vacuum. The average diameter, length and density of obtained nanowires were 100 nm, 30 microm and 6.

Topological crystalline insulator states in Pb(1-x)Sn(x)Se.

Topological insulators are a class of quantum materials in which time-reversal symmetry, relativistic effects and an inverted band structure result in the occurrence of electronic metallic states on the surfaces of insulating bulk crystals. These helical states exhibit a Dirac-like energy dispersion across the bulk bandgap, and they are topologically protected. Recent theoretical results have suggested the existence of topological crystalline insulators (TCIs), a class of topological insulators in which crystalline symmetry replaces the role of time-reversal symmetry in ensuring topological protection.