Reducing Disorder in PbTe Nanowires for Majorana Research.

Material challenges are the key issue in Majorana research, where surface disorder constrains device performance. Here, we tackle this challenge by embedding PbTe nanowires within a lattice-constant-matched crystal. The wire edges are shaped by self-organized growth instead of lithography, resulting in nearly atomically flat facets along both cross-sectional and longitudinal directions.

Gate-tunable subband degeneracy in semiconductor nanowires.

Degeneracy and symmetry have a profound relation in quantum systems. Here, we report gate-tunable subband degeneracy in PbTe nanowires with a nearly symmetric cross-sectional shape. The degeneracy is revealed in electron transport by the absence of a quantized plateau.

Electronic inhomogeneity and phase fluctuation in one-unit-cell FeSe films.

One-unit-cell FeSe films on SrTiO substrates are of great interest owing to significantly enlarged pairing gaps characterized by two coherence peaks at ±10 meV and ±20 meV. In-situ transport measurement is desired to reveal novel properties. Here, we performed in-situ microscale electrical transport and combined scanning tunneling microscopy measurements on continuous one-unit-cell FeSe films with twin boundaries.

Selective-Area-Grown PbTe-Pb Planar Josephson Junctions for Quantum Devices.

Planar Josephson junctions are predicted to host Majorana zero modes. The material platforms in previous studies are two-dimensional electron gases (InAs, InSb, InAsSb, and HgTe) coupled to a superconductor such as Al or Nb. Here, we introduce a new material platform for planar JJs, the PbTe-Pb hybrid.

Ballistic PbTe Nanowire Devices.

Disorder is the primary obstacle in the current Majorana nanowire experiments. Reducing disorder or achieving ballistic transport is thus of paramount importance. In clean and ballistic nanowire devices, quantized conductance is expected, with plateau quality serving as a benchmark for disorder assessment.

Competing Energy Scales in Topological Superconducting Heterostructures.

Artificially engineered topological superconductivity has emerged as a viable route to create Majorana modes. In this context, proximity-induced superconductivity in materials with a sizable spin-orbit coupling has been intensively investigated in recent years. Although there is convincing evidence that superconductivity may indeed be induced, it has been difficult to elucidate its topological nature.

Type-II Ising pairing in few-layer stanene.

Spin-orbit coupling has proven indispensable in the realization of topological materials and, more recently, Ising pairing in two-dimensional superconductors. This pairing mechanism relies on inversion symmetry-breaking and sustains anomalously large in-plane polarizing magnetic fields whose upper limit is predicted to diverge at low temperatures. Here, we show that the recently discovered superconductor few-layer stanene, epitaxially strained gray tin (α-Sn), exhibits a distinct type of Ising pairing between carriers residing in bands with different orbital indices near the Γ-point.

Dimensional Crossover and Topological Nature of the Thin Films of a Three-Dimensional Topological Insulator by Band Gap Engineering.

Identification and control of topological phases in topological thin films offer great opportunities for fundamental research and the fabrication of topology-based devices. Here, combining molecular beam epitaxy, angle-resolved photoemission spectroscopy, and calculations, we investigate the electronic structure evolution in (BiIn)Se films (0 ≤ ≤ 1) with thickness from 2 to 13 quintuple layers. By employing both thickness and In substitution as two independent "knobs" to control the gap change, we identify the evolution between several topological phases, i.

Dimensional Crossover-Induced Topological Hall Effect in a Magnetic Topological Insulator.

We report transport studies of Mn-doped Bi_{2}Te_{3} topological insulator (TI) films with an accurately controlled thickness grown by molecular beam epitaxy. We find that films thicker than five quintuple layers (QLs) exhibit the usual anomalous Hall effect for magnetic TIs. When the thickness is reduced to four QLs, however, characteristic features associated with the topological Hall effect (THE) emerge.

Correction: Broadband ultrafast photovoltaic detectors based on large-scale topological insulator SbTe/STO heterostructures.

Correction for 'Broadband ultrafast photovoltaic detectors based on large-scale topological insulator SbTe/STO heterostructures' by Honghui Sun, et al., Nanoscale, 2017, 9, 9325-9332.

Thickness-dependent carrier and phonon dynamics of topological insulator BiTe thin films.

As a new quantum state of matter, topological insulators offer a new platform for exploring new physics, giving rise to fascinating new phenomena and new devices. Lots of novel physical properties of topological insulators have been studied extensively and are attributed to the unique electron-phonon interactions at the surface. Although electron behavior in topological insulators has been studied in detail, electron-phonon interactions at the surface of topological insulators are less understood.

Broadband ultrafast photovoltaic detectors based on large-scale topological insulator SbTe/STO heterostructures.

Topological insulators (TIs) are new states of quantum matter in which the spin-momentum-locked surface states reside in the bulk insulating gap and have triggered extensive investigations on fundamental properties and potential applications. Herein, we report scalable, broadband photovoltaic detectors based on the topological insulator SbTe/strontium titanate (STO) heterostructure. Large-scale (2 mm × 5 mm), high crystalline quality p-type SbTe films were fabricated on an n-type STO substrate by the molecular beam epitaxy (MBE) method.

Experimental observation of Dirac-like surface states and topological phase transition in Pb(1-x)Sn(x)Te(111) films.

The surface of a topological crystalline insulator (TCI) carries an even number of Dirac cones protected by crystalline symmetry. We epitaxially grew high-quality Pb(1-x)Sn(x)Te(111) films and investigated the TCI phase by in situ angle-resolved photoemission spectroscopy. Pb(1-x)Sn(x)Te(111) films undergo a topological phase transition from a trivial insulator to TCI via increasing the Sn/Pb ratio, accompanied by a crossover from n-type to p-type doping.