Kinetic Monte Carlo simulations on electroforming in nanomanipulated conductive bridge random access memory devices.

Conductive bridge random access memory (CBRAM) devices exhibit great potential as the next-generation nonvolatile memory devices. However, they suffer from two major disadvantages, namely relatively high power consumption and large cycle-to-cycle and device-to-device variations, which hinder their more extensive commercialization. To learn how to enhance their device performance, kinetic Monte Carlo (KMC) simulations were employed to illustrate the variation of electroforming processes in nanomanipulated CBRAM devices by introducing an ion-blocking layer with scalable nanopores and tuning the microstructures of dielectric layers.

Computational Study on Interlocked-Ferroelectricity-Contributed High-Performance Memristors Based on Two-Dimensional van der Waals Ferroelectric Semiconductors.

In order to realize the prevailing artificial intelligence technology, memristor-implemented in-memory or neuromorphic computing is highly expected to break the bottleneck of von Neumann computers. Although high-performance memristors have been vigorously developed in labs or in industry, systematic computational investigations on memristors are seldom. Hence, it is urgent to provide theoretical or computational support for the exploration of memristor operating mechanisms or the screening of memristor materials.

A Superconducting Micro-Magnetometer for Quantum Vortex in Superconducting Nanoflakes.

Superconducting quantum interferometer device (SQUID) plays a key role in understanding electromagnetic properties and emergent phenomena in quantum materials. The technological appeal of SQUID is that its detection accuracy for the electromagnetic signal can precisely reach the quantum level of a single magnetic flux. However, conventional SQUID techniques normally can only be applied to a bulky sample and do not have the capability to probe the magnetic properties of micro-scale samples with small magnetic signals.

Direct Growth of van der Waals Tin Diiodide Monolayers.

Two-dimensional (2D) van der Waals (vdW) materials have garnered considerable attention for their unique properties and potentials in a wide range of fields, which include nano-electronics/optoelectronics, solar energy, and catalysis. Meanwhile, challenges in the approaches toward achieving high-performance devices still inspire the search for new 2D vdW materials with precious properties. In this study, via molecular beam epitaxy, for the first time, the vdW SnI monolayer is successfully fabricated with a new structure.

Non-hydrostatic pressure-dependent structural and transport properties of BiCuSeO and BiCuSO single crystals.

High-pressure experiments usually expect a hydrostatic condition, in which the physical properties of materials can be easily understood by theoretical simulations. Unfortunately, non-hydrostatic effect is inevitable in experiments due to the solidification of the pressure transmitting media under high pressure. Resultantly, non-hydrostaticity affects the accuracy of the experimental data and sometimes even leads to false phenomena.

Kinetics-Limited Two-Step Growth of van der Waals Puckered Honeycomb Sb Monolayer.

Puckered honeycomb Sb monolayer, the structural analog of black phosphorene, has been recently successfully grown by means of molecular beam epitaxy. However, little is known to date about the growth mechanism for such a puckered honeycomb monolayer. In this study, by using scanning tunneling microscopy in combination with first-principles density functional theory calculations, we unveil that the puckered honeycomb Sb monolayer takes a kinetics-limited two-step growth mode.

Tuning the Electronic Structure of an α-Antimonene Monolayer through Interface Engineering.

The interfacial charge transfer from the substrate may influence the electronic structure of the epitaxial van der Waals (vdW) monolayers and, thus, their further technological applications. For instance, the freestanding Sb monolayer in the puckered honeycomb phase (α-antimonene), the structural analogue of black phosphorene, was predicted to be a semiconductor, but the epitaxial one behaves as a gapless semimetal when grown on the -WTe substrate. Here, we demonstrate that interface engineering can be applied to tune the interfacial charge transfer and, thus, the electron band of the epitaxial monolayer.

Anomalous transport and magnetic properties induced by slight Cu valence alternation in layered oxytelluride BiCuTeO.

In this paper, we report on the transport and magnetic properties of layered oxytelluride BiCuTeO polycrystals with slight mixed valence of Cu. The temperature-dependent electrical resistivity reveals degenerate semiconductor behavior (similar to metals). Under the action of an external magnetic field, the BiCuTeO polycrystal sample exhibits unsaturated magnetic resistance (MR) of about 8% at 2 K and 9 Tesla.

Electrical scattering mechanism evolution in un-doped and halogen-doped BiOSe single crystals.

Recently the layered oxide semiconductor BiOSe was hotly explored for its ultrahigh mobility and ultrafast photo-response whose physical origins need to be further explored or elucidated. Here, we have grown halogen (Cl, Br, I) doped and un-doped BiOSe single crystals by a melt-solidification method. Comparative electrical transport characterizations and detailed data-analysis substantiate that the electron-electron scattering is the major source of resistivity in un-doped BiOSe crystals; however, in halogen-doped BiOSe crystals, electron-electron scattering is only effective at low temperature (<60 K) and subsequently electron-phonon-interaction scattering is dominated to resistivity.

Synthesis, structure, and electronic properties of the LiRbGdTeO single crystal.

Materials with spin dimers have attracted much attention in the last several decades because they could provide a playground to embody simple quantum spin models. For example, the Bose-Einstein condensation of magnons has been observed in TlCuCl with anti-ferromagnetic CuCl dimers. In this work, we have synthesized a new kind of single-crystal LiRbGdTeO with GdO dimers.

Infrared and Raman spectra of BiOX and BiOX (X = S, Se, and Te) studied from first principles calculations.

The bismuth oxychalcogenide compounds contain many different kinds of materials, such as BiOX and BiOX (X = S, Se, and Te). These materials have different but similar layered crystal structures and exhibit various interesting physical properties. Here, we have theoretically investigated their Raman and infrared spectra by first principles calculations based on density functional theory.

Van der Waals Heteroepitaxial Growth of Monolayer Sb in a Puckered Honeycomb Structure.

Atomically thin 2D crystals have gained tremendous attention owing to their potential impact on future electronics technologies, as well as the exotic phenomena emerging in these materials. Monolayers of α-phase Sb (α-antimonene), which shares the same puckered structure as black phosphorous, are predicted to be stable with precious properties. However, the experimental realization still remains challenging.

Superconductivity in Potassium-Intercalated T -WTe.

To realize a topological superconductor is one of the most attracting topics because of its great potential in quantum computation. In this study, we successfully intercalate potassium (K) into the van der Waals gap of type II Weyl semimetal WTe and discover the superconducting state in K WTe through both electrical transport and scanning tunneling spectroscopy measurements. The superconductivity exhibits an evident anisotropic behavior.

Preparation, Structure Evolution, and Metal-Insulator Transition of Na RhO Crystals (0.25 ≤ x ≤ 1).

The triangular lattice Na RhO contains a 4d Rh element with large spin-orbit coupling, and the electron-electron correlation effect is expected to have some novel physical properties. Here we report NaRhO crystal growth by NaCO vapor growth and a series of Na RhO (0.25 ≤ x ≤ 1) crystals prepared using the chemical desodiation method.

Nematic superconducting state in iron pnictide superconductors.

Nematic order often breaks the tetragonal symmetry of iron-based superconductors. It arises from regular structural transition or electronic instability in the normal phase. Here, we report the observation of a nematic superconducting state, by measuring the angular dependence of the in-plane and out-of-plane magnetoresistivity of BaKFeAs single crystals.

Composition and temperature-dependent phase transition in miscible MoWTe single crystals.

Transition metal dichalcogenides (TMDs) WTe and MoTe with orthorhombic Td phase, being potential candidates as type-II Weyl semimetals, are attracted much attention recently. Here we synthesized a series of miscible MoWTe single crystals by bromine vapor transport method. Composition-dependent X-ray diffraction and Raman spectroscopy, as well as composition and temperature-dependent resistivity prove that the tunable crystal structure (from hexagonal (2H), monoclinic (β) to orthorhombic (Td) phase) can be realized by increasing W content in MoWTe.

Transcutaneous electrical acupoint stimulation as an adjunct therapy for obsessive-compulsive disorder: A randomized controlled study.

Background: Transcutaneous electrical acupoint stimulation (TEAS) is thought to have potential to treat obsessive-compulsive disorder (OCD).

Objective: The purpose of this study was to determine whether adding TEAS to cognitive behavioral therapy (CBT) and clomipramine would improve the efficacy of these conventional treatments in OCD.

Methods: In this randomized controlled trial, 360 OCD patients were assigned to receive TEAS combined with CBT plus clomipramine (Group A, n = 120), TEAS combined with CBT plus placebo (Group B, n = 120), and simulated (placebo) TEAS combined with CBT plus clomipramine (Group C, n = 120) for 12 weeks.

Dramatically decreased magnetoresistance in non-stoichiometric WTe2 crystals.

Recently, the layered semimetal WTe2 has attracted renewed interest owing to the observation of a non-saturating and giant positive magnetoresistance (~10(5)%), which can be useful for magnetic memory and spintronic devices. However, the underlying mechanisms of the giant magnetoresistance are still under hot debate. Herein, we grew the stoichiometric and non-stoichiometric WTe2 crystals to test the robustness of giant magnetoresistance.

Experimental Observation of Topological Edge States at the Surface Step Edge of the Topological Insulator ZrTe_{5}.

We report an atomic-scale characterization of ZrTe_{5} by using scanning tunneling microscopy. We observe a bulk band gap of ∼80  meV with topological edge states at the step edge and, thus, demonstrate that ZrTe_{5} is a two-dimensional topological insulator. We also find that an applied magnetic field induces an energetic splitting of the topological edge states, which can be attributed to a strong link between the topological edge states and bulk topology.