Mott resistive switching initiated by topological defects.

Avalanche resistive switching is the fundamental process that triggers the sudden change of the electrical properties in solid-state devices under the action of intense electric fields. Despite its relevance for information processing, ultrafast electronics, neuromorphic devices, resistive memories and brain-inspired computation, the nature of the local stochastic fluctuations that drive the formation of metallic regions within the insulating state has remained hidden. Here, using operando X-ray nano-imaging, we have captured the origin of resistive switching in a VO-based device under working conditions.

Confinement-Induced Isosymmetric Metal-Insulator Transition in Ultrathin Epitaxial VO Films.

Dimensional confinement has shown to be an effective strategy to tune competing degrees of freedom in complex oxides. Here, we achieved atomic layered growth of trigonal vanadium sesquioxide (VO) by means of oxygen-assisted molecular beam epitaxy. This led to a series of high-quality epitaxial ultrathin VO films down to unit cell thickness, enabling the study of the intrinsic electron correlations upon confinement.

Nanoscale self-organization and metastable non-thermal metallicity in Mott insulators.

Mott transitions in real materials are first order and almost always associated with lattice distortions, both features promoting the emergence of nanotextured phases. This nanoscale self-organization creates spatially inhomogeneous regions, which can host and protect transient non-thermal electronic and lattice states triggered by light excitation. Here, we combine time-resolved X-ray microscopy with a Landau-Ginzburg functional approach for calculating the strain and electronic real-space configurations.

Quantum Conductance in Memristive Devices: Fundamentals, Developments, and Applications.

Quantum effects in novel functional materials and new device concepts represent a potential breakthrough for the development of new information processing technologies based on quantum phenomena. Among the emerging technologies, memristive elements that exhibit resistive switching, which relies on the electrochemical formation/rupture of conductive nanofilaments, exhibit quantum conductance effects at room temperature. Despite the underlying resistive switching mechanism having been exploited for the realization of next-generation memories and neuromorphic computing architectures, the potentialities of quantum effects in memristive devices are still rather unexplored.

Simultaneous growth of three-dimensional carbon nanotubes and ultrathin graphite networks on copper.

A new way to simultaneously grow carbon nanotubes (CNTs) and ultrathin graphite on copper (Cu) foils has been investigated. This one-step growth process yields three-dimensional networks of CNTs on graphitic layers (3D CNTs/G) on Cu foils. Their synthesis conditions and growth mechanism are discussed in detail taking their structural properties into account.

Magnetic orders and origin of exchange bias in Co clusters embedded oxide nanocomposite films.

Magnetic nanoparticles embedded oxide semiconductors are interesting candidates for spintronics in view of combining ferromagnetic (FM) and semiconducting properties. In this work, Co-ZnO and Co-VO nanocomposite thin films are synthesized by Co ion implantation in crystalline thin films. Magnetic orders vary with the implantation fluence in Co-ZnO, where superparamagnetic (SPM) order appears in the low-fluence films (2  ×  10 and 4  ×  10 ions cm) and FM order co-exists with the SPM phase in high-fluence films (1  ×  10 ions cm).

Experimental demonstration of a tunable transverse electric pass polarizer based on hybrid VO/silicon technology.

A tunable transverse electric (TE) pass polarizer is demonstrated based on hybrid vanadium dioxide/silicon (VO/Si) technology. The 20-μm-long TE pass polarizer exploits the phase transition of the active VO material to control the rejection of the unwanted transverse magnetic (TM) polarization. The device features insertion losses below 1 dB at static conditions and insertion losses of 5.

Optical switching in hybrid VO/Si waveguides thermally triggered by lateral microheaters.

The performance of optical devices relying in vanadium dioxide (VO) technology compatible with the silicon platform depends on the polarization of light and VO properties. In this work, optical switching in hybrid VO/Si waveguides thermally triggered by lateral microheaters is achieved with insertion losses below 1 dB and extinction ratios above 20 dB in a broad bandwidth larger than 30 nm. The optical switching response has been optimized for TE and TM polarizations by using a homogeneous and a granular VO layer, respectively, with a small impact on the electrical power consumption.

Type-1.5 superconductivity.

We demonstrate the existence of a novel superconducting state in high quality two-component MgB2 single crystalline superconductors where a unique combination of both type-1 (lambda{1}/xi{1}<1/sqrt[2]) and type-2 (lambda{2}/xi{2}>1/sqrt[2]) superconductor conditions is realized for the two components of the order parameter. This condition leads to a vortex-vortex interaction attractive at long distances and repulsive at short distances, which stabilizes unconventional stripe- and gossamerlike vortex patterns that we have visualized in this type-1.5 superconductor using Bitter decoration and also reproduced in numerical simulations.