Unconventional magnetoresistance and resistivity scaling in amorphous CoSi thin films.

The resistivity scaling of Cu electrical interconnects represents a critical challenge in Si CMOS technology. As interconnect dimensions reach below 10 nm, Cu resistivity increases significantly due to surface scattering. Topological materials have been considered for application in ultra-scaled interconnects (below 5 nm), due to their topologically protected surface states that have reduced electron scattering.

Intrinsic negative magnetoresistance from the chiral anomaly of multifold fermions.

The chiral anomaly - a hallmark of chiral spin-1/2 Weyl fermions - is an imbalance between left- and right-moving particles that underpins phenomena such as particle decay and negative longitudinal magnetoresistance in Weyl semimetals. The discovery that chiral crystals can host higher-spin generalizations of Weyl quasiparticles without high-energy counterparts, known as multifold fermions, raises the fundamental question of whether the chiral anomaly is a more general phenomenon. Answering this question requires materials with chiral quasiparticles within a sizable energy window around the Fermi level that are unaffected by extrinsic effects such as current jetting.

Highly reproducible and CMOS-compatible VO-based oscillators for brain-inspired computing.

With remarkable electrical and optical switching properties induced at low power and near room temperature (68 °C), vanadium dioxide (VO) has sparked rising interest in unconventional computing among the phase-change materials research community. The scalability and the potential to compute beyond the von Neumann model make VO especially appealing for implementation in oscillating neural networks for artificial intelligence applications, to solve constraint satisfaction problems, and for pattern recognition. Its integration into large networks of oscillators on a Silicon platform still poses challenges associated with the stabilization in the correct oxidation state and the ability to fabricate a structure with predictable electrical behavior showing very low variability.

Magnetoresistive-coupled transistor using the Weyl semimetal NbP.

Semiconductor transistors operate by modulating the charge carrier concentration of a channel material through an electric field coupled by a capacitor. This mechanism is constrained by the fundamental transport physics and material properties of such devices-attenuation of the electric field, and limited mobility and charge carrier density in semiconductor channels. In this work, we demonstrate a new type of transistor that operates through a different mechanism.

Full thermoelectric characterization of a single molecule.

Molecules are predicted to be chemically tunable towards high thermoelectric efficiencies and they could outperform existing materials in the field of energy conversion. However, their capabilities at the more technologically relevant temperature of 300 K are yet to be demonstrated. A possible reason could be the lack of a comprehensive technique able to measure the thermal and (thermo)electrical properties, including the role of phonon conduction.

Disorder-Induced Magnetotransport Anomalies in Amorphous and Textured CoSi Semimetal Thin Films.

In recent times the chiral semimetal cobalt monosilicide (CoSi) has emerged as a prototypical, nearly ideal topological conductor hosting giant, topologically protected Fermi arcs. Exotic topological quantum properties have already been identified in CoSi bulk single crystals. However, CoSi is also known for being prone to intrinsic disorder and inhomogeneities, which, despite topological protection, risk jeopardizing its topological transport features.

Molecular electronic refrigeration against parallel phonon heat leakage channels.

Due to their structured density of states, molecular junctions provide rich resources to filter and control the flow of electrons and phonons. Here we compute the out of equilibrium current-voltage characteristics and dissipated heat of some recently synthesized oligophenylenes (OPE3) using the Density Functional based Tight-Binding (DFTB) method within Non-Equilibrium Green's Function Theory (NEGF). We analyze the Peltier cooling power for these molecular junctions as function of a bias voltage and investigate the parameters that lead to optimal cooling performance.

Thermal Simulation and Experimental Analysis of Optically Pumped InP-on-Si Micro- and Nanocavity Lasers.

There is a general trend of downscaling laser cavities, but with high integration and energy densities of nanocavity lasers, significant thermal issues affect their operation. The complexity of geometrical parameters and the various materials involved hinder the extraction of clear design guidelines and operation strategies. Here, we present a systematic thermal analysis of InP-on-Si micro- and nanocavity lasers based on steady-state and transient thermal simulations and experimental analysis.

Waveguide coupled III-V photodiodes monolithically integrated on Si.

The seamless integration of III-V nanostructures on silicon is a long-standing goal and an important step towards integrated optical links. In the present work, we demonstrate scaled and waveguide coupled III-V photodiodes monolithically integrated on Si, implemented as InP/InGaAs/InP p-i-n heterostructures. The waveguide coupled devices show a dark current down to 0.

Ultra-stable dry cryostat for variable temperature break junction.

We present the design of a variable temperature setup that uses a pulse tube cryocooler to perform break-junction experiments at variable temperatures ranging from 12 K to room temperature. The use of pulse tube coolers is advantageous because they are easy to use, can be highly automatized, and used to avoid wastage of cryogenic fluids. This is the reason why dry cryostats are conquering more and more fields in cryogenic physics.

Sondheimer oscillations as a probe of non-ohmic flow in WP crystals.

As conductors in electronic applications shrink, microscopic conduction processes lead to strong deviations from Ohm's law. Depending on the length scales of momentum conserving (l) and relaxing (l) electron scattering, and the device size (d), current flows may shift from ohmic to ballistic to hydrodynamic regimes. So far, an in situ methodology to obtain these parameters within a micro/nanodevice is critically lacking.

Coupled VO Oscillators Circuit as Analog First Layer Filter in Convolutional Neural Networks.

In this work we present an in-memory computing platform based on coupled VO oscillators fabricated in a crossbar configuration on silicon. Compared to existing platforms, the crossbar configuration promises significant improvements in terms of area density and oscillation frequency. Further, the crossbar devices exhibit low variability and extended reliability, hence, enabling experiments on 4-coupled oscillator.

Correction: Electronic conductance and thermopower of single-molecule junctions of oligo(phenyleneethynylene) derivatives.

Correction for 'Electronic conductance and thermopower of single-molecule junctions of oligo(phenyleneethynylene) derivatives' by Hervé Dekkiche et al., Nanoscale, 2020, 12, 18908-18917, DOI: 10.1039/D0NR04413J.

Spatially resolved thermoelectric effects in semiconductor-metal nanowire heterostructures.

The thermoelectric properties of a nanoscale germanium segment connected by aluminium nanowires are studied using scanning thermal microscopy. The germanium segment of 168 nm length features atomically sharp interfaces to the aluminium wires and is surrounded by an Al2O3 shell. The temperature distribution along the self-heated nanowire is measured as a function of the applied electrical current, for both Joule and Peltier effects.

Electronic conductance and thermopower of single-molecule junctions of oligo(phenyleneethynylene) derivatives.

We report the synthesis and the single-molecule transport properties of three new oligo(phenyleneethynylene) (OPE3) derivatives possessing terminal dihydrobenzo[b]thiophene (DHBT) anchoring groups and various core substituents (phenylene, 2,5-dimethoxyphenylene and 9,10-anthracenyl). Their electronic conductance and their Seebeck coefficient have been determined using scanning tunneling microscopy-based break junction (STM-BJ) experiments between gold electrodes. The transport properties of the molecular junctions have been modelled using DFT-based computational methods which reveal a specific binding of the sulfur atom of the DHBT anchor to the electrodes.

Author Correction: Topological matter: Shrewd detectives find a dissipation channel.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Thermal Transport through Single-Molecule Junctions.

Molecular junctions exhibit a rich and tunable set of thermal transport phenomena. However, the predicted high thermoelectric efficiencies, phonon quantum interference effects, rectification, and nonlinear heat transport properties of organic molecules are yet to be verified because suitable experimental techniques have been missing. Here, by combining the break junction technique with suspended heat-flux sensors with picowatt per Kelvin sensitivity, we measured the thermal and electrical conductance of single organic molecules at room temperature simultaneously.

Combined scanning probe electronic and thermal characterization of an indium arsenide nanowire.

As electronic devices are downsized, physical processes at the interface to electrodes may dominate and limit device performance. A crucial step towards device optimization is being able to separate such contact effects from intrinsic device properties. Likewise, an increased local temperature due to Joule heating at contacts and the formation of hot spots may put limits on device integration.

Experimental signatures of the mixed axial-gravitational anomaly in the Weyl semimetal NbP.

The conservation laws, such as those of charge, energy and momentum, have a central role in physics. In some special cases, classical conservation laws are broken at the quantum level by quantum fluctuations, in which case the theory is said to have quantum anomalies. One of the most prominent examples is the chiral anomaly, which involves massless chiral fermions.

Heat transport through atomic contacts.

Heat transport and dissipation at the nanoscale severely limit the scaling of high-performance electronic devices and circuits. Metallic atomic junctions serve as model systems to probe electrical and thermal transport down to the atomic level as well as quantum effects that occur in one-dimensional (1D) systems. Whereas charge transport in atomic junctions has been studied intensively in the past two decades, heat transport remains poorly characterized because it requires the combination of a high sensitivity to small heat fluxes and the formation of stable atomic contacts.

A robust molecular probe for Ångstrom-scale analytics in liquids.

Traditionally, nanomaterial profiling using a single-molecule-terminated scanning probe is performed at the vacuum-solid interface often at a few Kelvin, but is not a notion immediately associated with liquid-solid interface at room temperature. Here, using a scanning tunnelling probe functionalized with a single C60 molecule stabilized in a high-density liquid, we resolve low-dimensional surface defects, atomic interfaces and capture Ångstrom-level bond-length variations in single-layer graphene and MoS2. Atom-by-atom controllable imaging contrast is demonstrated at room temperature and the electronic structure of the C60-metal probe complex within the encompassing liquid molecules is clarified using density functional theory.

Nanoscale thermometry by scanning thermal microscopy.

Measuring temperature is a central challenge in nanoscience and technology. Addressing this challenge, we report the development of a high-vacuum scanning thermal microscope and a method for non-equilibrium scanning probe thermometry. The microscope is built inside an electromagnetically shielded, temperature-stabilized laboratory and features nanoscopic spatial resolution at sub-nanoWatt heat flux sensitivity.

Temperature mapping of operating nanoscale devices by scanning probe thermometry.

Imaging temperature fields at the nanoscale is a central challenge in various areas of science and technology. Nanoscopic hotspots, such as those observed in integrated circuits or plasmonic nanostructures, can be used to modify the local properties of matter, govern physical processes, activate chemical reactions and trigger biological mechanisms in living organisms. The development of high-resolution thermometry techniques is essential for understanding local thermal non-equilibrium processes during the operation of numerous nanoscale devices.