Research Briefing

Radiofrequency tuning elements made of quantum paraelectric materials are demonstrated at temperatures close to absolute zero — a temperature regime in which conventional electronic tuning components do not work. This advance greatly improves the read-out sensitivity of quantum circuits that require operation at such low temperatures.

Designing a rectifier for harvesting low ambient radiofrequency energy and converting it into useful d.c. power is challenging. Now, a spin-rectifier-based rectenna and a spin-rectifier array with on-chip coplanar waveguides are designed for harvesting ambient radiofrequency signals with good sensitivity and efficiency.

Graphene plasmon polaritons are expected to enable rapid data transfer and processing; however, these plasmons are difficult to access. Terahertz electronics now facilitate the efficient generation, manipulation and on-chip detection of wave packets lasting as little as 1.2 ps. This advance could lead to the development of nanoscale terahertz circuits.

A methodology — called auto tiny classifiers — is proposed to directly generate predictor circuits for the classification of tabular data, searching over the space of combinational logic using an evolutionary algorithm to maximize training prediction accuracy. Prediction performance is comparable to typical machine learning methods, but substantially fewer hardware resources and power are required.

The quantum anomalous Hall effect holds promise for quantum resistance metrology, but has been limited to low operating currents. A measurement scheme that increases the effect’s operational current is now demonstrated — a scheme that could also be used more generally to improve the performance of existing primary quantum standards of resistance based on the conventional quantum Hall effect.

A flexible, biodegradable and self-powered electronic bandage is designed to deliver dual-mode electrical stimulation, which can synergistically accelerate local intestinal wound healing. This approach also shows promise for reducing postoperative complications and could have broad potential for application in other tissues and organs.

Distributed sensing of a dynamic environment is typically characterized by the sparsity of events, such as neuronal firing in the brain. Using the brain as inspiration, an event-driven communication strategy is developed that enables the efficient transmission, accurate retrieval and interpretation of sparse events across a network of thousands of wireless microsensors.

An approach to dynamically control the photoresponsivity of pixels in a computational sensor based on local image gradients enables the precise and robust detection of edge features of targets in dim light conditions from a single image capture.

The planar structure of thin-film piezoelectric resonators limits the integration of multiband processors on a single chip. A three-dimensional nanomechanical resonator based on conformal ferroelectric gates to excite resonance in scalable silicon fins is shown to enable multiband integration on a single chip and to facilitate densification of processors for ultrawide-band wireless communication.

For a long time, spin–orbit coupling in bismuthates has been considered to be negligible; however, giant charge-to-spin conversion has now been observed in Ba(Pb,Bi)O₃-based heterostructures. These observations provide a path toward investigating the interplay of hidden spin–orbit phenomena and superconductivity.

A polymer-free method for stacking 2D materials has been demonstrated, using a cantilevered transfer support made from metallized silicon nitride. The assembly process, which is compatible with ultrahigh-vacuum operation, results in atomically clean and uniform interfaces.

A silicon photonics modulator design approach is proposed, in which the inductive networks and termination resistors are designed in conjunction with the optical phase shifter. A complementary metal–oxide–semiconductor (CMOS) silicon photonics transmitter developed with this approach achieved 112 gigabaud transmission with an energy efficiency better than 1 pJ per bit.

External-magnetic-field-free switching of the perpendicular magnetic anisotropy in magnetic layers is a prerequisite for the wide adoption of spintronic devices. This challenge could be met by the Weyl semimetal TaIrTe₄, which is now shown to generate an out-of-plane polarized spin current at room temperature.

Machine-learning-driven atomistic simulations are shown to describe phase-change materials on the length scale of real devices. This demonstration suggests that the atomic-scale design of phase-change architectures, programming conditions and full devices could be within reach.

The remarkable properties of graphene nanoribbons are promising for use in quantum technologies. To create quantum devices, however, individual nanoribbons must be contacted. This crucial step has now been demonstrated using single-walled carbon nanotubes as electrodes.

The use of topological spin structures is restricted by their limited scale, thermal stability or magnetic field requirements. A high-magnetic-field-assisted growth approach overcomes these limitations, enabling the construction of millimetre-scale meron lattices. These lattices were used to demonstrate chirality transfer from topologically protected quasiparticles to electrons and then photons.

Stacking a bilayer of chromium triiodide, a layered antiferromagnet, onto another with a twist angle gives rise to a moiré magnet with rich magnetic phases, including ferromagnetic and antiferromagnetic orders. The magnetic orders can be controlled through the twist angle, temperature and electrical gating, with the system also showing voltage-assisted magnetic switching.

The negative differential capacitance (NDC) of ferroelectrics could be used to reduce the energy consumption of ultra-scaled logic devices. An NDC phenomenon in ultrathin ferroelectric zirconium-doped hafnia is demonstrated. Field-effect transistors incorporating this ferroelectric in the gate stack display enhanced on-currents and reduced off-currents compared with conventional analogues, as well as tunable and enduring NDC.

Despite advances in speech processing systems, such as those used in voice-controlled devices, human hearing still outperforms technical systems in noisy and variable environments. To close this gap, a bioinspired acoustic sensor with integrated signal processing was developed — the dynamic microelectromechanical system (MEMS)-based cochlea.

A spoof surface plasmonic neural network with programmable weights and activation functions was proposed, which has the potential to achieve processing speeds close to the speed of light. This neural network was used to create a wireless communications system that can detect and process electromagnetic waves.