EDITORS' SUGGESTION
Nanomechanical resonators, nanoelectronic systems, amorphous solids, and dark matter searches have each been the subject of recent or proposed experiments at or below 1 mK, but achieving such low cryostat temperatures is challenging. The authors report the performance of an aluminum nuclear demagnetization refrigerator designed to facilitate access to microkelvin temperatures. They found the aluminum refrigerant is well-suited to continuous nuclear demagnetization refrigeration when its natural oxide layer is effectively removed in selected regions. These results will broaden the field of microkelvin physics, accelerating the rate of discovery and increasing its technological potential.
Matthias Raba et al.
Phys. Rev. Applied 22, 024027 (2024)
EDITORS' SUGGESTION
Scaling up cryogenic systems, like arrays of superconducting nanowire single-photon detectors (SNSPDs), requires developing cryogenic coprocessors to minimize the number of cables exiting the cryostat. This work addresses this challenge by demonstrating the ability to read out, process, encode, and store data from SNSPDs using integrated nanowire electronics. The authors design a digital counter based on nanocryotrons—three-terminal nanowire devices—to perform signal processing and digitization at low temperatures. These results suggest that nanowire coprocessors could be developed, which would benefit the application of SNSPD arrays and other superconducting platforms.
Matteo Castellani et al.
Phys. Rev. Applied 22, 024020 (2024)
EDITORS' SUGGESTION
Bulk acoustic wave (BAW) resonators that generate dynamic lattice strain are important for applications such as filters, sensors, and quantum control, but there is a lack of measurements available to quantify the strain directly. This study uses stroboscopic X-ray diffraction microscopy with correlated optical measurements on an ensemble of nitrogen-vacancy center defects to measure the dynamic strain in a diamond BAW resonator. This unique approach allows for directly imaging BAW resonator strain to improve fabrication and performance and for directly measuring important parameters of quantum defects to improve quantum control.
Anthony D’Addario et al.
Phys. Rev. Applied 22, 024016 (2024)
EDITORS' SUGGESTION
Perovskite solar cell performance is affected by the rate of charge-carrier transfer into the charge transport layers (CTLs) and interfacial recombination, but these are difficult to distinguish. This study distinguishes them using ultrafast spectroscopy combined with a charge-carrier dynamics model that includes the Coulombic forces arising from the selective extraction of charge carriers. The authors obtain extraction and interface recombination rate constants for three common CTLs and determine the perovskite’s ambipolar diffusivity. These results identify the performance-limiting properties, and could inform the design of superior materials that can be characterized with this method.
Edward Butler-Caddle et al.
Phys. Rev. Applied 22, 024013 (2024)
EDITORS' SUGGESTION
The cooling of levitated nanoparticles is a major step in optomechanics, aiming at both fundamental physics experiments and sensing applications, but using nonlinear cooling schemes and electro-optic modulation devices can significantly elevate the cost and complexity of the experiment. The authors implement a practical all-electrical controller capable of cooling the center-of-mass motion of a levitated nanoparticle to sub-Kelvin temperatures. When combined with improved vacuum and detection, this method can provide a simple and direct platform for three-dimensional near-ground-state cooling of the nanoparticle’s motional state.
Oscar Kremer et al.
Phys. Rev. Applied 22, 024010 (2024)
LETTER
The ability to simulate XY models of classical spins is rather important, since e.g. it is related to solving NP-hard optimization problems. This study uses a photonic simulator to realize XY Hamiltonians with arbitrary spin connections and coupling strengths. The key unit is an optical system for vector-matrix multiplication that can perform arbitrary transformations of complex matrices. The Berezinskii-Kosterlitz-Thouless transition and ground-state search of several XY models are demonstrated experimentally. Thus this Letter provides an effective alternative approach for investigating such models and solving continuous quadratic optimization problems with optical systems.
Jiayi Ouyang et al.
Phys. Rev. Applied 22, L021001 (2024)
EDITORS' SUGGESTION
Chirality can appear at many length scales in nature. In this study the authors introduce planar chirality as a quantitative geometric measure of chirality for two-dimensional objects. They apply this measure to evaluate the chirality of nanometer-sized structures with an electron microscope. They employ an innovative electron-optics device, the orbital-angular-momentum sorter, which applies a log-polar conformal mapping to the electron wave function and reaches near-optimal resolution in orbital angular momentum.
A.H. Tavabi et al.
Phys. Rev. Applied 22, 014083 (2024)
EDITORS' SUGGESTION
A promising branch of neuromorphic computing aims to perform cognitive operations in hardware, leveraging the physics of efficient and well-established nanodevices. This work presents a reconfigurable classifier, based on a network of magnetic tunnel junctions, that can learn to classify spoken vowels. In this task the hardware network surpasses multilayered software neural networks with the same number of trained parameters. These results, obtained using the same devices and working principle employed in industrial spin-transfer-torque magnetic random-access memory, constitute an important step toward the development of large-scale neuromorphic networks based on established technology.
A. López et al.
Phys. Rev. Applied 22, 014082 (2024)
NEWS AND COMMENTARY
