Magnetic tunnel junctions (MTJs) controlled by spin-transfer torque (STT) are key elements in nonvolatile memories and have recently been explored as stochastic devices in unconventional computing. The use of in-plane ferromagnetically coupled (FC) or antiferromagnetically coupled (AFC) synthetic free layers has been proposed for these applications, as it enables tuning of device performance and reliability. Until now, the effect of STT on the dynamics of FC and AFC free layers has remained controversial, yet clarifying this issue is increasingly important as STT-MTJ technologies evolve. In this study, we show an unambiguous comparison of the STT efficiency in FC and AFC synthetic free layers. This was enabled by a single measurement of a time-averaged response of superparamagnetic MTJs as a function of the applied current, unlike previous studies that measure the energy barrier and critical switching current independently. Despite the distinct magnetic configurations, we find indistinguishable STT efficiency between the two structures. This result indicates that interlayer mutual torque provides a negligible contribution within the experimentally accessible parameter range, while the torque from the reference layer dominates the STT effect on the synthetic free layers.

The development of miniaturized and mechanically flexible wearable optical health monitoring requires compact, biocompatible optoelectronic devices. Thin film devices based on perovskites, capable of both light emission and detection functionalities, offer a promising route toward such integrated systems. However, most reported dual-functional perovskite devices rely on toxic lead-based compositions, limiting their applications in skin-contact and wearable devices. Here, we demonstrate a lead-free tin-based perovskite dual-functional device, enabled by a synergistic dual-additive strategy to suppress defects and improve film crystallinity. The resulting device exhibits high-efficiency emission (radiance: 142 W m−2 sr−1, EQE: 7.56%) and sensitive photodetection (detectivity 1.53 × 1012 Jones). By integrating two perovskite diodes on a single flexible substrate, we realize a monolithic pulse sensor capable of real-time heart-rate monitoring. This work establishes a lead-free, flexible perovskite platform for bio-optoelectronic sensing, offering a promising pathway toward next-generation wearable healthcare systems.

Fundamental understanding of lattice softening and phonon transport in crystalline solids is crucial for thermoelectric applications, since the design of thermally insulating solids has gained significant interest over the years. In this work, we demonstrate strain induced lattice softening through negative thermal expansion (NTE) in Pr doped BiCuSeO, which breaks the theoretical Cahill limit, κlmin ∼ 0.55 W m−1 K−1, achieving a low κl of 0.24 W m−1 K−1 at 740 K. The Differential Scanning Calorimetry (DSC) and Raman analyses experimentally confirm NTE-driven lattice softening, which influences glass-like thermal transport beyond the theoretical limit. Meanwhile, the negative Gruneisen parameter (−1.13) calculated from reduced average sound velocity, νs∼1870 ms−1, with shrinkage of cell volume illustrates the NTE behavior. Furthermore, the observed weak carrier–phonon coupling μW/κl indicates the absence of conventional carrier scattering through NTE, which leads to a 54% increment in zT compared to undoped BiCuSeO (0.5 at 740 K) for Bi0.97Pr0.03CuSeO.

Scanning electrochemical cell microscopy (SECCM) utilizes a meniscus formed between the sample surface and the tip of a glass pipette filled with electrolyte as a confined electrochemical cell, enabling highly localized electrochemical measurement. However, SECCM alone makes it challenging to monitor chemical structure changes that accompany electrochemical reactions. In this study, we developed an in operando measurement system that integrates Raman spectroscopy with an electrochemical probe of the SECCM system, allowing simultaneous acquisition of localized electrochemical and spectroscopic data. A single crystal flakes of LiFePO4, a cathode material for lithium-ion batteries, was prepared, and changes in Raman scattering during lithium-ion charge/discharge processes were successfully monitored through the meniscus formed on their surfaces. This combined system provides nanoscale insights into electrochemical reactions and the associated structural transformations.

Two-dimensional (2D) boroxol-based B2O3 has recently been experimentally realized on metal substrates [Zio et al., Science 390, 95–99 (2025)], providing the first crystalline polymorph of B2O3 composed exclusively of boroxol units. However, the intrinsic structural stability and equilibrium geometry of freestanding 2D B2O3 remain unresolved. In this work, we investigate the intrinsic structural stability and physical properties of freestanding 2D boroxol-based B2O3 using first-principles calculations. While a perfectly planar monolayer is dynamically unstable, allowing spontaneous out-of-plane rippling stabilizes the lattice. The most stable rippled configuration lowers the total energy by ∼8 meV per B2O3 unit and satisfies both dynamical and elastic stability criteria. Rippling significantly modulates the electronic and mechanical properties: the indirect bandgap increases slightly, and the in-plane mechanical response becomes strongly anisotropic. Our results establish intrinsic rippling as a key stabilization mechanism in freestanding 2D B2O3 and provide guidance for its transfer, strain engineering, and mechanical tuning in boroxol-based 2D oxides.

We investigate Ti/HfO2 complementary resistive switching (CRS) devices using a three-terminal configuration that enables direct measurement of the voltage across each memristor during operation. The results show that the apparent shifts in the global CRS voltage response, observed with increasing sweep amplitude, originate from a voltage-divider effect produced by internal series resistance. At the same time, the intrinsic switching voltages of each memristor remain constant at ≈0.4–0.5 V. By isolating the response of each memristor, we obtain direct access to the local voltage drops and precisely identify the switching events of each element. Series resistance plays a decisive role, strongly influencing operating conditions and energy efficiency. These insights provide a robust physical framework for CRS dynamics and practical guidelines for optimizing current and voltage control in logic-in-memory circuits and selector-less crossbar arrays.

High-performance multispectral infrared photodetectors are essential for advanced imaging and sensing technologies. Here, we demonstrate a frequency division multiplexed (FDM) dual-band infrared phototransistor operating at 9.9 and 14.9 μm through a single source–drain channel. The device incorporates a double GaAs/AlGaAs quantum well (QW) structure, where two QWs of different thicknesses (7 and 11 nm) serve as charge-sensitive intersubband absorbers. Optical excitation at each wavelength induces opposite charge polarities on a floating gate, which are selectively demodulated by periodic resetting with distinct frequencies. This FDM operation enables simultaneous, independent readout of both spectral bands. Finally, we demonstrate absolute temperature sensing using the dual-band response, highlighting the device's potential for compact multispectral infrared sensing and imaging systems.

The anomalous valley Hall (AVH) effect, characterized by a polarized valley degree of freedom, provides a route toward a valley-dependent quantum anomalous Hall (QAH) state. Yet, realizing both in one material remains challenging due to their distinct Chern number requirements. We propose a general strategy for a strain-tunable topological transition in hexagonal ferromagnets. In the inversion-broken system, spin–orbit coupling yields valley polarization with valley-contrasted Chern numbers (C = ±1/2). Strain closes and reopens the gap at one valley, driving band inversion that switches the total Chern number to C = −1, transforming the system into a QAH phase with a single chiral edge channel. This strain-driven transition is demonstrated in monolayers of FeXY (X ≠ Y; Cl, Br, I), ScBr2, and VSi2P4. These results highlight the key role of strain engineering in controlling valley topology and provide a viable route toward valleytronic and topotronic applications.

Shortwave infrared (SWIR) detectors offer excellent penetration capabilities, making them highly valuable for applications such as target recognition and optical communication. However, traditional SWIR photodetectors suffer from high dark current, thermal noise, and the inability to resolve multidimensional information like polarization, making it challenging for highly sensitive and multidimensional sensing. Herein, we proposed a “symmetry breaking” principle to theoretically design an upconversion SWIR detector based on a silicon (Si) metasurface, which enables two-dimensional detection of light intensity and polarization information with high resolution and spectral tunability. By exciting a quasi-bound state in the continuum (quasi-BIC) mode with broken symmetry, this metasurface can achieve efficient third harmonic generation with an efficiency of 0.02%, which is seven orders of magnitude higher than that of the planar Si membrane. The efficient upconversion process increases the theoretical detectivity up to 7.9 × 1012 Jones in the SWIR band (1535.6 nm), comparable to that of commercially available InGaAs detectors. Benefiting from the filtering characteristics of the metasurface, the detector exhibits a response bandwidth of only 0.2 nm, making it one of the highest performance narrowband photodetectors in this spectral range. Furthermore, compared with conventional photodetectors, which only capture one-dimensional light intensity information, the third harmonic signal exhibits strong polarization sensitivity, which enables us to design a dual-dimensional optical communication system that doubles the data rate without additional readout time. This work provides a new technological pathway for the design of multiplexed high precision optical communication detectors.

Ultra-flexible perovskite solar cells (UF-PSCs) hold immense promise for wearable and aerospace applications, yet their development is limited by the intrinsic brittleness of perovskite films, which severely limits their mechanical durability under extreme bending on ultrathin substrates. To address this challenge, we develop a bulk stress-releasing and lattice-stabilization strategy by introducing benzyl benzylcarbamate (BBc) as a multifunctional additive. The carbonyl group in BBc exploits its negative electrostatic potential (−36.93 kcal mol−1) to form stable coordination bonds with undercoordinated Pb2+, simultaneously passivating defects and reinforcing mechanical integrity. Concurrently, benzyl groups dissipate stress through π–π interactions and act as steric cushions. As a result, rigorous bending tests demonstrate improved mechanical durability: devices on 5- and 10-μm substrates retain over 98% and 95% of their initial power conversion efficiencies (PCE), respectively, after 2000 and 5000 bending cycles. Furthermore, the modified UF-PSCs retain 90% of their initial PCE after strict crumpling tests, exhibiting excellent resistance to severe mechanical deformation. In addition, the incorporation of BBc enhances crystallinity, reduces defect density, and improves charge-carrier dynamics, yielding BBc-modified UF-PSCs with a notable PCE of 20.7% and an ultra-high power-to-weight ratio of 45.73 W g−1. This work establishes a targeted chemical reinforcement strategy to develop UF-PSCs with both high efficiency and mechanical robustness.