Nano Letters最新文献

Single-molecule magnets (SMMs) are molecules that can function as nanoscale magnets with potential use as magnetic memory bits. While SMMs can retain magnetization at low temperatures, characterizing them on surfaces and at room temperature remains challenging and requires specialized nanoscale techniques. Here, we use single nitrogen-vacancy (NV) centers in diamond as a highly sensitive, broadband magnetic field sensor to detect the magnetic noise of cobalt-based SMMs deposited on a diamond surface. We measured the NV relaxation and decoherence times at 296 K and at 5-8 K, observing a significant influence of the SMMs on them. From this, we infer the SMMs' magnetic noise spectral density (NSD) and underlying magnetic properties. Moreover, we observe the effect of an applied magnetic field on the SMMs' NSD at low temperatures. The method provides nanoscale sensitivity for characterizing SMMs under realistic conditions relevant to their use as surface-bound memory units.

Bilayer 3R-MoS₂ ferroelectric semiconductor field-effect transistors (FeSFETs) commonly attributed the device's ON-OFF switching to reversible transformation between up and down polarization, without considering the electronic properties of the domain walls (DWs) in MoS₂. In this work, we use density functional theory combined with nonequilibrium Green's function methods to show that DWs formation would induce electronic reconstruction at neighboring ferroelectric domains, thereby enhancing their polarization. We also found that local compressive strain in the DW can effectively increase the local conduction band minimum, drastically suppress the OFF-state current in FeSFETs. While pristine single-domain devices exhibit ON-OFF ratios of only 6.5 (armchair) and 3.8 (zigzag) at V_G = 0 V, junctions incorporating DWs can yield remarkably higher ratios of 99.1 and 33.5, respectively. This work establishes that enhanced polarization and suppressed conductance due to DWs present new avenues for improving the performance of MoS₂-based FeSFETs.

Altermagnets have attracted significant interest recently. Through the altermagnetic spin-splitting effect (ASSE), a longitudinal spin-polarized or a transverse pure spin current can be generated upon charge current injection. The ASSE is a key experimental feature for altermagnets but is often mixed with the spin Hall effect (SHE). Here, we present a comprehensive study of spin-to-charge conversion in epitaxial ruthenium dioxide (RuO₂) thin films using the ferromagnetic insulator yttrium iron garnet (YIG) as the spin current source. We conclusively show the absence of the ASSE in RuO₂ films grown with three different crystal orientations. Instead, we attribute the spin-to-charge conversion signals solely to the SHE. Moreover, we reveal a negative spin Hall angle in RuO₂ when it is adjacent to YIG, which reverses the sign when interfaced with Py. Our study provides crucial insights into the recent arguments on RuO₂ and advances the understanding of spin-to-charge conversion in low-symmetry materials.

Dynamic switching between daytime radiative cooling (DRC) and solar heating (SH), adapting to varying environmental conditions, offers an energy-saving and sustainable solution for all-seasonal thermal regulation of buildings and other outdoor facilities. However, many existing SH/DRC switchers can only alternate between high transmission and high reflection in the solar spectrum, hindering the effective harvesting of solar energy. Herein, by integrating the reversible metal electrodeposition technology and optical metamaterial absorber for the first time, we develop a novel device enabling in situ and active switching between SH/DRC states with a large modulation contrast of ΔA_sol = 0.82, whose superior performance is further validated by outdoor temperature measurements and building level energy-saving simulations. Our work not only opens new opportunities for thermal regulation devices and materials with higher environmental adaptability but also highlights the promising role of RMED in realizing highly efficient dynamic photonic devices.

Topological insulators lacking time-reversal symmetry can exhibit the quantum anomalous Hall effect. Odd-layer thick MnBi₂Te₄ is a promising platform due to its intrinsic magnetic nature; however, quantization is rarely observed in it. Our magnetoresistance measurements in the antiferromagnetic phase indicate, instead of a quantum anomalous Hall insulator, the presence of a trivial insulator state likely due to disorder, while in a high magnetic field, a Chern insulator state appears. From the magnetic field and temperature dependence, we estimate that the interlayer exchange coupling is enhanced by hydrostatic pressure while the intralayer coupling is weakened. The trivial band gap is also reduced, suggesting the role of disorder is weakened upon compression of the layers.

Helical spin textures in one-dimensional magnetic chains on superconductors can enable topological superconductivity and host Majorana zero modes, independent of the presence of intrinsic spin-orbit coupling. Here, we show that gadolinium (Gd) adatoms, possessing large 4f magnetic moments when placed on a Nb(110) surface, establish indirect exchange interactions mediated by valence electrons, manifesting as Yu-Shiba-Rusinov states. By combining scanning tunneling microscopy and spectroscopy with density functional theory, we analyze the emergence of the Yu-Shiba-Rusinov states in single Gd atoms and Gd dimers and uncover the underlying magnetic interaction mechanisms. Based in these results we predict by means of spin-dynamics simulations the formation of stable chiral Néel-type spin-spiral configurations in Gd chains. These findings highlight rare-earth magnets as a promising platform for precisely tuning spin-spiral ground states, an essential prerequisite for the realization of topological superconductivity.