Cable bacteria are multicellular microorganisms capable of charge transport over centimeter-scale distances through a network of conductive fibers embedded in the cell envelope. Understanding the charge injection mechanism into these fibers is essential to obtain a complete picture of their long-distance charge transport and a crucial step for their application in biobased electronics. To this aim, we fabricated “crosses” of two filaments, either native bacteria or extracted fiber skeletons, placed one on top of each other. By probing charge transport both through individual filaments and in cross-cable configurations, i.e., with current flowing from one filament to the other, it is possible to isolate the charge injection contribution. The results indicate that charge transfer between two contacting fibers is possible, albeit with increased resistance. We characterized the crosses at different temperatures, from 300 down to 50 K, observing thermally activated Arrhenius behavior both for single filaments and cross-conduction. The corresponding activation energy for filament-to-filament transport ranged from 15 to 40 meV, slightly smaller than that of individual cable bacterium filaments. We conclude that charge injection into the fibers must rely on the same mechanism as charge transport along the fibers. A structural model of the fibers is proposed in which internally winding conductive channels are embedded in a protein matrix. These channels can locally reach the surface of the fibers, where they can establish electrical contact with the external environment.

Particle exchange heat engines are a novel class of cyclic heat engines that are all-electrical, contain no moving parts and can therefore be scaled down to nanometer size. At the center of their operation is the manipulation of a particle flow between a hot and a cold reservoir through energy filtering mechanisms, where their efficiency depends primarily on the sharpness of the energy filter. In this study, we investigate the efficiency enhancement of such engines by utilizing ultra-sharp transmission resonances formed by magnetic impurities interacting with superconductors, known as Yu-Shiba-Rusinov bound states. To this end, we couple a neutral and stable diradical molecule to superconducting break-junction electrodes, and study its thermoelectric properties at ultra-low temperatures. By driving the molecular heat engine through a phase transition from a Kondo state into the Yu-Shiba-Rusinov regime, we observe a five fold increase in the thermoelectric power factor. This observation could pave the way for practical applications such as cryogenic waste heat recovery and efficient spot-cooling for future quantum computing architectures.

We experimentally and theoretically demonstrate that nonlinear spin-wave dynamics can induce an effective resonant interaction between nonresonant magnon modes in a yttrium iron garnet disk. Under strong pumping near the ferromagnetic resonance mode, we observe a spectral splitting that emerges with increasing drive amplitude. This phenomenon is well captured by a theoretical framework based on the linearization of a magnon three-wave mixing Hamiltonian, which at high power leads to parametric Suhl instabilities. The access and control of nonlinear magnon-parametric processes enable the development of experimental platforms in an unexplored parameter regime for both classical and quantum computation protocols.

Biotite crystals are phyllosilicate trioctahedral micas with the general chemical formula K(Mg,Fe)₃AlSi₃O₁₀(OH)₂ that form a solid-solution series with iron-poor phlogopite and iron-rich annite endmembers. With a wide band gap energy and a layered structure with free surface charges, biotite nanosheets can be readily obtained by cleavage methods and used as dielectrics in nanodevice fabrication for the next generation of electronics and energy harvesting. Here, a comprehensive study of biotite samples with different iron concentrations and oxidation states is presented. Structural, optical, magneto-optical, and magnetic characterizations were performed using several experimental techniques, including state-of-the-art synchrotron-based techniques, to correlate the iron chemistry (content and oxidation state) with the macroscopic properties of both minerals. The study reveals a nanoscale-homogeneous Fe distribution via synchrotron X-ray fluorescence mapping, defect-mediated optical transitions modulated by Fe³⁺/Fe²⁺ ratios, and temperature-dependent magnetic transitions from paramagnetism to competing ferro−/antiferromagnetic interactions. Furthermore, the use of these biotite crystals as substrates for ultrathin heterostructures incorporating monolayer (ML) MoSe₂ is explored by magneto photoluminescence at cryogenic temperatures. The results show that the presence of iron impurities in different oxidation states significantly impacts the valley properties for ML-MoSe₂. Overall, these findings offer a comprehensive interpretation of the physical properties of bulk biotites in a correlative approach, serving as a robust reference for future studies aiming to explore biotites in their ultrathin form.

van der Waals heterostructures (vdWHs) composed of transition-metal dichalcogenides (TMDs) and layered magnetic semiconductors offer great opportunities to manipulate the exciton and valley properties of TMDs. Here, we present magneto-photoluminescence (PL) studies in a WSe₂monolayer (ML) on a CrSBr crystal, an anisotropic layered antiferromagnetic semiconductor. Our results reveal the unique behavior of each of the ML-WSe₂PL peaks under a magnetic field that is distinct from the pristine case. An intriguing feature is the clear enhancement of the PL intensity that we observe each time the external magnetic field tunes the energy of an exciton in CrSBr into resonance with one of the optical states of WSe₂. This result suggests a magnetic field-controlled resonant energy transfer (RET) beyond other effects reported in similar structures. Our work provides deep insight into the importance of different mechanisms in magnetic vdWHs and underscores its great potential for light harvesting and emission enhancement of two-dimensional materials.

Organic radicals are promising candidates for molecular spintronics due to their intrinsic magnetic moment, their low spin-orbit coupling, and their weak hyperfine interactions. Using a mechanically controlled break junction setup at both room and low temperatures (6 K), we analyze the difference in charge transport between two nitronyl nitroxide radicals (NNR): one with a backbone in the para configuration, the other with a backbone in the meta configuration. We find that para-NNR displays a Kondo resonance at 6 K, while meta-NNR does not. Additionally, the observed Kondo peak in the differential conductance has a roughly constant width independent of the conductance, consistent with a scenario where the molecule is coupled asymmetrically to the electrodes.

A quantitative understanding of the microscopic mechanisms responsible for damping in van der Waals nanomechanical resonators remains elusive. In this work, we investigate van der Waals magnets, where the thermal expansion coefficient exhibits an anomaly at the magnetic phase transition due to magnetoelastic coupling. Thermal expansion mediates the coupling between mechanical strain and heat flow and determines the strength of thermoelastic damping (TED). Consequently, variations in the thermal expansion coefficient are reflected directly in TED, motivating our focus on this mechanism. We extend existing TED models to incorporate anisotropic thermal conduction, a critical property of van der Waals materials. By combining the thermodynamic properties of the resonator material with the anisotropic TED model, we examine dissipation as a function of temperature. Our findings reveal a pronounced impact of the phase transition on dissipation, along with transitions between distinct dissipation regimes controlled by geometry and the relative contributions of in-plane and out-of-plane thermal conductivity. These regimes are characterized by the resonant interplay between strain and in-plane or through-plane heat propagation. To validate our theory, we compare it to experimental data of the temperature-dependent mechanical resonances of FePS3 resonators.

The recent discovery of cable bacteria has greatly expanded the known length scale of biological electron transport, as these multi-cellular bacteria are capable of mediating electrical currents across centimeter-scale distances. To enable such long-range conduction, cable bacteria embed a network of regularly spaced, parallel protein fibers in their cell envelope. These fibers exhibit extraordinary electrical properties for a biological material, including an electrical conductivity that can exceed 100 S cm ⁻¹. Traditionally, long-range electron transport through proteins is described as a multi-step hopping process, in which the individual hopping steps are described by Marcus electron transport theory. Here, we investigate to what extent such a classical hopping model can explain the conductance data recorded for individual cable bacterium filaments. To this end, the conductive fiber network in cable bacteria is modelled as a set of parallel one-dimensional hopping chains. Comparison of model simulated and experimental current(I)/voltage(V) curves, reveals that the charge transport is field-driven rather than concentration-driven, and there is no significant injection barrier between electrodes and filaments. However, the observed high conductivity levels (>100 S cm ⁻¹) can only be reproduced, if we include much longer hopping distances (a > 10 nm) and lower reorganisation energies (λ < 0.2 eV) than conventionally used in electron relay models of protein structures. Overall, our model analysis suggests that the conduction mechanism in cable bacteria is markedly distinct from other known forms of long-range biological electron transport, such as in multi-heme cytochromes.

Helical molecules have been proposed as candidates for producing spin-polarized currents, even at room conditions, due to their chiral asymmetry. However, describing their transport mechanism in single molecular junctions is not straightforward. In this work, we show the synthesis of two novel kinds of dithia[11]helicenes to study their electronic transport in break junctions among a series of three helical molecules: dithia[n]helicenes, with n = 7, 9, and 11 molecular units. Our experimental measurements and clustering-based analysis demonstrate low conductance values that remain similar across different applied voltages and molecules. Additionally, we assess the length dependence of the conductance for each helicene, revealing an exponential decay characteristic of off-resonant transport. This behavior is primarily attributed to the misalignment between the energy levels of the molecule-electrodes system. The length dependence trend described above is supported by ab initio calculations, further confirming an off-resonant transport mechanism.

Heat transport in two dimensions is fundamentally different from that in three dimensions. As a consequence, the thermal properties of 2D materials are of great interest, from both scientific and application points of view. However, few techniques are available for the accurate determination of these properties in ultrathin suspended membranes. Here, we present an optomechanical methodology for extracting the thermal expansion coefficient, specific heat, and thermal conductivity of ultrathin membranes made of 2H-TaS₂, FePS₃, polycrystalline silicon, MoS₂, and WSe₂. The obtained thermal properties are in good agreement with the values reported in the literature for the same materials. Our work provides an optomechanical method for determining the thermal properties of ultrathin suspended membranes, which are difficult to measure otherwise. It provides a route toward improving our understanding of heat transport in the 2D limit and facilitates engineering of 2D structures with a dedicated thermal performance.

The layered metamagnet CrSBr offers a rich interplay between magnetic, optical, and electrical properties that can be extended down to the two-dimensional (2D) limit. Despite the extensive research regarding the long-range magnetic order in magnetic van der Waals materials, short-range correlations have been loosely investigated. By using small-angle neutron scattering (SANS) the formation of short-range magnetic regions in CrSBr with correlation lengths that increase upon cooling up to ≈3 nm at the antiferromagnetic ordering temperature (T _N ≈ 140 K) is shown. Interestingly, these ferromagnetic correlations start developing below 200 K, i.e., well above T _N. Below T _N, these correlations rapidly decrease and are negligible at low-temperatures. The experimental results are well-reproduced by an effective spin Hamiltonian, which pinpoints that the short-range correlations in CrSBr are intrinsic to the monolayer limit, and discard the appearance of any frustrated phase in CrSBr at low-temperatures within the experimental window between 2 and 200 nm. Overall, the obtained results are compatible with a spin freezing scenario of the magnetic fluctuations in CrSBr and highlight SANS as a powerful technique for characterizing the rich physical phenomenology beyond the long-range order paradigm offered by van der Waals magnets.