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Multichannel coupling in hybrid systems makes an attractive testbed not only because of the distinct advantages entailed by each constituent mode but also because the opportunity to leverage interference among the various excitation pathways. Here, via combined analytical calculation and experiment, we demonstrate that the phase of the magnetization precession at the interface of a coupled yttrium iron garnet (YIG)/permalloy (Py) bilayer is collectively controlled by the microwave photon field torque and the interlayer exchange torque, manifesting a coherent, dual-channel excitation scheme that effectively tunes the magneto-optical spectrum. The different torque contributions vary with frequency, external bias field, and type of interlayer coupling between YIG and Py, which further results in destructive or constructive interferences between the two excitation channels, and hence selective suppression or amplification of the hybridized magnon modes. 

Improving the photon-magnon coupling strength can be done by tuning the structure of microwave resonators to better interact with the magnon counterpart. Planar resonators accommodating unconventional photon modes beyond the half- and quarter-wavelength designs have been explored due to their optimized mode profiles and potentials for on-chip integration. Here, we designed and fabricated an actively controlled ring resonator supporting the spoof localized surface plasmons (LSPs), and implemented it in the investigation of photon-magnon coupling for hybrid magnonic applications. We demonstrated gain-assisted photon-magnon coupling with the YIG magnon mode under several different sample geometries. The achieved coupling amplification largely benefits from the high quality factor (Q-factor) due to the additional gain provided by a semiconductor amplifier, which effectively increases the Q-factor from a nearly null state (passive resonance) to more than 1000 for a quadrupole LSP mode. Our results suggest an additional control knob for manipulating photon-magnon coupled systems exploiting external controls of gain and loss. 

Abstract The opto-electronic oscillators (OEOs) hosting self-sustained oscillations by a time-delayed mechanism are of particular interest in long-haul signal transmission and processing. On the other hand, owing to their unique tunability and compatibility, magnons—as elementary excitations of spin waves—are advantageous carriers for coherent signal transduction across different platforms. In this work, we integrated an opto-electronic oscillator with a magnonic oscillator consisting of a microwave waveguide and a yttrium iron garnet sphere. We find that, in the presence of the magnetic sphere, the oscillator power spectrum exhibits sidebands flanking the fundamental OEO modes. The measured waveguide transmission reveals anti-crossing gaps, a hallmark of the coupling between the opto-electronic oscillator modes and the Walker modes of the sphere. Experimental results are well reproduced by a coupled-mode theory that accounts for nonlinear magnetostrictive interactions mediated by the magnetic sphere. Leveraging the advanced fiber-optic technologies in opto-electronics, this work lays out a new, hybrid platform for investigating long-distance coupling and nonlinearity in coherent magnonic phenomena. 

Geometric diodes (GDs) represent a relatively unconventional class of diode that produces an asymmetric current response through carrier transport in an asymmetric geometry. Synthesized from the bottom up, Si nanowire‐based GDs are three‐dimensional, cylindrically symmetric nanoscale versions capable of room‐temperature rectification at GHz‐THz frequencies with near zero‐bias turn‐on voltages. Here, by fabricating three‐terminal n‐type Si nanowire GDs with axial contacts and an omega‐gate electrode, a distinct class of reconfigurable self‐switching geometric diodes (SSGDs) is reported. Single‐nanowire SSGD device measurements demonstrate a significant dependence of diode current and polarity on gate potential, where the diode polarity reverses at a gate potential of ≈−1 V under specific grounding conditions. Finite‐element modeling reproduces the experimental results and reveals that the gate potential—in combination with the morphology and dopant profile—produces an asymmetric potential along the nanowire axis that changes asymmetrically with axial bias, altering the effective conductive channel within the nanowire to yield diode behavior. The self‐switching effect is retained in two‐terminal SSGD devices, and modeling demonstrates that both three‐terminal and two‐terminal devices support rectification through THz frequencies. The results reveal a new mechanism of operation for nanowire‐based GDs and characterize a new type of self‐switching diode with reconfigurable polarity. 

Transition metal dichalcogenides (TMDCs) have garnered considerable interest over the past decade as a class of semiconducting layered materials. Most studies on the carrier dynamics in these materials have focused on the monolayer due to its direct bandgap, strong photoluminescence, and strongly bound excitons. However, a comparative understanding of the carrier dynamics in multilayer (e.g., >10 layers) flakes is still absent. Recent computational studies have suggested that excitons in bulk TMDCs are confined to individual layers, leading to room-temperature stable exciton populations. Using this new context, we explore the carrier dynamics in MoSe2 flakes that are between ∼16 and ∼125 layers thick. We assign the kinetics to exciton–exciton annihilation (EEA) and Shockley–Read–Hall recombination of free carriers. Interestingly, the average observed EEA rate constant (0.003 cm2/s) is nearly independent of flake thickness and 2 orders of magnitude smaller than that of an unencapsulated monolayer (0.33 cm2/s) but very similar to values observed in encapsulated monolayers. Thus, we posit that strong intralayer interactions minimize the effect of layer thickness on recombination dynamics, causing the multilayer to behave like the monolayer and exhibit an apparent EEA rate intrinsic to MoSe2. 

In this work, bottom‐up Al–Si–Al nanowire (NW) heterostructures are presented, which act as a prototype vehicle toward top‐down fabricated nanosheet (NS) and multi‐wire (MW) reconfigurable field‐effect transistors (RFETs). Evaluating the key parameters of these transistors regarding the on‐ and off‐currents as well as threshold voltages for n‐ and p‐type operation exhibit a high degree of symmetry. Most notably also a low device‐to‐device variability is achieved. In this respect, the investigated Al–Si material system reveals its relevance for reconfigurable logic cells obtained from Si NSs. To show the versatility of the proposed devices, this work reports on a combinational wired‐AND gate obtained from a multi‐gate RFET. Additionally, up‐scaling the current is achieved by realizing a MW RFET without compromising reconfigurability. The Al–Si–Al platform has substantial potential to enable complex adaptive and self‐learning combinational and sequential circuits with energy efficient and small footprint computing paradigms as well as for native components for hardware security circuits.