🔬 mesoscale physics

Experimental Realization of Synthetic Magnonic Lattice via Floquet Engineering

This paper demonstrates the experimental realization of a reconfigurable synthetic magnonic lattice in a single yttrium iron garnet device by using Floquet engineering to couple multimode resonances, thereby enabling scalable, high-dimensional magnonic dynamics without increasing the physical footprint.

Original authors: Amin Pishehvar, Jayakrishnan M. P. Nair, Zhaoyou Wang, Zixin Yan, Yu Jiang, Liang Jiang, Benedetta Flebus, Xufeng Zhang

Published 2026-07-01

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CC BY 4.0

Original authors: Amin Pishehvar, Jayakrishnan M. P. Nair, Zhaoyou Wang, Zixin Yan, Yu Jiang, Liang Jiang, Benedetta Flebus, Xufeng Zhang

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you have a musical instrument, like a guitar, but instead of strings, it has a special magnetic film. When you "pluck" this film with a magnetic field, it vibrates in specific patterns called magnons (think of these as sound waves traveling through the magnet).

Usually, to build a complex computer or processor using these waves, you would need to build a massive, intricate maze of physical tracks on a chip to guide the waves. The problem is that the best material for this (a crystal called YIG) is very hard to carve into tiny shapes. It's like trying to build a detailed city out of a block of diamond; it's too tough to cut.

The Big Idea: The "Virtual" Highway
This paper presents a clever workaround. Instead of building a bigger physical maze, the researchers created a "synthetic dimension."

Think of it like this:

The Old Way: To get from City A to City B, you have to drive a long physical road.
The New Way: You stay in the same spot, but you use a magical elevator that instantly moves you to different "floors" (frequencies) of the same building. Even though you haven't moved physically, you have traveled through a new, virtual space.

In this experiment, the "floors" are different vibration frequencies of the magnetic film. The researchers used a special technique called Floquet Engineering (which is just a fancy way of saying "shaking the system in a rhythmic pattern") to connect these different floors.

How They Did It: The Rhythmic Shaker

The Stage: They took a tiny, flat piece of YIG crystal. Because it's a finite size, it naturally supports a series of distinct vibration modes (like the different notes a drum can make).
The Connection: They attached a small coil to the setup and sent a rhythmic magnetic "shake" (a modulation signal) through it.
The Magic: When the rhythm of the shake matched the gap between two vibration notes, the notes started talking to each other. Energy could flow from one "floor" to the next.

By doing this, they turned a single, static piece of material into a reconfigurable lattice (a grid of connected points) that exists in the "frequency domain" rather than physical space.

What They Saw: The "Bloch Oscillation"
The most exciting part of their discovery was watching something called Bloch Oscillation.

Imagine you are walking up a staircase. Usually, you just keep going up. But in this synthetic world, because the "steps" (the gaps between frequencies) aren't perfectly even, the energy doesn't just march forward. Instead, it gets pushed back and forth, like a ball rolling up a hill, stopping, and rolling back down, then up again.

The Result: They excited one specific vibration mode and watched the energy dance back and forth between neighboring modes in this virtual grid.
Why it matters: This proves they can control how information moves through this synthetic space without needing to build a larger physical device. It's like having a super-complex circuit board that fits inside a single, tiny grain of sand.

The Takeaway
The researchers successfully built a "virtual city" inside a single magnetic chip. They showed that by shaking the chip at the right rhythm, they can make different vibration modes talk to each other, creating a programmable, high-dimensional system.

This is the first time this has been done with magnons. It means that in the future, we might be able to build complex, high-speed magnetic computers that don't need to be physically huge or difficult to manufacture, because the complexity exists in the "virtual" frequency space they created.

Technical Summary: Experimental Realization of Synthetic Magnonic Lattice via Floquet Engineering

Problem Statement
Magnonics, the study of spin-wave excitations in magnetic materials, offers a promising platform for coherent information processing due to low dissipation, strong nonlinearities, and intrinsic nonreciprocity. However, scaling magnonic circuits remains a significant bottleneck. While magnetic alloys are easily patterned, they suffer from high damping. Conversely, low-loss magnetic insulators like yttrium iron garnet (YIG) are difficult to pattern using conventional techniques due to their complex crystalline structures and resilience to chemical etching. These fabrication constraints hinder the development of scalable architectures and limit access to advanced functionalities such as programmable interactions and topological transport.

Methodology
To overcome these scaling limitations, the authors implement a "synthetic dimension" approach within a single YIG device. Instead of physically patterning a complex lattice, they utilize the frequency domain as a synthetic spatial dimension.

Device: The experiment utilizes a single-crystalline YIG film (23 µm × 2 mm × 3 mm) biased by an external magnetic field. Due to the finite chip size, the system supports a series of discrete standing wave magnetostatic surface spin waves (MSSWs) along the short edge.
Floquet Engineering: The authors apply time-periodic modulation to the bias magnetic field using a MHz-frequency drive coupled via a coil and a tunable LC resonator. This modulation induces coupling between discrete magnon modes in the frequency domain.
Theoretical Framework: The system is modeled using the Landau-Lifshitz-Gilbert (LLG) equation. Linearization yields a tight-binding Hamiltonian in a rotating frame, where the drive frequency ( $\Omega$ ) creates nearest-neighbor coupling ( $g_n$ ) between magnon modes ( $n$ and $n+1$ ). The coupling strength is governed by the Bessel function $J_1(\Delta/\Omega)$ , where $\Delta$ is the frequency deviation induced by the drive.
Measurement: The team employs time-resolved band structure spectroscopy and steady-state reflection measurements using a vector network analyzer (VNA) to map the Floquet band structure and observe inter-mode dynamics.

Key Contributions and Results

First Experimental Realization: This work presents the first experimental realization of a synthetic dimension in a magnonic system. It demonstrates that high-dimensional magnonic dynamics can be achieved within a compact device footprint without increasing physical complexity.
Reconfigurable Mode-Space Lattice: The system forms a reconfigurable lattice where interactions between discrete modes are electronically tunable. By adjusting the bias magnetic field, the authors can continuously shift the entire set of discrete modes and tune the mode spacing ( $\delta_n$ ), allowing for on-demand selection of the Floquet drive frequency to achieve selective mode coupling.
Observation of Strong Coupling and Dark States:
- The researchers observed clear inter-mode coupling, evidenced by the splitting of reflection spectra. At a drive amplitude of 250 mV, the coupling strength ( $g_3/2\pi \approx 10.5$ MHz) exceeded the dissipation rates of the involved modes, confirming the strong coupling regime with a cooperativity of $C=53$ .
- The system exhibited magnon dark modes, where specific sideband combinations remained decoupled from the central mode, rendering them invisible in the spectrum.
Spectral Bloch Oscillations: A hallmark of synthetic dimensions, the authors observed spectral Bloch oscillations. By exciting a specific mode (Mode 4) and applying the Floquet drive, they observed periodic energy exchange between Mode 4 and its nearest neighbors (Modes 3 and 5). The oscillation period depended on the drive strength, consistent with theoretical predictions of coherent information propagation in the synthetic frequency dimension.
Tunability: Unlike photonic or acoustic synthetic dimensions where lattices are fixed by geometry, this magnonic system offers unprecedented tunability. The mode spacing decreases with frequency, and the bias field allows for continuous adjustment of both the mode frequencies and the required drive frequency.

Significance
The paper claims that this advancement establishes synthetic dimensions as a scalable and programmable route for integrated magnonic technologies. By decoupling the complexity of the lattice from the physical device footprint, this approach enables the engineering of emergent phenomena that are inaccessible at equilibrium. The demonstrated ability to achieve complex, high-dimensional dynamics in a single, compact YIG device positions magnonic systems as viable platforms for advanced signal processing and the exploration of non-equilibrium physics, offering a complementary technology to electronics and photonics.

Technical Summary: Experimental Realization of Synthetic Magnonic Lattice via Floquet Engineering

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