arXiv subjects

Yuanchen Deng

Publications and source records attributed to Yuanchen Deng.

11 recordsLinked to original sources

arXiv2026

Towards a monolithic platform for coupling superconducting circuits to low-loss microwave phonons in AlScN on 4H-SiC

Hybrid superconducting-phonon quantum processing is promising for cavity QED, measurement-based quantum computing, and other quantum applications. Relative to microwave photons at the same frequency, phonons can provide ultra-compact footprints, extremely low losses, and greater connectivity. Phonons can also couple strongly to superconducting circuits through the piezoelectric effect. However, this promise rests on scalable platforms that achieve these benefits without degrading superconducting circuit performance. This motivates a monolithic platform combining low phononic loss, strong electromechanical coupling, and superconducting-circuit compatibility without requiring suspended phononics. Here, we characterize a monolithic quantum acoustic platform combining aluminum superconducting circuits on exposed silicon carbide (SiC) with piezoelectric aluminum scandium nitride (AlScN) on SiC for integrated phononics. This architecture is enabled by selective removal of AlScN from selected chip regions, allowing aluminum superconducting microwave resonators to be fabricated directly on the SiC while preserving adjacent AlScN-on-SiC regions for phonon transduction. The resulting Al-on-SiC resonators exhibit a coherent lifetime of 2.9 {\mu}s, demonstrating compatibility with aluminum superconducting quantum devices. In parallel, cryogenic surface acoustic delay-line measurements on the retained AlScN-on-SiC regions show low phononic propagation loss at 4.05 GHz, corresponding to an estimated phonon lifetime of 7.6 {\mu}s. Together with a previously demonstrated electromechanical coupling coefficient of about 4.3% and a theoretical upper bound of 8%, these results establish Al-on-SiC/AlScN-on-SiC as a promising monolithic platform for integrating superconducting microwave circuits with piezoelectric phononic components for quantum acoustic networking and hybrid quantum systems.

quant-ph↗

arXiv2025

Strongly Electromechanical Coupled Phononic Waveguides in Aluminum Scandium Nitride on Silicon Carbide

Guided phonons have become an increasingly important platform for classical and quantum information processing. While conventional surface acoustic wave systems are typically only guided in the vertical direction, two-dimensionally confined waveguide systems offer significant advantages in terms of density of phononic circuit components and much higher intensities of strain and piezoelectric fields, which make them promising candidates for advancing acoustoelectric and quantum phononic applications. One such material system for generating and guiding phonons at gigahertz frequencies is AlScN on SiC, which can be synthesized by sputter depositing AlScN directly onto SiC wafers. The AlScN on SiC platform allows for tightly vertically confined acoustic modes with high electromechanical coupling, high speed of sound, and simple fabrication of strip and rib waveguides. Until now, this system has only been studied as a slab waveguide platform, i.e., without any lateral waveguiding. Here, we present a 2D-confined phononic waveguide architecture in AlScN on SiC with strongly electromechanically coupled modes that could serve as a platform for phononic routing, power-efficient active and nonlinear phononic devices such as amplifiers, mixers, and oscillators, as well as for interacting with quantum systems such as vacancy centers, charge carriers, photons, and spins. We study two distinct gigahertz frequency waveguide mode families using impedance matched interdigital transducers and characterize their electromechanical coupling and propagation losses. Additionally, we analyze how these waveguides could interact with various important quantum and classical systems that can be either embedded in SiC or heterogeneously integrated on the surface.

quant-ph↗

arXiv2023

Realization of a Z classified chiral-symmetric higher-order topological insulator in a coupling-inversion acoustic crystal

Higher-order topological band theory has transformed the landscape of topological phases in quantum and classical systems. Here, we experimentally demonstrate a two-dimensional (2D) higher-order topological phase (HOTP), referred to as the multiple chiral topological phase (MCTP), which is protected by a multipole chiral number (MCN). Our realization differs from previous HOTPs in that it possesses a larger-than-unity MCN, which arises when the nearest-neighbor couplings (NNCs) are weaker than long-range couplings (LRCs). Our phase has an MCN of 4, protecting the existence of 4 mid-gap topological corner modes (TCMs) at each corner. The multiple TCMs demonstrated here could lead to enhanced quantum-inspired devices for sensing and computing. Our study also highlights the rich and untapped potential of LRC manipulation for future research in topological phases.

cond-mat.mes-hall↗

arXiv2022

Tailoring Structure-borne Sound Through Bandgap Engineering in Phononic Crystals and Metamaterials: A Comprehensive Review

In solid state physics, a bandgap (BG) refers to a range of energies where no electronic states can exist. This concept was extended to classical waves, spawning the entire fields of photonic and phononic crystals where BGs are frequency (or wavelength) intervals where wave propagation is prohibited. For elastic waves, BGs are found in periodically alternating mechanical properties (i.e., stiffness and density). This gives birth to phononic crystals and later elastic metamaterials that have enabled unprecedented functionalities for a wide range of applications. Planar metamaterials are built for vibration shielding, while a myriad of works focus on integrating phononic crystals in microsystems for filtering, waveguiding, and dynamical strain energy confinement in optomechanical systems. Furthermore, the past decade has witnessed the rise of topological insulators, which leads to the creation of elastodynamic analogs of topological insulators for robust manipulation of mechanical waves. Meanwhile, additive manufacturing has enabled the realization of 3D architected elastic metamaterials, which extends their functionalities. This review aims to comprehensively delineate the rich physical background and the state-of-the art in elastic metamaterials and phononic crystals that possess engineered BGs for different functionalities and applications, and to provide a roadmap for future directions of these manmade materials.

physics.app-ph↗

arXiv2021

Observation of degenerate zero-energy topological states at disclinations in an acoustic lattice

Building upon the bulk-boundary correspondence in topological phases of matter, disclinations have recently been harnessed to trap fractionally quantized density of states (DoS) in classical wave systems. While these fractional DoS have associated states localized to the disclination's core, such states are not protected from deconfinement due to the breaking of chiral symmetry, generally leading to resonances which, even in principle, have finite lifetimes and suboptimal confinement. Here, we devise and experimentally validate in acoustic lattices a paradigm by which topological states bind to disclinations without a fractional DoS but which preserve chiral symmetry. The preservation of chiral symmetry pins the states at the mid-gap, resulting in their protected maximal confinement. The integer DoS at the defect results in two-fold degenerate states that, due to symmetry constraints, do not gap out. Our study provides a fresh perspective on the interplay between symmetry-protection in topological phases and topological defects, with possible applications in classical and quantum systems alike.

cond-mat.mes-hall↗

arXiv2021

Observation of higher-order exceptional points in a non-local acoustic metagrating

Higher-order exceptional points have attracted increased attention in recent years due to their enhanced sensitivity and distinct topological features. Here, we show that nonlocal acoustic metagratings that enable precise and simultaneous control over their muliple orders of diffraction, can serve as a robust platform for investigating higher-order exceptional points in free space. The proposed metagratings, not only could advance the fundamental research of arbitrary order exceptional points, but could also empower unconventional free-space wave manipulation for applications related to sensing and extremely asymmetrical wave control.

physics.app-ph↗

arXiv2021

Bilayer Photonic Graphene

Drawing inspiration from bilayer graphene, this paper introduces its photonic analog comprising two stacked graphene-like photonic crystals, that are coupled in the near-field through spoof surface plasmons. Beyond the twist degree of freedom that can radically alter the band structure of the bilayer photonic graphene, the photonic dispersion can be also tailored via the interlayer coupling which exhibits an exponential dependence on the distance between the two photonic crystals. We theoretically, numerically, and experimentally characterize the band structures of AA- and AB-stacked bilayer photonic graphene, as well as for twisted bilayer photonic graphene with even and odd sublattice exchange symmetries. Furthermore, we numerically predict the existence of magic angles in bilayer photonic graphene, which are associated with ultra-flat bands resulted from interlayer hybridization. Finally, we demonstrate that the bilayer photonic graphene at a particular twist angle satisfying even sublattice exchange symmetry is a high-order photonic topological insulator. The proposed bilayer photonic graphene could constitute a useful platform for identifying new quantum materials and inspiring next-generation photonic devices with new degrees of freedom and emerging functionality.

physics.app-ph↗

arXiv2020

Magic-angle Bilayer Phononic Graphene

Thanks to the recent discovery on the magic-angle bilayer graphene, twistronics is quickly becom11 ing a burgeoning field in condensed matter physics. This letter expands the realm of twistronics to acoustics by introducing twisted bilayer phononic graphene, which remarkably also harbors the magic angle, evidenced by the associated ultra-flat bands. Beyond mimicking quantum mechanical behaviors of twisted bilayer graphene, we show that their acoustic counterpart offers a considerably more straightforward and robust way to alter the interlayer hopping strength, enabling us to unlock magic angles (> 3 degrees) inaccessible in classical twisted bilayer graphene. This study, not only establishes the acoustical analog of twisted (magic-angle) bilayer graphene, providing a testbed more easily accessible to probe the interaction and misalignment between stacked 2D materials, but also points out the direction to a new phononic crystal design paradigm that could benefit applications such as enhanced acoustic emission and sensing.

cond-mat.mes-hall↗

arXiv2019

Space-Time Phononic Crystals with Anomalous Topological Edge States

It is well known that an interface created by two topologically distinct structures could host nontrivial edge states that are immune to defects. In this letter, we introduce a one-dimensional space-time phononic crystal and study the associated anomalous topological edge states. A space-decoupled time modulation is assumed. While preserving the key topological feature of the system, such a modulation also duplicates the edge state mode across the spectrum, both inside and outside the band gap. It is shown that, in contrast to conventional topological edge states which are excited by frequencies in the Bragg regime, the time-modulation-induced frequency conversion can be leveraged to access topological edge states at a deep subwavelength scale where the entire phononic crystal size is merely 1/5.1 of the wavelength. This remarkable feature could open a new route for designing miniature devices that are based on topological physics.

physics.class-ph↗

arXiv2019

Bending sound around sharp corners without using topological edge states

Routing and guiding acoustic waves around sharp corners without backscattering losses is of great interest in the acoustics community. Sonic crystals have been primarily utilized to design backscattering-immune waveguides. While conventional approaches use defects to guide waves, a considerably more sophisticated and robust approach was recently developed based on topological edge states. In this paper, we propose a radically different theoretical framework based on extremely anisotropic metamaterials for engineering backscattering-immune waveguides. We theoretically derived the exact condition for one-way wave propagation in zigzag paths, and identified a number of key advantages of the current design over topologically protected waveguides. While the theoretical underpinning is universal and is applicable to acoustic and electromagnetic waves, the experimental validation was conducted using spoof surface acoustic waves. The proposed metamaterial could open up new possibilities for wave manipulation and lead to applications in on-chip devices and noise control.

physics.app-ph↗

arXiv2017

Zone folding induced topological insulators in phononic crystals

This letter investigates a flow-free, pseudospin-based acoustic topological insulator. Zone folding, a strategy originated from photonic crystal, is used to form double Dirac cones in phononic crystal. The lattice symmetry of the phononic crystal is broken by tuning the size of the center "atom" of the unit cell in order to open the nontrivial topological gap. Robust sound one-way propagation is demonstrated both numerically and experimentally. This study provides a flexible approach for realizing acoustic topological insulators, which are promising for applications such as noise control and waveguide design.

cond-mat.mes-hall↗