arXiv subjects

Tarek Moussa

Publications and source records attributed to Tarek Moussa.

3 recordsLinked to original sources

arXiv2026

Quantum sensing composite excitations in an anisotropic ferromagnet via a qubit

Ordered magnets harbor intrinsically squeezed ground states and magnonic excitations characterized by entanglement between spins and nonclassical magnon number composition. A pathway to detecting the superpositions of noneigenmode magnon number states underlying these nonclassical magnetic ground states has recently been demonstrated by utilizing a qubit coupled to the magnon mode via a direct dispersive interaction. Here, we theoretically develop this qubit spectroscopy further delineating the capabilities and limitations of this qubit spectroscopy for sensing the quantum superpositions that underlie the excited states. We demonstrate that the spectroscopy lends itself naturally to unraveling the superpositions that underlie the various quantized squeezed-magnon number states. However, excited states comprising superpositions of multiple squeezed Fock states become increasingly hard due to the large number of possible transitions, and resulting peaks, in the qubit spectroscopy thereby requiring qubits with narrower linewidths. Along the same lines, we theoretically demonstrate the qubit spectroscopy of a low amplitude coherent squeezed-magnon state analyzing the tradeoff between frequency crowding due to multiple transitions and peak linewidths. Our work lays the groundwork and design equations for deploying high-quality qubits towards sensing the composite nature of spin excitations in magnetic systems.

cond-mat.mes-hall↗

arXiv2026

Unquenched orbital angular momentum as the origin of spin inertia

The recent proposal and observation of spin inertia, and the consequent high-frequency spin nutation mode, have raised key questions for our understanding of magnetization dynamics, especially considering its high relevance for magnetic memories and ultrafast switching. Notwithstanding recent progress, a clear identification of spin inertia's physical origin thereby offering predictive power remains to be accomplished. Here, discussing general principles for identifying this physical origin, we examine unquenched orbital angular momentum (OAM) finding it to be a key candidate, despite its typically small value. Treating OAM and spin within a two-sublattice model, we derive the equivalent single-sublattice framework for magnetization dynamics making appropriate approximations. The latter naturally manifests the spin inertia term and parameter, which are otherwise introduced phenomenologically. The inertia parameter evaluated within our model is found to be in good agreement with its experimentally observed value in cobalt. We further delineate key experimental signatures that could verify or rule out the unquenched OAM as the origin of the observed high-frequency mode, and avoid a spurious optical mode in a two-sublattice ferromagnet from being identified as nutation. Our analysis offers a potential link between the recently emerged fields of orbitronics and spin inertia, thereby motivating investigations at their intersection.

cond-mat.mtrl-sci↗

arXiv2025

Magnon-polaron control in a surface magnetoacoustic wave resonator

Strong coupling between distinct quasiparticles in condensed matter systems gives rise to hybrid states with emergent properties. We demonstrate the hybridization of confined phonons and finite-wavelength magnons, forming a magnon-polaron cavity with tunable coupling strength and spatial confinement controlled by the applied magnetic field direction. Our platform consists of a low-loss, single-crystalline yttrium iron garnet (YIG) film coupled to a zinc oxide (ZnO)-based surface acoustic wave (SAW) resonator. This heterostructure enables exceptionally low magnon-polaron dissipation rates below $\kappa / 2\pi < 1.5\;$MHz. The observed mode hybridization is well described by a phenomenological model incorporating the spatial profiles of magnon and phonon modes. Furthermore, we report the first observation of Rabi-like oscillations in a coupled SAW-spin wave system, revealing the dynamical formation of magnon-polarons in the time domain. These results establish a platform for engineering hybrid spin-acoustic excitations in extended magnetic systems and enable time-resolved studies of magnon-polaron states.

cond-mat.mes-hall↗