The work, published in Nature Materials, focuses on freestanding membranes of BaTiO3, one of the most intensively studied ferroelectric compounds in existence. Ferroelectrics possess a spontaneous electric polarization that can be reoriented between stable states by an external field, which is precisely why they dominate applications ranging from capacitors to nonvolatile memories and piezoelectric transducers. What makes BaTiO3 particularly attractive for the new experiment is that its polar state is intimately tied to a structural distortion of the crystal lattice: below its Curie temperature, the titanium ions shift off-center within their oxygen cages, breaking the symmetry of the lattice and creating the electrical polarization. Because phonons are themselves collective motions of this lattice, any manipulation of the polarization necessarily reshapes the entire vibrational landscape, including the subtle rotational motions that define chiral phonons.

The particular vibration studied here belongs to what the authors describe as the g-wave sector of the lattice dynamics, referring to a high-frequency branch of phonons whose atoms execute circular, swirling trajectories. In such modes, two conjugate forms of the vibration exist, left-handed and right-handed, which are mirror images of one another but otherwise identical in energy. In an unperturbed crystal that lacks a handedness of its own, these two forms are degenerate, meaning they coexist in equal measure and no net chirality is expressed. To observe or use chiral phonons, one therefore needs a way to break this degeneracy, to make the crystal prefer one rotational sense over the other, and, crucially, to switch that preference on demand. The new study demonstrates that in BaTiO3 membranes, the ferroelectric polarization does exactly this job, acting as an internal, field-tunable chiral axis for the lattice.

Demonstrating such control experimentally is far from trivial. Chiral phonons vibrate at frequencies of terahertz order, far too fast for conventional spectroscopies to resolve directly, and their signatures are embedded deep within the vibrational spectrum of the crystal. The technique of choice in this study was circularly dichroic resonant inelastic X-ray scattering, an advanced synchrotron method that combines the momentum-resolving power of inelastic X-ray scattering with the chiral sensitivity of circularly polarized light. In this scheme, an incoming X-ray photon tuned to an absorption edge of a constituent atom transfers a well-defined portion of its energy and momentum to the lattice, exciting a specific phonon, and the scattered photon is analyzed for its energy loss. By measuring how efficiently the phonon is excited when the X-ray beam’s circular polarization is reversed, researchers can determine the phonon’s own handedness with remarkable selectivity, effectively interrogating the crystal with one rotating probe to detect rotating excitations.

Using this approach on their BaTiO3 membranes, the researchers recorded phonon spectra with circularly polarized X-rays tuned to the titanium absorption edge and observed a clear dichroic signal at the energy of the g-wave phonon. The sign of this signal, which encodes the phonon’s chirality, flipped when the ferroelectric polarization of the membrane was reversed by an applied electric field. This is the central experimental result: the handedness of the lattice vibration is not a fixed property of the material but a state that follows the polarization direction and can be rewritten at will. Because ferroelectric polarization is nonvolatile, retaining its orientation after the field is removed, the phonon chirality it selects is likewise nonvolatile, opening a conceptual pathway toward devices in which information is stored in the rotational sense of atomic motion rather than in charge, spin, or conventional polarization alone.

The physics underlying this switching can be understood through the lens of symmetry. In the ferroelectric phase of BaTiO3, the off-center displacement of the titanium ions lowers the crystal symmetry and establishes a polar axis, transforming the material from an achiral environment into one that distinguishes between clockwise and counterclockwise rotation along that axis. The g-wave phonon’s circular atomic trajectories then couple differently to this polar lattice depending on their handedness, lifting the degeneracy between the left- and right-handed forms and determining which one dominates the measured dichroic response. When the electric field reverses the polarization, the symmetry operation connecting the two states acts like a mirror that interchanges the two chiralities, and the phonon population follows. The experiment thus provides a direct, momentum-resolved picture of how a macroscopic order parameter in a ferroelectric governs the microscopic rotation of atoms, a connection that had been theorized but was extraordinarily difficult to verify until the advent of chiral-sensitive inelastic X-ray techniques.

The significance of the result extends well beyond barium titanate itself. Chiral phonons have been proposed as carriers of angular momentum that can be transferred to electron spins, as mediators of a phonon contribution to the Edelstein and inverse Edelstein effects, and as a route to phonon-controlled magnetism in so-called phonon-magnetic materials. They also underpin emerging proposals for chiral phononics, in which the handedness of vibrations serves as an information carrier immune to some of the noise and leakage channels that plague charge-based electronics. What all of these proposals require is an efficient, reversible, and preferably electrically driven mechanism for writing and erasing phonon chirality. The demonstration that a ferroelectric gate can fulfill this role in a technologically mature material suggests that such mechanisms are not exotic laboratory curiosities but achievable engineering primitives.

The choice of freestanding membranes as the sample geometry is also consequential. Thin, released membranes of complex oxides can sustain electric fields and strain states that are difficult to impose in bulk crystals, and their reduced thickness minimizes the absorption and scattering losses that complicate soft X-ray measurements. In the study, the membrane format allowed the researchers to apply the switching field while maintaining optical access for the resonant scattering experiment, and it is consistent with the broader trend of integrating oxide ferroelectrics into thin-film heterostructures for next-generation electronic devices. The combination of a classic ferroelectric, a state-of-the-art synchrotron probe, and device-relevant sample geometry gives the result an unusually direct line from fundamental symmetry physics to potential applications.

Looking forward, the findings raise a series of compelling questions. How fast can the phonon chirality follow the polarization during a switching event, and what transient chiral dynamics unfold in the intermediate states of a ferroelectric domain wall as it sweeps through the membrane? Can the same circularly dichroic scattering technique resolve the interaction between chiral phonons and other quasiparticles, such as magnons or excitons, in heterostructures that couple ferroelectric and magnetic orders? And can the electrically written chirality be read out by faster, more compact means, perhaps through chirality-dependent optical or transport responses, so that phonon-handedness memory could one day be integrated into practical circuitry? The present work does not answer all of these questions, but by establishing electric-field switching as an experimental reality, it converts many of them from speculation into concrete research programs.

For decades, ferroelectricity has been understood as the electric-field control of where atoms sit. This new result reframes that familiar story: in BaTiO3, the same field control extends to how atoms move, determining the rotational sense of their collective dance. The ability to write, erase, and read the chirality of a lattice vibration with a voltage transforms chiral phonons from a fascinating spectroscopic observation into a controllable degree of freedom of condensed matter. As synchrotron and free-electron laser facilities continue to sharpen the tools of chiral X-ray scattering, and as oxide membranes become ever more integrated into device architectures, the swirling, handed vibrations of crystals may soon find themselves at the heart of technologies that store data, process signals, and manipulate angular momentum in ways their discoverers never imagined.

Subject of Research: Electric-field control of chiral g-wave phonons in ferroelectric barium titanate membranes

Article Title: Electric-field switching of g-wave phonon chirality in ferroelectric BaTiO3

Article References: Grimes, M., Ueda, H., Allington, C. J., Romao, C. P., Kummer, K., Kaur, P., Wang, L.-S., Chang, Y.-W., Yang, J.-C., Huang, S.-W., & Staub, U. (2026). Electric-field switching of g-wave phonon chirality in ferroelectric BaTiO3. Nature Materials. https://doi.org/10.1038/s41563-026-02737-w

Image Credits: AI Generated

DOI: 10.1038/s41563-026-02737-w

Keywords: phonon chirality, ferroelectricity, BaTiO3, electric-field switching, resonant inelastic X-ray scattering, X-ray circular dichroism, chiral phonons, functional materials, lattice dynamics, nonvolatile memory, phononics, membranes

The chemistry focuses on α-silyl alcohols, a distinctive class of organosilicon compounds in which a silicon-containing group and a hydroxyl group are attached to the same carbon atom. These molecules are valuable because they can be converted into carbon-centered anions or radicals, highly reactive intermediates that enable the formation of new chemical bonds. Yet α-silyl alcohols are often difficult to prepare. Their synthesis may require several steps, strongly basic reagents, or organometallic compounds that tolerate only a limited range of functional groups.

For decades, the best-known application of α-silyl alcohols has been the Brook rearrangement. In this process, the silyl group migrates from carbon to oxygen, generating reactive intermediates that can participate in further transformations. Although the rearrangement has made α-silyl alcohols useful building blocks, the laborious preparation of the starting materials has restricted their broader adoption. “Chemists have utilized these compounds mainly in the Brook rearrangement,” explained Dr. Matsumoto. “Despite such a unique reactivity and utility, little attention has been paid to the tedious procedures required for their preparation.”

The Kanazawa team addressed this challenge by turning to hydrogen-atom transfer, or HAT. During HAT, a radical species removes a hydrogen atom from a molecule through homolytic bond cleavage. The process generates a new carbon-centered radical without requiring the carbon atom to lose a proton as it would in a conventional ionic reaction. The researchers designed a photocatalytic system capable of removing a hydrogen atom from an α-silyl alcohol, producing a radical at the carbon adjacent to the silyl and hydroxyl groups.

Once formed, that radical can add to an alkene, creating a new carbon–carbon bond and producing a functionalized α-silyl alcohol. The transformation therefore combines two operations in a single reaction: selective activation of a normally unreactive C–H bond and radical alkylation with an alkene partner. The products retain the carbon–silicon bond, preserving a valuable chemical handle for subsequent transformations.

The central challenge was chemoselectivity. Carbon–silicon bonds are generally considered more labile than many carbon–hydrogen bonds, particularly under conditions that generate reactive radicals or strongly polarized intermediates. An uncontrolled reaction could therefore break the C–Si bond instead of activating the desired C–H bond. In the new system, however, the researchers observed the opposite preference. The catalyst selectively promoted cleavage of the inert C–H bond while preserving the more vulnerable C–Si linkage.

This unusual selectivity depended on the structure of the phosphonium ylide. Phosphonium ylides are tunable compounds whose electronic and steric properties can be modified by changing the substituents surrounding the phosphorus center. The researchers synthesized and evaluated a series of ylide derivatives, searching for a catalyst that could balance hydrogen-abstraction ability, radical stability, and compatibility with visible-light photoredox chemistry. One tailored derivative displayed substantially greater activity and chemoselectivity than conventional HAT catalysts, according to Dr. Matsumoto.

The reaction operates under mild conditions and uses visible-light irradiation to drive the catalytic cycle. In the proposed mechanism, the organophotoredox catalyst absorbs light and participates in electron-transfer events that generate the active radical species. The phosphonium ylide then mediates hydrogen-atom transfer from the α-silyl alcohol. The resulting carbon-centered radical reacts with an alkene before the catalytic sequence is completed, delivering the alkylated product while avoiding destructive cleavage of the C–Si bond.

A broad substrate scope and high functional-group tolerance make the method particularly attractive for synthetic chemistry. Conventional approaches to similarly substituted alcohols often rely on strongly basic organometallic reagents, which can damage sensitive functional groups or require extensive protecting-group strategies. By contrast, the Kanazawa protocol provides a more direct way to elaborate α-silyl alcohols using readily modifiable reaction partners. The retained silicon group also offers a platform for later chemical transformations, allowing the products to be converted selectively into complex organosilicon structures or into other aliphatic alcohols.

The work suggests that phosphonium ylides may have a wider role in radical catalysis than previously recognized. Their structural flexibility provides a way to fine-tune reactions in which ordinary HAT catalysts lack sufficient control. By combining that tunability with visible-light photoredox activation, the researchers have created a strategy for making difficult carbon–carbon bonds while preserving a strategically useful silicon substituent. Published in ACS Catalysis on July 2, 2026, the study could open new routes to molecular architectures relevant to drug discovery, materials science, and the broader development of efficient, functionally tolerant synthetic methods.

Subject of Research: Selective α-C–H alkylation of α-silyl alcohols using hydrogen-atom transfer and visible-light photoredox catalysis.

Article Title: α-C–H Alkylation of α-Silyl Alcohols: Hydrogen Atom Transfer Catalysis Preserving Labile C–Si Bonds

News Publication Date: 2 July 2026

Web References: https://doi.org/10.1021/acscatal.6c03020

References: ACS Catalysis, “α-C–H Alkylation of α-Silyl Alcohols: Hydrogen Atom Transfer Catalysis Preserving Labile C–Si Bonds,” DOI: 10.1021/acscatal.6c03020.

Image Credits: Kanazawa University

Keywords

α-Silyl alcohols, carbon–hydrogen activation, carbon–silicon bonds, hydrogen-atom transfer, phosphonium ylides, photoredox catalysis, visible-light chemistry, radical chemistry, organic synthesis, alkene alkylation.