Electric field switching of chiral phonons

summary

The gist

The gist: Electric-field switching of phonon angular momentum in ferroelectric BaTiO3 demonstrates a robust mechanism for non-volatile control of chiral phonons, showing reversible switching stable

In short

Researchers demonstrated that an electric field can switch the angular momentum of chiral phonons in BaTiO3, a ferroelectric material. Using circularly dichroic resonant inelastic X-ray scattering (CD-RIXS), they showed that applying a voltage reverses the phonon's circular dichroism contrast. This effect is robust and stable for over 15 hours, establishing a non-volatile method to control phonon chirality.

Key concepts

Chiral Phonons: These are lattice vibrations (phonons) that carry angular momentum because the atoms in the crystal break improper rotational symmetry. This asymmetry allows these vibrations to possess quantized angular momentum, enabling them to transfer this momentum through the lattice.
BaTiO3 (BTO): This is a polar ferroelectric titanate material used as a platform. Its key feature is that its polarization can be easily reversed by applying an external electric field. This makes it an ideal system for testing how symmetry breaking affects phonon properties.
Circular Dichroism (CD-RIXS): This is a specific type of X-ray scattering technique used to probe phonon angular momentum. It measures the difference in scattering intensity when using left-handed versus right-handed circularly polarized X-rays. The resulting contrast is sensitive to the chirality of the lattice vibrations.

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This episode discusses

The paper

Electric field switching of chiral phonons · Read on arXiv

Michael Grimes, Clifford J. Allington, Hiroki Ueda, Carl P. Romao, Kurt Kummer, Puneet Kaur, Li-Shu Wang, Yao-Wen Chang, Jan-Chi Yang,5, Shih-Wen Huang1, Urs Staub1

Center for Photon Science, Paul Scherrer Institut

Lattice vibrations carrying angular momentum, known as chiral phonons, have emerged as a promising route to control and understand complex material properties, yet their deterministic manipulation remains largely unexplored. Here we demonstrate electric-field switching of phonon angular momentum in the technologically relevant ferroelectric BaTiO3. Using circularly dichroic resonant inelastic X-ray scattering (CD-RIXS) at the oxygen K edge, we directly probe the phonon angular momentum and compare the measured dichroism with first-principles predictions of phonon-mode chirality. We find excellent agreement, revealing a momentum-dependent circular-dichroism contrast that exhibits a reversible gyroelectric effect, stable for at least 15 hours. Our results establish a robust mechanism for non-volatile control of chiral phonons and point towards new opportunities for phonon-based information and energy technologies.

DOI: 10.1038/s41563-026-02737-w

Transcript

Introduction to the show: ident: Quantum Radio. Generated commentary on the latest quantum physics and condensed matter papers.

Kai: Today's paper: "Electric field switching of chiral phonons".

Mira: The gist: Electric-field switching of phonon angular momentum in ferroelectric BaTiO3 demonstrates a robust mechanism for non-volatile control of chiral phonons, showing reversible switching stable for at least 15 hours.

Kai: First, who's behind it and why it matters.

Paper summary: Kai: So we've just heard that this paper by Grimes, Allington, et al. is about using an electric field to flip the angular momentum of phonons in BTO. What’s the core idea they are pushing here?

Mira: They are focusing on chiral phonons as a way to control material properties because these vibrations carry angular momentum and couple with spin and orbital degrees of freedom one <ref:2603.06144#pg1>. The thesis is that by using an electric field to invert the polarization direction in BTO, you can switch the handedness of the chiral modes.

Lev: If I'm running this on real hardware, I'd be looking at how sensitive this switching is to temperature fluctuations or noise; can we actually implement a system where this control persists?

Kai: The paper claims they use the room temperature tetragonal phase of BTO where inversion symmetry is already broken, and applying an electric field displaces the Ti4+ ion to a different stable site, which inverts the polarization.

Mira: Because that displacement changes how the oxygen octahedra move relative to each other, it flips the handedness of those chiral phonons as described by their C4v symmetry.

Lev: That sounds like a solid physical mechanism, but I'm wondering about the measurement itself; what exactly did they use to see this angular momentum change?

Kai: They used circularly polarised RIXS at the oxygen K edge to probe that phonon angular momentum directly, and they compared their measured dichroism with first-principles predictions for phonon-mode chirality.

Mira: The key finding is that the circular dichroism contrast in the RIXS measurement switches when you flip the direction of the electric poling field, which matches exactly what symmetry arguments predict should happen if the Ti4+ displacements are inverted.

Lev: So, to summarize for someone who only listens to this show: they showed you a physical way to turn off or on a specific type of lattice vibration using an electric field in BTO.

Kai: And beyond that, they confirmed this switching can happen non-volatily and last for at least fifteen hours, which is pretty significant for practical applications.

Conclusion: Mira: Thinking about the title, "Electric field switching of chiral phonons," it’s essentially taking a subtle symmetry property—chirality—and making it switchable with electricity.

Kai: It means we are moving beyond just controlling the frequency of vibrations, which is what standard phonon studies do; we're now talking about controlling the inherent handedness of the lattice motion itself.

Lev: From an error correction angle, if you can use an external field to flip a quantum degree of freedom tied to a vibrational mode, that opens up entirely new pathways for encoding information.

Mira: It points toward using these chiral phonons as tunable degrees of freedom in phononics, where the angular momentum isn't just fixed but can be actively manipulated by external stimuli.

Kai: This suggests we could integrate these phonon modes with other systems, maybe magnetic layers, to build things like on-chip phonon–magnon reservoirs for neuromorphic computing.

Lev: That integration would be interesting because it means you're using the crystal symmetry itself as a tunable switch for energy transfer between different physical phenomena.

Mira: So while they didn't solve everything about chiral phonons, this work proves that deterministic inversion of phonon angular momentum is possible in a technologically relevant perovskite over at least fifteen hours.

Kai: It’s a really concrete demonstration of how controlling the crystal symmetry via an electric field can manifest directly in the properties of the chiral phonons.

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