The new material is a chiral multiple quantum well structure built from layered two-dimensional halide perovskites. Quantum wells are thin sheets of semiconductor sandwiched between barriers, so thin that carriers are confined in one dimension and their electronic states become quantized, much like the discrete energy levels of an atom. In conventional perovskite quantum wells, each well has a fixed thickness determined by the organic spacer cations that separate the inorganic lead-halide sheets, and films typically contain a distribution of well widths, known as phases, coexisting within the same material. The researchers exploited this natural phase diversity deliberately: they constructed oriented films in which every quantum well phase, regardless of its width, is intrinsically chiral, meaning its structure lacks mirror symmetry and can exist in left- and right-handed forms.

Chirality is the key ingredient because of a phenomenon known as chiral-induced spin selectivity, or CISS, in which electrons of one spin orientation pass through a chiral structure far more readily than electrons of the opposite spin. The effect, long studied in DNA and other helical molecules, was demonstrated in chiral lead-halide perovskites in 2019, when spin-dependent charge transport through two-dimensional chiral hybrid perovskites was first reported. Subsequent work showed that a spin light-emitting diode operating at room temperature could be built from such materials, and in 2024 researchers demonstrated room-temperature spin injection across a chiral perovskite interface into a conventional III-V semiconductor. The bottleneck, as the new study emphasizes, is that spin polarization at the device level remains small because spins are lost rapidly at interfaces and in the bulk of the material, before they can accumulate or be extracted.

The team’s solution is conceptually elegant: instead of fighting spin relaxation at a single interface, they turn the whole layered structure into a spin cascade. Because the quantum wells in their film have varying widths, their electronic energy levels vary slowly and continuously across the different phases. Spatially, the wells of different widths are coupled to one another, so photoexcited carriers can funnel energetically downhill from wider-bandgap narrow wells into narrower-bandgap wide wells. Critically, because each well is chiral, every step along this energy descent is also a spin-selective polarization stage. Rather than generating spin polarization once and hoping it survives a perilous journey to a device contact, the structure regenerates and reinforces polarization at consecutive intermediate states, so that spin information is repeatedly refreshed as carriers move through the stack.

To build these structures, the researchers developed a seed-assisted crystallization process that forms the chiral multiple quantum wells in situ, producing oriented films in which the chirality is continuous across all quantum-well phases. They measured an average circular dichroism dissymmetry factor of 1.5 × 10⁻², a quantitative gauge of how differently the material absorbs left- and right-circularly polarized light, confirming that the chiral character is robust and uniform throughout the film rather than confined to one selected layer. This continuity is what distinguishes the new architecture from earlier chiral single quantum well designs, in which only one well width carried the chiral imprint and the surrounding achiral phases acted as spin sinks.

The consequence of the cascade is a dramatic extension of spin coherence. Using circularly polarized transient absorption spectroscopy, a pump-probe technique in which a spin-selective laser pulse tags the carrier population and a delayed probe tracks how long the spin imbalance persists, the team measured spin coherence lifetimes of approximately five nanoseconds at room temperature. In the world of spin physics, where room-temperature spin lifetimes in bulk halide perovskites have generally been measured in the sub-nanosecond to few-nanosecond range and can be far shorter in other solution-processed semiconductors, five nanoseconds is a meaningful reservoir of spin information, long enough for carriers to be transported, recombined or extracted with their polarization substantially intact.

The payoff appears directly in the light the material emits. The long-lived spin population produces circularly polarized luminescence with a luminescence dissymmetry factor of 1.4 × 10⁻², meaning the emitted light is measurably helical, carrying spin information encoded in the handedness of its polarization. Circularly polarized light is itself a valuable commodity: it is needed for spin-resolved displays, for optical communication schemes that encode data in polarization states, for quantum information protocols that use photon polarization as a qubit, and for chiral sensing, where the circular polarization of probe light interacts selectively with chiral molecules such as pharmaceuticals and biomolecules. Achieving strong, stable circular polarization from a solution-processable semiconductor at room temperature has been a persistent challenge.

The researchers also translated the long spin lifetime into working devices. Spin-dependent charge transport through the chiral films reached a polarization degree of over 80 percent, a figure indicating that the vast majority of transported carriers preserve their spin orientation, consistent with the CISS effect operating efficiently across the cascade structure. On this foundation the team demonstrated two applications. The first is X-ray-triggered dissymmetric photopolymerization, in which circularly polarized emission initiated by X-ray excitation drives a polymerization reaction in a way that distinguishes left- from right-handed product formation, a demonstration of how spin-polarized perovskites could influence chemical synthesis. The second is a circularly polarized light photodetector that the team reports as high-performing, converting the helicity of incoming light into an electrical signal.

What makes the advance notable from a materials chemistry standpoint is that it does not require exotic processing. Halide perovskites are celebrated for their solution processability and self-assembly, and the seed-assisted crystallization strategy harnesses the natural tendency of these materials to form multiple well-width phases, recruiting the phase mixture into functional service rather than suppressing it. The theoretical analysis provided by co-author Zhi-Gang Yu supports the picture of consecutive intermediate polarization states established by the slowly varying, spatially coupled wells, giving the empirical observations a coherent mechanistic framework rooted in the interplay of chirality-induced spin-orbit coupling and quantum confinement.

The broader implications reach into several converging fields. For chiroptical photonics, the work supplies a route to long-lived spin coherence in an easily processed material family, easing the construction of polarization-encoded light sources and detectors. For spintronics, it suggests that lossy interfaces, long the nemesis of spin injection, can be compensated architecturally by cascading many modest spin filters in series, a design principle transferable to other chiral semiconductors. And for perovskite research at large, it adds spin functionality to a material platform already excelling in solar cells, LEDs and radiation detectors. The authors frame the result as opening the way to long-lived spin coherence in halide perovskites and promoting their use in chiroptical and spintronic devices, and on the evidence presented, the five-nanosecond spin lifetime, the 80 percent transport polarization and the functional demonstrations together mark a substantial step toward spin-based technologies that operate not in cryogenic laboratories but at the temperatures of everyday life.

Subject of Research: Spin coherence extension in chiral perovskite multiple quantum wells via spin cascade

Article Title: Perovskite chiral multiple quantum wells with extended spin lifetime via efficient spin cascade

Article References: Qiu, J., Huang, Y., Wong, P. Y., Chang, K. T., Xue, J., Chen, Z., Wang, Z., Yao, J., Yu, Z.-G., Chen, X., & Lu, H. (2026). Perovskite chiral multiple quantum wells with extended spin lifetime via efficient spin cascade. Nature Photonics. https://doi.org/10.1038/s41566-026-02027-6

Image Credits: AI Generated

DOI: 10.1038/s41566-026-02027-6

Keywords: halide perovskites, chiral multiple quantum wells, spin cascade, spintronics, spin coherence lifetime, chiral-induced spin selectivity, circularly polarized luminescence, quantum wells, room-temperature spin, circularly polarized light photodetectors, Nature Photonics, Perovskite