Paper of the week: How polar is a liquid made only of ions?

With Mark Kobrak (J. Phys. Chem. B, 2004), I used molecular dynamics and the solvatochromic dye betaine-30 to probe polarity in room-temperature ionic liquids. The ionic solvent screens long-range electrostatics, so solvation is governed by local interactions, while thermal fluctuations create transient long-range interactions that may matter for reaction kinetics. Cited 140+ times. https://doi.org/10.1021/jp035891m

A Perovskite Synapse That Updates Linearly: 100 Conductance States and Attojoule-Scale Read Energy

Analog memristive synapses are only as good as their weight updates. If conductance changes are nonlinear or asymmetric, neural-network training suffers. A team at the University of Science and Technology Beijing reports a halide-perovskite synapse that makes these updates unusually linear.

The material is a two-dimensional alternating-cations-in-the-interlayer (ACI) perovskite, GAMA5Pb5I16, grown with additive engineering (MACl) and isopropanol-vapor annealing so that the crystals orient vertically between the electrodes. Because the film is a mixed ionic-electronic conductor, the voltage pulses move iodide ions and vacancies along the inorganic Pb–I framework, while the organic spacer suppresses migration across it (supported by DFT). The conductance therefore changes gradually through an interfacial valence-change mechanism rather than abrupt filament formation.

Key numbers from the paper: 100 discrete conductance states with nonlinearity of 0.027 (potentiation) and 0.064 (depression) and asymmetry of 0.037; with 50 states the nonlinearity is 0.010 and 0.012. The device reproduces paired-pulse facilitation (110% index) with fast and slow relaxation times of about 5 and 30 ms, similar to biological synapses. The read energy reaches 5.5 aJ at 0.05 V and 100 ns, versus 169.5 nJ for a 1.5 V, 100 µs programming pulse. An 8×8 crossbar array showed all 64 units switching.

In simulation, the measured conductance curves were used to constrain the weights of a YOLOv9-based vision network: object detection reached mAP50 of 57.6%, 98.1% of the 58.7% floating-point baseline. The authors stress that this is a software simulation based on a single device's curves, without device-to-device variation, endurance or drift.

Why it matters: the result shows that controlling ion transport by crystal orientation can make a soft, solution-processed material behave like a precise, tunable synapse for in-sensor computing.

Paper: Z. Sun et al., "Highly Linear Perovskite Synapses for Neuromorphic Computing," Advanced Science (2026), DOI: https://doi.org/10.1002/advs.78461

Physics community on Zenodo: open for submissions

Friends, our group "Physics" (Физика) now has its own community on Zenodo: https://zenodo.org/communities/physicsinrussian/ Everyone is welcome to share their work there: papers, preprints, reviews, lectures, teaching materials, problem sets, data, code, presentations and posters. Why it is useful • Every record gets a DOI, a permanent link you can cite in papers and in your CV. • Zenodo is run by CERN, so your work is stored reliably and permanently. • It is free: no submission or publication fees. • Records are discoverable via Google Scholar and OpenAIRE and can be linked to your ORCID. • You can upload new versions while keeping the DOI. • Not only papers: data, software and course materials are welcome too. • Publish in Russian, English or any other language. • A dated record helps establish the priority of an idea. What not to expect • There is no peer review yet. This is not a journal publication and does not count in Scopus or Web of Science. • Authors are responsible for the quality of their work; there is no editorial editing. • Posting on Zenodo usually does not prevent later journal submission, but check the specific journal's policy. What's next Submission is open now: create a record on Zenodo and choose the community "Физика" (physicsinrussian). In the future we plan to introduce peer review, so the community becomes a curated venue. Join, publish, and tell your colleagues!