An October 9 preprint from the University of Salerno in Italy and Helmholtz-Zentrum Dresden-Rossendorf in Germany reports enhanced nonlinear electrical transport in strained Bi₂Se₃ single-crystal slabs. The team created an inhomogeneous strain distribution by repeatedly cleaving macroscopic crystals and measured their second-harmonic electrical response. The arXiv paper has not yet undergone peer review.

The paper reports peak nonlinear responsivity on the order of 10⁴ micrometres per volt, which the authors compare with an approximately six-order-of-magnitude increase over Bi₂Se₃ thin films. They attribute the effect to classical geometric transport caused by strain gradients in the crystal bulk and discuss possible frequency upconversion and rectification. Although the response is strongest at 10 K, the paper reports a signal up to 200 K; it does not demonstrate a commercial converter device.