  As device miniaturization approaches the atomic limit, it becomes highly
desirable to exploit novel paradigms for tailoring electronic structures and
carrier dynamics in materials. Elastic strain can in principle be applied to
achieve reversible and fast control of such properties, but it remains a great
challenge to create and utilize precisely controlled inhomogeneous deformation
in semiconductors. Here, we take a combined experimental and theoretical
approach to demonstrate that elastic strain-gradient can be created
controllably and reversibly in ZnO micro/nanowires. In particular, we show that
the inhomogeneous strain distribution creates an effective field that
fundamentally alters the dynamics of the neutral excitons. As the basic
principles behind these results are quite generic and applicable to most
semiconductors, this work points to a novel route to a wide range of
applications in electronics, optoelectronics, and photochemistry.
