Colossal piezoresistance in narrow-gap Eu5In2Sb6

Piezoresistance, the change of the electrical resistance (R) of a material in response to an applied mechanical stress (σ), is the driving principle of electromechanical devices such as strain gauges, accelerometers, and cantilever force sensors. Enhanced piezoresistance has been traditionally observed in two classes of uncorrelated materials: nonmagnetic semiconductors and composite structures. We report the discovery of a remarkably large piezoresistance in Eu5In2Sb6 single crystals, wherein anisotropic metallic clusters naturally form within a semiconducting matrix due to electronic interactions. Eu5In2Sb6 shows a highly anisotropic piezoresistance, and uniaxial pressure along [001] of only 0.4 GPa leads to a resistivity drop of >99.95%, which results in a colossal piezoresistance factor of 5000×10-11Pa-1. Our result not only reveals the role of interactions and phase separation in the realization of colossal piezoresistance, but it also highlights a route to multifunctional devices with large responses to both pressure and magnetic field.