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Current-induced strong diamagnetism in the Mott insulator Ca2RuO4

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Science  24 Nov 2017:
Vol. 358, Issue 6366, pp. 1084-1087
DOI: 10.1126/science.aah4297

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Tuning diamagnetism with current

Properties of materials can be tuned by various means, such as chemical doping, magnetic field, or pressure. Sow et al. used electrical currents of modest density to turn the Mott insulator Ca2RuO4 into a semimetal. Concurrently, its diamagnetic response—the ability to counter an externally applied magnetic field—rose to levels higher than in any other nonsuperconducting material. The use of electrical current as a powerful experimental knob may be applicable to other similar materials.

Science, this issue p. 1084

Abstract

Mott insulators can host a surprisingly diverse set of quantum phenomena when their frozen electrons are perturbed by various stimuli. Superconductivity, metal-insulator transition, and colossal magnetoresistance induced by element substitution, pressure, and magnetic field are prominent examples. Here we report strong diamagnetism in the Mott insulator calcium ruthenate (Ca2RuO4) induced by dc electric current. The application of a current density of merely 1 ampere per centimeter squared induces diamagnetism stronger than that in other nonsuperconducting materials. This change is coincident with changes in the transport properties as the system becomes semimetallic. These findings suggest that dc current may be a means to control the properties of materials in the vicinity of a Mott insulating transition.

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