It was recently reported that a continuous electric current is a powerful control parameter to trigger changes in the electronic structure and metal–insulator transitions (MITs) in ${\mathrm{Ca}}_2{\mathrm{RuO}}_4$. However, the spatial evolution of the MIT and the implications of the unavoidable Joule heating have not been clarified yet, often hindered by the difficulty to assess the local sample temperature. In this work, we perform infrared thermal imaging on single-crystal ${\mathrm{Ca}}_2{\mathrm{RuO}}_4$ while controlling the MIT by electric current. The change in emissivity at the phase transition allows us to monitor the gradual formation and expansion of the metallic phase upon increasing current. Our local temperature measurements indicate that, within our experimental resolution, the MIT always occurs at the same local transition temperatures, irrespective of whether it is driven by temperature or current. Our results highlight the importance of local heating, phase coexistence, and microscale inhomogeneity when studying strongly correlated materials under the flow of electric current.

中文翻译：

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局部温度在Ca2RuO4电流驱动的金属-绝缘体转变中的作用

最近有报道说，连续电流是触发电子结构和金属-绝缘体转变（MIT）的强大控制参数。 ${钙}_2{O}_4$。但是，MIT的空间演变以及不可避免的焦耳热的影响尚未弄清，通常由于难以评估局部样品温度而受到阻碍。在这项工作中，我们对单晶进行红外热成像${钙}_2{O}_4$同时通过电流控制MIT。相变时发射率的变化使我们能够监视电流增加时金属相的逐渐形成和膨胀。我们的局部温度测量结果表明，在我们的实验分辨率范围内，MIT总是在相同的局部转变温度下发生，而不管它是由温度还是由电流驱动。我们的结果突出了研究电流下强相关材料时局部加热，相共存和微观不均匀性的重要性。