Ultrafast phase transitions induced by femtosecond light pulses present a new opportunity for manipulating the properties of materials. Understanding how these transient states are different from, or similar to, their thermal counterparts is key to determining how materials can exhibit properties that are not found in equilibrium. In this paper, we reexamine the case of the light-induced insulator-metal phase transition in the prototypical, strongly correlated material ${\mathrm{VO}}_2$, for which a nonthermal Mott-Hubbard transition has been claimed. Here, we show that heat, even on the ultrafast timescale, plays a key role in the phase transition. When heating is properly accounted for, we find a single phase-transition threshold corresponding to the thermodynamic structural insulator-metal phase transition, and we find no evidence of a hidden transient Mott-Hubbard nonthermal phase. The interplay between the initial thermal state and the ultrafast transition may have implications for other transient states of matter.

中文翻译：

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Vo2是否承载瞬态单斜晶金属相？

飞秒光脉冲引起的超快速相变为操纵材料的性能提供了新的机会。了解这些瞬态如何与它们的热对应物不同或相似，是确定材料如何表现出平衡中找不到的特性的关键。在本文中，我们重新检查了原型，强相关材料中光诱导的绝缘体-金属相变的情况${\mathrm{VO}}_2$，因此要求非热Mott-Hubbard跃迁。在这里，我们表明，即使在超快的时间尺度上，热量在相变中也起着关键作用。如果正确考虑了加热，我们会发现一个与热力学结构绝缘体-金属相变相对应的单一相变阈值，并且没有发现隐藏的瞬态Mott-Hubbard非热相的证据。初始热态和超快速转变之间的相互作用可能会对物质的其他瞬态产生影响。