无序促进铁磁性：Sr_{1-x} Ca_xRuO_3量子相变的圆化
Disorder promotes ferromagnetism: Rounding of the quantum phase transition in Sr_{1-x}Ca_xRuO_3
摘要：
随机性和量子涨落在低温下的微妙相互作用在从量子磁体和相关电子材料到超冷原子气体的系统中产生了大量的非常规现象。特别强的无序效应已被预测发生在零温度量子相变。在这里，我们证明了组成驱动的铁磁到顺磁量子相变在Sr 1-xCaxRuO 3是完全破坏通过引入的无序的随机分布的Sr和Ca离子的不同的离子半径。使用磁光技术，我们映射的组成温度空间中的磁相图。我们发现，铁磁相是显着扩展的无序，并制定了一个明显的尾巴在很宽的范围内的组合物x。这些发现被解释的微观模型的模糊量子相变巡回磁铁。此外，我们的理论研究表明，关联无序在促进铁磁性方面甚至比随机无序更强大。
英文摘要：
The subtle interplay of randomness and quantum fluctuations at low temperatures gives rise to a plethora of unconventional phenomena in systems ranging from quantum magnets and correlated electron materials to ultracold atomic gases. Particularly strong disorder effects have been predicted to occur at zero-temperature quantum phase transitions. Here, we demonstrate that the composition-driven ferromagnetic-to-paramagnetic quantum phase transition in Sr1-xCaxRuO3 is completely destroyed by the disorder introduced via the different ionic radii of the randomly distributed Sr and Ca ions. Using a magneto-optical technique, we map the magnetic phase diagram in the composition-temperature space. We find that the ferromagnetic phase is significantly extended by the disorder and develops a pronounced tail over a broad range of the composition x. These findings are explained by a microscopic model of smeared quantum phase transitions in itinerant magnets. Moreover, our theoretical study implies that correlated disorder is even more powerful in promoting ferromagnetism than random disorder.
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