Elastocaloric determination of the phase diagram of Sr2RuO4
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One of the main developments in unconventional superconductivity in the past two decades has been the discovery that most unconventional superconductors form phase diagrams that also contain other strongly correlated states. Many systems of interest are therefore close to more than one instability, and tuning between the resultant ordered phases is the subject of intense research1. In recent years, uniaxial pressure applied using piezoelectric-based devices has been shown to be a particularly versatile new method of tuning2,3, leading to experiments that have advanced our understanding of the fascinating unconventional superconductor Sr2RuO4 (refs.4–9). Here we map out its phase diagram using high-precision measurements of the elastocaloric effect in what we believe to be the first such study including both the normal and the superconducting states. We observe a strong entropy quench on entering the superconducting state, in excellent agreement with a model calculation for pairing at the Van Hove point, and obtain a quantitative estimate of the entropy change associated with entry to a magnetic state that is observed in proximity to the superconductivity. The phase diagram is intriguing both for its similarity to those seen in other families of unconventional superconductors and for extra features unique, so far, to Sr2RuO4.
Li , Y-S , Garst , M , Schmalian , J , Ghosh , S , Kikugawa , N , Sokolov , D A , Hicks , C W , Jerzembeck , F , Ikeda , M S , Hu , Z , Ramshaw , B J , Rost , A W , Nicklas , M & Mackenzie , A P 2022 , ' Elastocaloric determination of the phase diagram of Sr 2 RuO 4 ' , Nature , vol. 607 , no. 7918 , pp. 276-280 . https://doi.org/10.1038/s41586-022-04820-z
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DescriptionFunding: This work was supported by the Max Planck Society and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – TRR 288-422213477 ELASTO-Q-MAT (projects A10 (C.W.H. and A.P.M.), A11 (M.G.) and B01 (J.S.)). S.G. and B.J.R. acknowledge funding from the U.S. Department of Energy, Office of Basic Energy Sciences under award number DESC0020143. This work made use of the Cornell Center for Materials Research (CCMR) Shared Facilities, which is supported through the NSF MRSEC programme (no. DMR-1719875) (S.G. and B.J.R.). N.K. acknowledges support from KAKENHI Grants-in-Aid for Scientific Research (grant nos. 17H06136, 18K04715 and 21H01033) and Core-to-Core Program (no. JPJSCCA20170002) from the Japan Society for the Promotion of Science (JSPS) and by a JST-Mirai Program (grant no. JPMJMI18A3). A.W.R. acknowledges support from the Engineering and Physical Sciences Research Council (grant numbers EP/P024564/1, EP/S005005/1 and EP/V049410/1). Research in Dresden benefits from the environment created by the DFG Excellence Cluster ‘Correlations and Topology in Quantum Materials’.
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