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Li YS, Garst M, Schmalian J, Ghosh S, Kikugawa N, Sokolov DA, Hicks CW, Jerzembeck F, Ikeda MS, Hu Z, Ramshaw BJ, Rost AW, Nicklas M, Mackenzie AP. Elastocaloric determination of the phase diagram of Sr 2RuO 4. Nature 2022; 607:276-280. [PMID: 35831597 PMCID: PMC9279151 DOI: 10.1038/s41586-022-04820-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 04/28/2022] [Indexed: 11/08/2022]
Abstract
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.
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Affiliation(s)
- You-Sheng Li
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
| | - Markus Garst
- Institut für Theoretische Festkörperphysik, Karlsruher Institut für Technologie, Karlsruhe, Germany
- Institut für QuantenMaterialien und Technologien, Karlsruher Institut für Technologie, Karlsruhe, Germany
| | - Jörg Schmalian
- Institut für QuantenMaterialien und Technologien, Karlsruher Institut für Technologie, Karlsruhe, Germany
- Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, Karlsruhe, Germany
| | - Sayak Ghosh
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA
| | - Naoki Kikugawa
- National Institute for Materials Science, Tsukuba, Japan
| | - Dmitry A Sokolov
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
| | - Clifford W Hicks
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
- School of Physics and Astronomy, University of Birmingham, Birmingham, UK
| | - Fabian Jerzembeck
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
| | - Matthias S Ikeda
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA, USA
- Department of Applied Physics, Stanford University, Stanford, CA, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Zhenhai Hu
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
| | - B J Ramshaw
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA
| | - Andreas W Rost
- Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
- Max Planck Institute for Solid State Research, Stuttgart, Germany
| | - Michael Nicklas
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany.
| | - Andrew P Mackenzie
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany.
- Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St Andrews, St Andrews, UK.
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Elastocaloric signature of nematic fluctuations. Proc Natl Acad Sci U S A 2021; 118:2105911118. [PMID: 34503998 DOI: 10.1073/pnas.2105911118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/24/2021] [Indexed: 11/18/2022] Open
Abstract
The elastocaloric effect (ECE) relates changes in entropy to changes in strain experienced by a material. As such, ECE measurements can provide valuable information about the entropy landscape proximate to strain-tuned phase transitions. For ordered states that break only point symmetries, bilinear coupling of the order parameter with strain implies that the ECE can also provide a window on fluctuations above the critical temperature and hence, in principle, can also provide a thermodynamic measure of the associated susceptibility. To demonstrate this, we use the ECE to sensitively reveal the presence of nematic fluctuations in the archetypal Fe-based superconductor Ba([Formula: see text])2[Formula: see text] By performing these measurements simultaneously with elastoresistivity in a multimodal fashion, we are able to make a direct and unambiguous comparison of these closely related thermodynamic and transport properties, both of which are sensitive to nematic fluctuations. As a result, we have uncovered an unanticipated doping dependence of the nemato-elastic coupling and of the magnitude of the scattering of low-energy quasi-particles by nematic fluctuations-while the former weakens, the latter increases dramatically with increasing doping.
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