Thermodynamic evidence for a nematic phase transition at the onset of the pseudogap in YBa2Cu3Oy


A long-standing controversial issue in the quest to understand the superconductivity in cuprates is the nature of the enigmatic pseudogap region of the phase diagram1. Especially important is whether the pseudogap state is a distinct thermodynamic phase characterized by broken symmetries below the onset temperature T. Here we report torque-magnetometry measurements of anisotropic susceptibility within the ab planes in orthorhombic YBa2Cu3Oy with exceptionally high precision. The in-plane anisotropy displays a significant increase with a distinct kink at the pseudogap onset temperature T, showing a remarkable scaling behaviour with respect to T/T in a wide doping range. Our systematic analysis reveals that the rotational symmetry breaking sets in at T in the limit where the effect of orthorhombicity is eliminated. These results provide thermodynamic evidence that the pseudogap onset is associated with a second-order nematic phase transition, which differs from the recently reported charge-density-wave transition that accompanies translational symmetry breaking2,3,4,5,6,7,8,9,10.

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Figure 1: In-plane torque magnetometry in YBCO single crystals.
Figure 2: In-plane anisotropy of the magnetic susceptibility for underdoped YBCO with different hole doping levels.
Figure 3: Temperature-doping phase diagram of YBCO.
Figure 4: Induced nematicity and the scaling behaviour.


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We thank A. Carrington, R. M. Fernandes, T. Hanaguri, N. Harrison, S. M. Hayden, M.-H. Julien, S. Kivelson, H. Kontani, C. Putzke, T. M. Rice, S. Sachdev, L. Taillefer, T. Tohyama, H. Yamase and J. Zaanen for fruitful discussions, and M. Ishikawa and H. Yamochi for experimental support. This work was supported by Grants-in-Aid for Scientific Research (KAKENHI) (Nos. 25220710, 15H02106, 15H03688, 16K05460, 16K13837) and on Innovative Areas ‘Topological Material Science’ (No. 15H05852) from Japan Society for the Promotion of Science (JSPS). The characterization of YBCO single crystals was partly performed at Advanced Instruments Center at Kyushu Sangyo University. E.-G.M. acknowledges the financial supports from the POSCO Science Fellowship of POSCO TJ Park Foundation and NRF of Korea under Grant No. 2017R1C1B2009176.

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T.N., T.L., J.P. and B.K. prepared the high-quality single-crystalline samples. Y.S., H.M. and S.K. performed the magnetic torque measurements. Y.S., S.K., E.-G.M. and Y.M. analysed the data. S.K., E.-G.M., Y.K., T.S., B.K. and Y.M. discussed and interpreted the results and prepared the manuscript.

Correspondence to Y. Matsuda.

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Sato, Y., Kasahara, S., Murayama, H. et al. Thermodynamic evidence for a nematic phase transition at the onset of the pseudogap in YBa2Cu3Oy. Nature Phys 13, 1074–1078 (2017).

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