Calorimetric determination of the magnetic phase diagram of underdoped ortho II YBa2Cu3O6.54 single crystals

• Published in: Nature communications 2015-08, Vol.6 (1), p.7927-7927, Article 7927
• Main Authors: Marcenat, C., Demuer, A., Beauvois, K., Michon, B., Grockowiak, A., Liang, R., Hardy, W., Bonn, D. A., Klein, T.
• Format: Article
• Language: English
• Subjects: 639/301/119/1003; 639/301/119/2795; Constraint modelling; Critical field (superconductivity); Dependence; Fermi surfaces; Heat; Heat measurement; High temperature superconductors; Humanities and Social Sciences; Magnetic fields; multidisciplinary; Phase diagrams; Phase transitions; Physics; Science; Science (multidisciplinary); Single crystals; Superconductivity
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms8927

The recent discovery of a charge order in underdoped YBa 2 Cu 3 O y raised the question of the interplay between superconductivity and this competing phase. Understanding the normal state of high-temperature superconductors is now an essential step towards the description of the pairing mechanism in those materials and determining the upper critical field is therefore of fundamental importance. We present here a calorimetric determination of the field–temperature phase diagram in underdoped YBa 2 Cu 3 O y single crystals. We show that the specific heat saturates in high magnetic fields. This saturation is consistent with a normal state without any significant superconducting contribution and a total Sommerfeld coefficient γ N ∼6.5±1.5 mJ mol −1  K −2 putting strong constraints on the theoretical models for the Fermi surface reconstruction. The presence of a charge order state in underdoped YBCO raises the question of the interplay between this phase and the superconducting one. Here, the authors characterize this material’s phase diagram through specific heat and magnetic measurements, providing strong constrains to theoretical models.