title: Calorimetric determination of the magnetic phase diagram of underdoped ortho II YBa2Cu3O6.54 single crystals.
abstract: The recent discovery of a charge order in underdoped YBa2Cu3Oy 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 YBa2Cu3Oy 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 γN∼6.5±1.5 mJ mol(-1) K(-2) putting strong constraints on the theoretical models for the Fermi surface reconstruction.
authors: Université Grenoble Alpes, INAC-SPSMS, F-38000 Grenoble, France.|CEA, INAC-SPSMS, F-38000 Grenoble, France.
authors: C
authors: C
authors: Marcenat
authors: Université Grenoble Alpes, LNCMI, F-38042 Grenoble, France.|CNRS, LNCMI, F-38042 Grenoble, France.
authors: A
authors: A
authors: Demuer
authors: Université Grenoble Alpes, Institut NEEL, F-38042 Grenoble, France.|CNRS, Institut NEEL, F-38042 Grenoble, France.
authors: K
authors: K
authors: Beauvois
authors: Université Grenoble Alpes, Institut NEEL, F-38042 Grenoble, France.|CNRS, Institut NEEL, F-38042 Grenoble, France.
authors: B
authors: B
authors: Michon
authors: National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA.
authors: A
authors: A
authors: Grockowiak
authors: Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1.|Canadian Institute for Advanced Research, Toronto, Ontario, Canada M5G 1Z8.
authors: R
authors: R
authors: Liang
authors: Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1.|Canadian Institute for Advanced Research, Toronto, Ontario, Canada M5G 1Z8.
authors: W
authors: W
authors: Hardy
authors: Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1.|Canadian Institute for Advanced Research, Toronto, Ontario, Canada M5G 1Z8.
authors: D A
authors: DA
authors: Bonn
authors: Université Grenoble Alpes, Institut NEEL, F-38042 Grenoble, France.|CNRS, Institut NEEL, F-38042 Grenoble, France.
authors: T
authors: T
authors: Klein