Locating the pseudogap closing point in cuprate superconductors: Absence of entrant or reentrant behavior
Abstract
Many current descriptions of the pseudogap in underdoped cuprates envision a doping-dependent transition line T*(p ) which descends monotonically toward zero just beyond optimal doping. There is much debate as to the location of the terminal point p* where T*(p ) vanishes, whether or not there is a phase transition at T* and exactly how T*(p ) behaves below Tc within the superconducting dome. One perspective sees T*(p ) cutting the dome and continuing to descend monotonically to zero at p*≈0.19 holes/Cu—referred to here as entrant behavior. Another perspective derived from photoemission studies is that T*(p ) intersects the dome near p ≈0.23 holes/Cu then turns back below Tc, falling to zero again around p*≈0.19 —referred to here as reentrant behavior. By examining field-dependent thermodynamic data for Bi2Sr2CaCu2O8 +δ we show that neither entrant nor reentrant behavior is supported. Rather, p* sharply delimits the pseudogap regime: For p <0.19 the pseudogap is always present, independent of T . Similar results are found for Y0.8Ca0.2Ba2Cu3O7 -δ . For both materials, T*(p ) is not a temperature but a crossover scale, ≈E*(p ) /2 kB , reflecting instead the underlying pseudogap energy E*(p ) which vanishes as p →p*≈0.19 .
- Publication:
-
Physical Review B
- Pub Date:
- May 2020
- DOI:
- 10.1103/PhysRevB.101.174512
- arXiv:
- arXiv:1907.12018
- Bibcode:
- 2020PhRvB.101q4512T
- Keywords:
-
- Condensed Matter - Superconductivity;
- Condensed Matter - Strongly Correlated Electrons
- E-Print:
- 20 Pages, 9 Figures, in press Phys. Rev. B