Core Concepts
The upper critical field Hc2(0) of high-Tc cuprate Bi2+xSr2-xCaCu2O8+d increases monotonically with hole doping from the underdoped to the overdoped regime, in contrast to the parabolic doping dependence of the critical temperature Tc.
Abstract
The authors investigated the temperature (T) dependence of the irreversibility field Hirr(T) in high-critical-temperature cuprate Bi2+xSr2-xCa1-yYyCu2O8+δ (Bi-2212) single crystals over a wide range of hole doping level (p). Hirr(T) was evaluated by measuring the magnetization hysteresis loop. The value of Hirr(T) extrapolated to T = 0 K [Hirr(0)], is either equal to or sets the lower boundary for the upper critical field at T = 0 K [Hc2(0)].
The key findings are:
- Tc shows a parabolic p-dependence with a peak at p = 0.16.
- 0Hirr(0) increases monotonically with p by approximately one order of magnitude, from 19 T for the most underdoped sample (p = 0.065, Tc = 24 K) to 209 T for the most overdoped sample (p = 0.200, Tc = 75 K).
- The observed p-dependence of Hirr(0) in Bi-2212 is distinct from those in YBa2Cu3O7-δ and HgBa2CuO6+δ, in which a pronounced dip structure appears in the underdoped region. This suggests that the influence of the competing order in Bi-2212 is less prominent than that in the other two systems.
- The present results qualitatively agree with Hc2(0) values evaluated from the specific heat measurements, but are higher than those estimated from the Nernst effect measurements.
Stats
Tc = 24 K for the most underdoped sample (p = 0.065)
Tc = 75 K for the most overdoped sample (p = 0.200)
0Hirr(0) = 19 T for the most underdoped sample (p = 0.065)
0Hirr(0) = 209 T for the most overdoped sample (p = 0.200)
Quotes
"Tc shows a parabolic p-dependence (peak at p = 0.16), whereas 0Hirr(0) increases monotonically with p by approximately one order of magnitude, from 19 T for the most underdoped sample (p = 0.065, Tc = 24 K) to 209 T for the most overdoped sample (p = 0.200, Tc = 75 K)."
"The observed p-dependence of Hirr(0) in Bi-2212 is distinct from those in YBa2Cu3O7-δ and HgBa2CuO6+δ, in which a pronounced dip structure appears in the underdoped region."