Evidence Accumulates for Unusual Behavior in Underdoped High‐ $T_{c}$ Superconductors

JUN 01, 1996

The energy gap that conventionally heralds the onset of a superconducting state has been seen in materials well above the temperatures at which they actually become superconducting.

DOI: 10.1063/1.2807647

Barbara Goss Levi

As you cool a conventional superconductor, it acts as a metal until it reaches the critical temperature $T_{c},$ below which it rapidly goes superconducting. But some of the high‐temperature, copper oxide materials—in particular, the underdoped ones, whose densities of charge carriers are below that which gives the highest $T_{c}$ —seem to be preparing for the transition to a superconducting state well before they reach $T_{c} .$ Experiment after experiment on underdoped materials at temperatures above $T_{c}$ has revealed some kind of crossover or change in behavior, which some feel is related to the eventual onset of superconductivity at lower temperatures. When the temperature does reach $T_{c},$ the material goes superconducting, but some of its properties exhibit relatively little additional discontinuity in behavior.

Evidence Accumulates for Unusual Behavior in Underdoped High‐Tc Superconductors

Evidence Accumulates for Unusual Behavior in Underdoped High‐ $T_{c}$ Superconductors