The underdoped-overdoped transition in YBa2Cu3Ox
نویسنده
چکیده
The overdoped regime of YBa2Cu3Ox is accessible with heavy oxygen dopings close to x = 7. The crossover from the underdoped to the overdoped regimes occurs around xopt = 6.92, nearly coinciding with a displacive structural phase transition [1]. It is suggesting to associate the structural instability close to optimum doping with a kind of barrier limiting Tc. The 123 bi-layer cuprates exhibit comparatively low “optimum”Tc‘s around 90 K, but chemical trends and pressure experiments imply that Tc is not yet at its optimum value. In this communication we discuss a mechanism being possibly responsible for the barrier limiting Tc of YBa2Cu3Ox, and stabilizing the overdoped regime for x ≥ 6.95.
منابع مشابه
The dimpling in the CuO2 planes of YBa2Cu3Ox (x=6.806-6.984, T=20-300 K) measured by yttrium EXAFS
The dimpling of the CuO2 planes (spacing between the O2,3 and Cu2 layers) in YBa2Cu3Ox has been measured as a function of oxygen concentration and temperature by yttrium x-ray extended-fine-structure spectroscopy (EXAFS). The relative variations of the dimpling with doping (x = 6.806 − 6.984) and temperature (20300 K) are weak (within 0.05 Å), and arise mainly from displacements of the Cu2 atom...
متن کاملLOCAL STRUCTURE STUDIES OF THE UNDERDOPED-OVERDOPED TRANSITION IN YBa2Cu3Ox Measurement of the yttrium x-ray absorption-fine-structure
We have measured the extended x-ray absorption-fine-structure (EXAFS) at the Y-K edge of YBa2Cu3Ox for x=6.801, 6.947, 6.968, 6.984 at T=20-300 K. The Y–Cu2 pairs vibrate harmonically but freeze out in the superconducting phase. The Y-O2,3 pairs exhibit strong anharmonicities with a singularity at Tc. With increasing oxygen concentration the Cu2 layer shifts along c towards the Ba layer. Optimu...
متن کاملOn the origin of the double superconducting transition in overdoped YBa2Cu3Ox
The superconducting transition in a single overdoped, detwinned YBa2Cu3Ox (YBCO) crystal is studied using four different probes. Whereas the AC and DC magnetic susceptibilities find a dominant transition at 88 K with a smaller effect near 92 K, the specific heat and electrical resistivity reveal only a single transition at 88 K and 92 K, respectively. Under hydrostatic pressures to 0.60 GPa the...
متن کاملWhat Can We Learn from Comparison between Cuprates and He Films ? : Phase Separation and Fluctuating Superfluidity
In the underdoped, overdoped, Zn-doped or stripe-forming regions of high-Tc cuprate superconductors (HTSC), the superfluid density ns/m∗ at T → 0 shows universal correlations with Tc. Similar strong correlations exist between 2dimensional superfluid density and superfluid transition temperature in thin films of He in non-porous or porous media, and He/He film adsorbed on porous media. Based on ...
متن کاملFrom underdoped to overdoped cuprates: two quantum phase transitions.
Several experimental and theoretical studies indicate the existence of a critical point separating the underdoped and overdoped regions of the high-T(c) cuprates' phase diagram. There are at least two distinct proposals on the critical concentration and its physical origin. The first one is associated with the pseudogap formation for p < p, with p≈0.2. The other relies on the Hall effect measur...
متن کامل