Pseudogap temperature dependence

Abstract Existing data on 63Cu-nuclear spin relaxation reveal two independent relaxation processes the one that is temperature independent we link to incommensurate peaks seen by neutrons, while the "universal temperature dependent contribution coincides with 1/6371 (1/ ) for two-chain YBCO 124. We argue that this new result substitutes for a "pseudogap regime in a broad class of high-Tc cuprates and stems from the 1st order phase transition that starts well above the superconductivity Tc but becomes frustrated because of broken electroneutrality in the CuC>2 plane. 

Figure 3. T-dependence of (205,I T) (a) and of 205 /if1 (b) at low temperatures. The filled and open circles represent the data at vortex cores and at the saddle point, respectively. T 120 K is the pseudogap temperature. The dotted line represents the Curie-Weiss law which is determined above T. In (b), TN is the temperature at which 205/if1 at the core exhibits a sharp peak.

Figure 2. (a)The subtracted TEP (AS = S(T) - SpT)) data with linear fitting function Sl(T) = aT+f) for typical LSCO samples. The inset shows the doping dependence of the slope (a) and the offset (J3) for SL(T). (b) Characteristic temperatures, Tc, Th, Tj and Tp (See the text.) with the pseudogap temperatures reported from various experiments for LSCO (Ref. [1]). 

Figure 1. Temperature dependence of the resistivity of (a) a polycrystalline sample of the underdoped cuprate Lai.gSro.iCuC>4, taken from [1], and (b) a film of the same composition and thickness 150 nm, taken from [2]. In (b), the measurements correspond to the in-plane direction (parallel to the CuC>2 layers). The temperatures T, Tc and l c correspond, respectively, to the pseudogap opening temperature, to the temperature where the SCF effects become indistinguishable, and to the (inflexion-point) observed normal-superconducting transition temperature.

At sufficiently high temperatures KCP falls into the cross-over limit. f 0J, measured1 , or calculated from Equ. (22), is considerably smaller than d . However, I ox itself is (non-critically) temperature dependent and at Tc is estimated to be of of the order of d . However, the temperature dependence given by Equ. (22) (and also by Equs. (19, 20)) should not be taken too seriously for T < rMF. This equation neglects (at least) the electron-self-energy effects13 2 2-2 3) (the Peierls pseudogap). Still, it appears probable that close to Tc, KCP falls somewhere between the two extreme limits considered here. 

The first evidence for a pseudogap in the Raman scattering response of the cuprates was actually inferred from the anomalous temperature dependences of Raman- and infrared-active phonons (Litvinchuk et al. 1992). More recently, evidence for a pseudogap has... 

It is interesting to compare the effect of pressme with that of uniaxial pressure. Unlike under uniaxial pressure, CeNiSn exhibits a transition from a pseudogapped state to a magnetically ordered state for P//b-axis and P//c-axis, while no transition occurs imder P//a-axis. The magnetic susceptibility x at various uniaxial pressures is shown in Figure 131. At ambient pressure, the temperature dependence of the susceptibility... 

The independence of the SCF and the pseudogap seems to be confirmed when three characteristic temperatures, Tc, Tc and T, are compared. This is done in Fig. 3, where the doping dependence of Tc, Tc and 7 is represented. The data for T where taken from Ref. [9], This figure illustrates that in the underdoped La. Sr.CuCL superconductors not only Tc but also T° is much lower than T and that the doping behaviour of both Tc and T° is very different from the one of T. ... 

Pseudogap behavior is most easily identified at temperatures below T but well above the superconducting transition temperature. A simple expression for the doping dependence of T for the 2-1-4 materials that is consistent with the Nakano analysis and the Matsuda experiments is... 

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