Pressure dependence of out-of-plane conduction inLa2−xSr

Abstract

Pressure dependence of out-of-plane resistivity c has been investigated in an optimally-doped high-T c cuprate La 2Ϫx Sr x CuO 4 . By applying pressure, we found a drastic decrease in c which reaches 50% at Pϭ8 GPa. This surprisingly large P dependence implies that the thermal contraction along the c axis is significantly reflected in the c (T) curve, leading to a metal-like term; hence La 2Ϫx Sr x CuO 4 is essentially characterized as a two-dimensional metal modified with nonmetallic conduction between CuO 2 layers. Tunneling is suggested for a possible mechanism for c .

c-axis transport and resistivity anisotropy of lightly to moderately dopedLa2−xSrKomiya1, Ando2, Sun3 et al. 2002Phys. Rev. B1026560View full textAdd to dashboardCite

“…Figure 3 shows the temperature dependence of ρ c for the same doping range. In the ρ c (T ) profile of LSCO, a clear kink is usually observed at the structural phase transition temperature from the high-temperature tetragonal (HTT) phase to the low-temperature orthorhombic (LTO) phase 2, 22,24,28 ; for all the compositions of the present study, however, the structural phase transition occurs at temperatures higher than 300 K (Ref. 37), except for the x=0.10 sample which show the LTO transition at 293 K. We note that the data for x=0.01 show a kink at 240 K, which corresponds to the Néel temperature T N and not to the LTO transition temperature.…”

“…26,27 This is partly because large single crystals can be grown with the travelingsolvent floating-zone (TSFZ) technique for LSCO and thus it is easy to obtain samples that are long enough along the c-axis to allow reliable c-axis transport measurements. It has been demonstrated 2 that ρ c (T ) in slightly underdoped samples (0.10 < x < 0.16) shows only a weak temperature dependence at moderate temperatures (100 − 300 K), particularly after correcting for the thermal expansion, 22 which is in contrast to the behaviors of ρ c (T ) of Bi-2212 or Bi-2201, 15,16,17 where the pseudogap causes ρ c (T ) to become steeply insulating. The magnetoresistance study by Hussey et al 24 has shown that the c-axis transport of LSCO is incoherent and ρ c is governed in a large part by the in-plane scattering rate.…”

Normal-State c-Axis Resistivity of the High-Tc Cuprate Superconductors

“…We would now like to comment on a recent attempt to explain away the metallicitiy of ρ c (T ) as a thermal expansion effect. 20 Based on a recent study of the pressure dependence of ρ c (T ) and the lattice constant 'c' in La 2−x Sr x CuO 4 , it has been argued that the observed metallicity (i.e., TCR > 0) merely reflects a thermal expansion effect, i.e.,…”

Highly anisotropic layered systems: intraplanar metallicity and inter–planar non–metallicity

“…Also, the possible connection of this upturn to the opening up of an energy gap as a precursor to T c is not ruled out (Zha 1996;Balestrino et al 1993). Moreover, as has been pointed out by Nakamura et al (1996), the metallicity of ρ c (T ) may only be 'apparent', arising from the c-axis thermal expansion effects. Besides, in many, mostly underdoped, samples, ρ c (T ) seems semiconducting over the entire temperature range (Ong 1994;Kimura et al 1996).…”