Abstract
We have investigated the effect of pressure on the electrical transport and the structural properties of . The temperature dependence of the electrical resistivity up to shows no indication of an insulator-to-metal transition. However, the analysis of the pressure dependence of the energy gap around reveals first a strong decrease of with increasing pressure, followed by a much weaker decrease of above , indicating a change of the electronic structure. The analysis of the pressure dependence of the lattice parameters up to reveals an extreme anisotropic and anomalous change of the lattice parameters with increasing pressure. While the lattice parameters and smoothly decrease up to the highest pressure, the lattice parameter remains nearly pressure independent above about . It is shown that such anomalous change of the lattice parameters with pressure strongly affects the relative strength of the effective direct and indirect hopping along the and axis, respectively, and therefore it is responsible for the observed pressure-induced change of the electronic properties of above .
2 More- Received 18 January 2008
DOI:https://doi.org/10.1103/PhysRevB.77.165121
©2008 American Physical Society