Abstract
Until the mid-1980s, condensed matter physicists were contented with the nearly independent electron model or quasiparticle picture developed out of weakly interacting Fermions. Discoveries of high Tc superconductivity in oxides and other exotic systems, namely heavy Fermion systems, colossal magnetoresistive manganites, metal-insulator transition in two dimensions etc presented a variety of formidable challenges to work within the conventional ideas. Soon it became clear that there is a need to develop microscopic theories of correlated electron systems. There one has to take into account explicit inter-electron Coulomb interactions to understand several remarkable properties of these novel materials. Since last two decades the 'correlated electron systems' remain at the forefront of condensed matter physics. Experimental techniques and fine measurements (angle-resolved photoemission, optical, tunnelling and neutron scattering studies etc.) are far ahead of the theory. Mathematical formalism dwells a lot on the field theoretical techniques. Numerical simulation is undergoing rapid advancement. Charge and spin degrees of electrons, phonons and their interaction with electrons contribute non-trivially to the exotic properties. If we consider the example of high Tc oxides, we start with the parent undoped material as a highly correlated antiferromagnetic Mott insulator. Under hole/electron doping, the system becomes a superconductor with d-wave pairing. Here we encounter several phase changes as doping continues. In particular, the understanding of the normal state (above the superconducting phase) poses enormous difficulties in terms of their anomalous properties. Now a large number of researchers are working on various important aspects of this unresolved issue. However, there is no clear consensus. As well as posing the deepest intellectual challenges on fundamentals, these materials offer new possibilities for technological applications. This special issue presents invited articles from some of the leading exponents of this fascinating field of research.
Original language | English |
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Pages (from-to) | 120302 |
Journal | Journal of Physics: Condensed Matter |
Volume | 19 |
Issue number | 12 |
DOIs | |
Publication status | Published - 2007 |