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The existence of novel inhomogeneous and/or anisotropic quantum ground
states in various electronic systems have been demonstrated by
remarkable experiments on a number of different systems, in the last few
years. I will review the phenomena of inhomogeneous spin and charge ordering observed in some of complex materials such as high temperature
superconductors, and manganite. I will show a microscopic theory of the electronic nematic Fermi liquid where the system of interacting fermions spontaneously breaks the rotational symmetry while the translational symmetry is
preserved. A consequence of the nematic order in the context of the sound
propagation and the pairing instability in the nematic state will be presented. I will also discuss the breakdown of the Fermi liquid theory in these types of ground states, and the theoretical studies to understand the underlying mechanism of exotic orderings and their electronic properties. |