From charge- and spin-ordering to superconductivity in the organic charge-transfer solids

摘要: We review recent progress in understanding the different spatial broken symmetries that occur normal states of family charge-transfer solids (CTS) exhibit superconductivity (SC), and discuss how this knowledge gives insight to mechanism unconventional SC these systems. show a unified theory diverse symmetry necessarily requires explicit incorporation strong electron-electron interactions lattice discreteness, most importantly, correct bandfilling one-quarter. Uniquely quarter-filled band, there is very tendency form nearest neighbor spin-singlets, both one two dimensions. The quantum effect, drives commensurate charge-order correlated band. This charge-ordered spin-singlet, which we label as paired-electron crystal (PEC), from competes with antiferromagnetic state Wigner single electrons. Further, unlike classical symmetries, PEC characterized by spin gap. dimensions enhanced frustration. Following characterization critically reexamine spin-fluctuation resonating valence bond theories frustration-driven within half-filled band Hubbard Hubbard-Heisenberg Hamiltonians for superconducting CTS. develop valence-bond reached destabilization additional pressure-induced frustration makes spin-singlets mobile. Our proposed same CTS proximate semiconducting instead charge-ordered, only difference former generated via fluctuating spin-singlet opposed static PEC.