文摘
We show that at certain conditions electronic molecules may arise in solids with narrow bands. The behaviour of the electronic (e-)molecules is very quantum, their shapes and sizes are not well defined while varying in some limits. In narrow band ionic insulators, they may form strings or stripes which may arise due to Fröhlich electron-phonon interaction alone. In underdoped antiferromagnet (AF) the e-molecule consists of a few holes segregated around a rectangular or a square loop which is created from anti-phase domain wall, ie the string has here a form of a loop. If it is an insulating state then the system consists of such isolating clusters. If it is a metallic state the system is in an inhomogeneous state consisting of a liquid of e-molecules embedded into Fermi see. The conditions for the linear or loop string existence and formation, the size, the shape and the number of particles self-trapped into depend on the electron(hole) conduction bandwidth and on the ratio of high frequency and static dielectric constants as well as on the value of the antiferromagnetic coupling J. An inhomogeneous state with e-molecules may arise in a wide range of physically interesting parameters and we show that such inhomogeneous insulating and conducting states with e-molecules relevant to oxide materials, like HTSC.