Strings and stripes in ionic solids

We demonstrate the existence of strings or electronic molecules in narrow band ionic insulators arising purely from the Fröhlich electron–phonon interaction alone. The system is in an inhomogeneous state in a wide range of physically interesting parameters, where the electronic molecules may coexist with the Fermi liquid. We show that conditions for string existence, the string length and the number of self-trapped particles depend on the electron(hole) conduction bandwidth and on the ratio of high frequency and static dielectric constants.