Flexuron: A self-trapped state of electron in crystalline membranes

Self-trapping of an electron due to its interaction with bending fluctuations in a flexible crystalline membrane is considered. Due to the dependence of the electron energy on the corrugations of the membrane, the electron can create around itself an anomalously flat (or anomalously corrugated, depending on the sign of the interaction constant)region and be confined there. Using the Feynman path integral approach, the autolocalization energy and the size of the self-trapped state (flexuron) are estimated. It is shown that typically the size of the flexuron is of the order of the wavelength of fluctuations at the border between harmonic and anharmonic regimes. The flexuron states are connected with the fluctuation tail of the electron density of states, the asymptotic behavior of this tail being determined by the exponent of the renormalized bending rigidity.