ONE-DIMENSIONAL ELECTRON-SYSTEM WITH ATTRACTIVE INTERACTION IN A MAGNETIC-FIELD

The phase transition with respect to a magnetic field from a nonmagnetic (h < Δ) to a paramagnetic (h > Δ) state at zero temperature in a one-dimensional electron system with attractive interaction is studied. An exact solution of the Luther-Emery model for a particular value of the coupling constant U{norm of matrix}=-6πVF/5 is used. The transition shows up as the appearance of a gapless mode in the spin-excitation spectrum at the critical field hc=Δ, where Δ is the gap in the spectrum in zero field. The behavior of various correlation functions and the low-temperature anomalies of the thermodynamic quantities are calculated. Some questions related to a quantitative description of the transition in the Luther-Emery model for U{norm of matrix}≠-6πVF/5, and also in other models, are discussed. © 1979 Plenum Publishing Corporation.