Spin response of a charge-density wave

Abstract

The broken translational symmetry of a charge-density wave (CDW) leads to a new collective mechanism of spin response which supplements the usual Pauli ($q$-dependent) paramagnetism. This phenomenon, absent in a homogeneous electron gas, cannot be described within a perturbative approach. If the wave vector $\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}$ of a "staggered" magnetic field is close to the CDW wave vector $\stackrel{\ensuremath{\rightarrow}}{\mathrm{Q}}$, the densities of spin-up and spin-down electrons acquire long-wavelength phase modulations of opposite sign. The spin response has two components: one at $\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}$, the applied periodicity, and the other at $2\stackrel{\ensuremath{\rightarrow}}{\mathrm{Q}}\ensuremath{-}\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}$. Both response components exhibit a sharp peak when $\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}$ is near $\stackrel{\ensuremath{\rightarrow}}{\mathrm{Q}}$, which leads to a very-long-range, indirect-exchange interaction between nuclear spins.