Magnetic susceptibility of the doped Mott insulator: Gauge theory

We discuss the orbital part of the magnetic susceptibility ${\mathrm{\chi }}_{\mathit{d}}$ of the doped Mott insulator in two dimensions. Starting from the U(1) gauge theory, we obtain corrections to ${\mathrm{\chi }}_{\mathit{d}}$ due to gauge-field fluctuations. We find that these fluctuations reduce the Bose contribution to the susceptibility, implying that the Bose-condensation temperature is strongly suppressed by gauge interactions. The temperature dependence of ${\mathrm{\chi }}_{\mathit{d}}$ is obtained by a numerical simulation of a lattice Bose gas interacting with a random magnetic field, and found to be consistent with recent data on high-${\mathit{T}}_{\mathit{c}}$ oxides.