We study a magnetic impurity placed in the two-dimensional antiferromagnetic quantum critical metal (AFQCM), using the field-theoretic functional renormalization group. Critical spin fluctuations represented by a bosonic field compete with itinerant electrons to couple with the impurity through the spin-spin interaction. At long distances, the antiferromagnetic electron-impurity (Kondo) coupling dominates over the boson-impurity coupling. However, the Kondo screening is weakened by the boson with increasing severity as the hot spots connected by the magnetic ordering wave vector are better nested. For $v_{0,i}\ll 1$, where $v_{0,i}$ is the bare nesting angle at the hot spots, the temperature $T_K^{\mathrm{AFQCM}}$ below which Kondo coupling becomes $O\left(1\right)$ is suppressed as $\frac{log\mathrm{\Lambda }/T_K^{\mathrm{AFQCM}}}{log\mathrm{\Lambda }/T_K^{\mathrm{FL}}}\sim \frac{g_{f,i}}{v_{0,i}log1/v_{0,i}}$, where $T_K^{\mathrm{FL}}$ is the Kondo temperature of the Fermi liquid with the same electronic density of states, and $g_{f,i}$ is the boson-impurity coupling defined at UV cutoff energy $\mathrm{\Lambda }$. The remarkable efficiency of the single collective field in hampering the screening of the impurity spin by the Fermi surface originates from ultraviolet/infrared (UV/IR) mixing: bosons with momenta up to a UV cutoff actively suppress Kondo screening at low energies.

Close

PrevNext

View figure in article

• Kondo effect
• Quantum criticality
• Spin fluctuations
• Strongly correlated systems