Kondo Effect in Nonreciprocal Response

Abstract

Chiral magnetic states give rise to rich phenomena, from the anomalous Hall effect and the nonlinear electrical current to multiferroics and magnetochiral dichroism. Most of the studies on electrical transport so far have focused on the cases where the magnetic moments are well approximated by classical local moments. Here, we reveal that the coexistence of quantum fluctuations and chiral spin correlations gives rise to a $\log(T)$ temperature dependence in the electrical magnetochiral effect, a nonreciprocal response. Using the Green's function method and a scattering theory approach, we show that the $\log(T)$ temperature dependence occurs through a scattering process similar to that of the Kondo effect. The electrical magnetochiral effect is sensitive to the sign of vector spin chirality and the magnetic field. The results demonstrate that local spin correlations and quantum fluctuations cooperatively induce nontrivial properties in transport phenomena.

Figures (3)

• Figure 1: Schematics of the asymmetric magnetic scattering by two spins with non-zero vector spin chirality. The scattering rate for backscattering depends on the direction of the incoming electron and the vector spin chirality, resulting in a nonreciprocal current.
• Figure 2: Temperature dependence of nonreciprocal conductivity $\sigma^{(2)}_{zzz}$. The blue lines represent the leading-order contribution, which is proportional to the product of magnetization and vector spin chirality, $m\chi^z$. The orange lines are ones with quantum Kondo-type corrections $2J\rho\log(T/\Lambda)$. The symbols connected by lines are calculated by Onsager's reaction field theory (ORF) with classical spins, while the bold solid lines are calculated by the high-temperature expansion with quantum spins. The results are for $d/j=0.2$, $h/j=0.002$, $T_K/j=2$, $J\rho=-0.15$, $S=1/2$ where $T_K=\Lambda\exp(1/J\rho)$ is the Kondo temperature.
• Figure 3: Oscillatory behavior of the dimensionless functions $f_1$ and $f_2$. (a) The functions plotted against the dimensionless distance $x=k_F R$. The solid blue line shows the full function $f_2$, which is composed of a logarithmic part (dashed orange line) and a temperature-independent part (dotted green line). The solid gray line shows the function $f_1$ scaled by a factor $C=6(\Lambda/\mu)[-\log(T/\Lambda)]$ for comparison with the logarithmic part of $f_2$, highlighting their similar oscillatory forms. (b) The same functions plotted with respect to the band filling $\nu$. Line styles and colors are the same as in panel (a). Parameters used for the plots are $\Lambda=4$ and $T=0.01$, with a chemical potential given by $\mu = 2^{1/3}\nu^{2/3}$. Panel (a) is plotted at a fixed filling of $\nu=2$, while panel (b) uses a fixed nearest-neighbor distance $R=a$.