Non-Hermiticity Induced Universal Anomalies in Kondo Conductance

Abstract

Strong correlation, when combined with dissipation in open systems, can lead to a variety of exotic quantum phenomena. Here, we study nontrivial interplays between non-Fermi liquid behaviors emerging from strong correlation and non-Hermiticity arising from open systems. We propose a practical physical setup that realizes a non-Hermitian multichannel Kondo model. We identify a weak-coupling local moment fixed point and a strong-coupling non-Fermi liquid fixed point under PT symmetry, both are enriched by the non-Hermitian effect. Remarkably, universal unconventional Kondo conductance behaviors are found for both cases, which are distinct from all previously studied Kondo systems. Particularly, we show that an anomalous upturn of conductance could take place with increasing the temperature, originating from the interplay between non-Fermi liquid and non-Hermiticity. Our results identify a novel class of transport phenomena unrecognized before, driven by intertwined effects of correlation and dissipation.

Figures (4)

• Figure 1: Schematic plot of the two FPs of the nHMCK model revealed by the renormalization group flow. The blue and red dot represent the weak- and strong-coupling FP, respectively. Around both FPs, novel Kondo conductance emerges due to the non-Hermitian effect arising from the dissipation into the environment.
• Figure 2: The junction setup that realizes the non-Hermitian Majorana tunneling. (a) Majorana edge mode (red dot) tunnels into the normal lead with the assistance of a QD, which is in turn coupled to an environment. (b) The detailed structure of the QD-environment system, which is attached to a feedback-resetting setup.
• Figure 3: (a) The multi-junction structure that realizes the nHMCK model. The $M=3$ case is shown as an example. (b) The RG flow in the complex plane. The yellow curve denotes the critical points separating the weak- and strong-coupling phase. (c) shows the zoom-in RG flow around the weak-coupling FP, which indicates universal scalings of the Kondo coupling $g_r$ and $g_i$. (d)-(f) The NRG results of the general non-Hermitian Kondo model for $n=2$. (d) shows the impurity entropy versus temperature with varying $\theta$, and (e), (f) are the energy spectrum for the weak ($\theta=0.1$) and strong non-Hermiticity ($\theta=1.0$) case, respectively. Both the real and imaginary spectrum are plotted, which are compared to the Hermitian case (black curves).
• Figure 4: (a) and (b) show the NRG results of the real and imaginary energy spectrum for the $\mathcal{PT}$ symmetric nHMCK model. The spectrum is shown for the weak (a) and strong (b) non-Hermiticity case, respectively. The obtained energy levels and degeneracies exactly coincide with those predicted by BCFT (highlighted by arrows in (b)). (c) The conductance of the nHMCK ($n=4$). The red and blue solid curves correspond to the strong- and weak-coupling phases, respectively. The red dashed curve shows the strong-coupling conductance for the Hermitian 4-channel Kondo model. The blue dashed-dot curve is the conductance in the unscreened channel of an anisotropic multichannel Kondo model PhysRevB.83.245308, which is shown for the purpose of comparison. The inset depicts the measurement setup.