Theory Seminar: *Kondo impurity in attractive Hubbard bath*

Zhi-Yuan Wei (MPQ): In this work, we theoretically study the ground-state properties and out-of-equilibrium dynamics when a Kondo impurity couples with 1D and 2D attractive Hubbard bath at half-filling. 

Zhi-Yuan Wei (MPQ)
Group seminar (hybrid format: B0.32/zoom)
Wed, 25 May 2022, 10:30 am (MEZ)

Abstract:

In this work, we theoretically study the ground-state properties and out-of-equilibrium dynamics when a Kondo impurity couples with 1D and 2D attractive Hubbard bath at half-filling. First, we find the ground state exhibits a singlet-doublet phase transition, and observe the competition between the Kondo correlation and the superconducting (SC) order. In particular, the SC gap on the two sides of the 1D chain exhibit a \pi phase shift when the Kondo singlet forms.

Then we study the relaxation dynamics of the impurity coupled to a 2D bath, and observe a fast buildup of Kondo correlation near the impurity, with a spin-wave emitted into the bath. The presence of the SC gap leads to an exponential decay of the spin-wave amplitude, and the spin-wave, in turn, suppresses the local SC gap dynamically.

Finally, we study the transport between two 1D chains connected by the impurity. By adding a bias voltage, we observe the Josephson effect in the weak-link regime and the ballistic charge transport when the Kondo singlet forms. The charge transport further dramatically influences the bath and the impurity state, leading to rich behaviors such as the dynamical transition of the SC ordering to the charge-density-wave (CDW) ordering and the dynamical breaking of the Kondo singlet.

Overall, our results provide a comprehensive understanding of the Kondo impurity coupled with an attractive Hubbard bath, and potentially serve as a theoretical foundation for quantum simulation of superconductor-quantum dot devices.

If you’d like to participate in the seminar, please contact us!