Non-Fermi-liquid behavior in transport through Co-doped Au chains

Area of Science:

• Condensed Matter Physics
• Quantum Mechanics
• Materials Science

Background:

• Understanding electron transport in nanoscale magnetic systems is crucial for spintronics.
• Magnetic impurities in atomic chains exhibit complex quantum phenomena.

Purpose of the Study:

• To investigate the low-temperature conductance of monatomic gold chains with a single cobalt (Co) magnetic impurity.
• To explore the transition from Kondo physics to other quantum phases by altering chain length.

Main Methods:

• Ab initio calculations to inform an effective model.
• Construction of an effective Hamiltonian (Ĥ(eff)) describing Co 3d electron hybridization with Au 5d electrons.
• Numerical Renormalization Group (NRG) to solve the effective model and calculate conductance G(T).

Main Results:

• Observed conductance G(T) = a - b√[T] at low temperatures, characteristic of the two-channel Kondo model.
• Calculated ground state impurity entropy as ln(2)/2, confirming Kondo model similarity.
• Identified a transition to a non-Kondo phase and the physics of the underscreened Kondo model at a quantum critical point upon chain stretching.

Conclusions:

• Monatomic gold chains with cobalt impurities exhibit two-channel Kondo physics.
• Chain length is a critical parameter controlling the transition between Kondo and non-Kondo phases.
• The study provides insights into quantum criticality in mesoscopic magnetic systems.