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Exploring the phase diagram of the two-impurity Kondo problem.
A Spinelli1, M Gerrits1, R Toskovic1
1Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
Nature Communications
|December 1, 2015
Summary
Researchers studied two magnetic cobalt (Co) atoms on a surface, revealing a new phase where both atoms are simultaneously screened in a magnetic field. This finding unlocks previously inaccessible correlated phenomena in coupled impurity systems.
Area of Science:
- Condensed Matter Physics
- Surface Science
- Quantum Many-Body Physics
Background:
- Exchange-coupled Kondo impurities in a magnetic field exhibit complex correlated phenomena.
- Scanning tunnelling microscopy (STM) on magnetic atoms is a key platform for studying coupled impurities.
- High Kondo temperatures in typical systems limit magnetic field-dependent studies and access to phase space.
Purpose of the Study:
- To investigate coupled magnetic impurities with low Kondo temperatures to access field-dependent phases.
- To explore the phase space of exchange-coupled Co impurities under a magnetic field.
- To characterize the Kondo screening of individual impurities in a coupled system.
Main Methods:
- Fabrication of pairs of Cobalt (Co) atoms on an insulating Cu2N/Cu(100) surface.
- Experimental setup designed for low Kondo temperatures (2.6 K) and comparable interaction strengths.
- Application of a strong magnetic field to probe new phases.
- Measurement of differential conductance spectra.
- Simulation of spectra using a third-order transport model.
Main Results:
- Successfully created Co atom pairs with low Kondo temperatures (2.6 K) and tunable interaction strengths.
- Accessed a novel phase by applying a sufficiently strong magnetic field, where both coupled impurities are simultaneously screened.
- Independently determined the degree of Kondo screening for each impurity by comparing experimental spectra to theoretical simulations.
Conclusions:
- Demonstrated a method to access previously inaccessible phases of coupled Kondo impurities using low-temperature and magnetic field techniques.
- The study provides a new platform for investigating correlated phenomena in engineered quantum impurity systems.
- The developed model accurately describes the Kondo screening in the observed phases.
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