Magnetic Single-Electron Transistor as a Tunable Model System for Kondo-Destroying Quantum Criticality

Abstract

Single-electron transistors attached to ferromagnetic leads can undergo a continuous quantum phase transition as their gate voltage is tuned. The corresponding quantum critical point separates a Fermi liquid phase from a non-Fermi liquid one. Here, we expound on the physical idea proposed earlier. The key physics is the critical destruction of the Kondo effect, which underlies a new class of quantum criticality that has been argued to apply to heavy fermion metals. Its manifestation in the transport properties is studied through an effective Bose-Fermi Kondo model; the bosonic bath, corresponding to the spin waves of the ferromagnetic leads, describes a particular type of sub-Ohmic dissipation. We also present results for general forms of sub-Ohmic dissipative bath, and consider in some detail the case with critical paramagons replacing spin waves. Finally, we discuss some delicate aspects in the theoretical treatment of the effect of a local magnetic field, particularly in connection with the frequently employed Non-Crossing Approximation.

4 pages, 3 figures, to appear in the proceedings of SCES 07 (the international conference on strongly correlated electron systems 2007)

References in corpus (7)

• The Kondo effect in C${}_{60}$ single-molecule transistors
• Multiple energy scales at a quantum critical point
• NRG study of the Kondo effect in the presence of itinerant-electron ferromagnetism
• Nonequilibrium Singlet-Triplet Kondo Effect in Carbon Nanotubes
• Quantum phase transitions in the Bose-Fermi Kondo model
• Quantum critical properties of the Bose-Fermi Kondo Model in a large-N limit
• Quantum Criticality in Ferromagnetic Single-Electron Transistors

Cited by in corpus (1)

• Scaling and Enhanced Symmetry at the Quantum Critical Point of the Sub-Ohmic Bose-Fermi Kondo Model