A. Roman

Publications (2)0 Total impact

• Source

  Available from: ArXiv

  Article: The thermal conductance of a two-channel Kondo model

  C. P. Moca, A. Roman, D. C. Marinescu
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  ABSTRACT: A theory of thermal transport in a two-channel Kondo system, such as the one formed by a small quantum dot coupled to two leads and to a larger dot, is formulated. The interplay of the two screening constants allows an exploration of the Fermi liquid and non-Fermi liquid regimes. By using analytical, as well as numerical renormalization group methods, we study the temperature dependence of the thermal conductance and the Lorentz number. We find that in the low temperature limit, the Lorentz number attains its universal value, irrespective of the nature of the ground state.
  06/2011;
• Article: Quantum phase transition in a gapped Anderson model: A numerical renormalization group study

  C. P. Moca, A. Roman
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  ABSTRACT: We use the numerical renormalization group method to investigate the spectral properties of a single-impurity Anderson model with a gap δ across the Fermi level in the conduction-electron spectrum. For any finite δ>0, at half filling the ground state of the system is always a doublet. Away from half filling a quantum phase transition (QPT) occurs as function of the gap value δ, and the system evolves from the strong-coupling (SC) Kondo-type state, corresponding to δ<δC toward a localized moment (LM) regime for δ>δC. The opening of the gap leads to the formation of one (two) bound states when the system is in the SC (LM) regime. The evolution across the QPT of their positions and the corresponding weights together with the dynamic properties of the model are investigated.
  Phys. Rev. B. 81(23).