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Volumn 79, Issue 4, 2009, Pages

Supercurrent and multiple singlet-doublet phase transitions of a quantum dot Josephson junction inside an Aharonov-Bohm ring

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EID: 59249099414     PISSN: 10980121     EISSN: 1550235X     Source Type: Journal    
DOI: 10.1103/PhysRevB.79.045110     Document Type: Article
Times cited : (21)

References (46)
  • 21
    • 4344596766 scopus 로고    scopus 로고
    • 10.1103/PhysRevLett.93.047002;
    • F. Siano and R. Egger, Phys. Rev. Lett. 93, 047002 (2004) 10.1103/PhysRevLett.93.047002
    • (2004) Phys. Rev. Lett. , vol.93 , pp. 047002
    • Siano, F.1    Egger, R.2
  • 22
    • 18044393810 scopus 로고    scopus 로고
    • 10.1103/PhysRevLett.94.039902
    • F. Siano and R. Egger, Phys. Rev. Lett. 94, 039902 (E) (2005). 10.1103/PhysRevLett.94.039902
    • (2005) Phys. Rev. Lett. , vol.94 , pp. 039902
    • Siano, F.1    Egger, R.2
  • 34
  • 35
    • 59249094876 scopus 로고    scopus 로고
    • This was already pointed out in Ref..
    • This was already pointed out in Ref..
  • 37
    • 59249089544 scopus 로고    scopus 로고
    • The FRG approximation introduced in Sec. 3 does not allow for computing the impurity spectral function. Thus, we cannot address the question whether there is actually a Kondo resonance or a BCS gap governing the low-energy behavior for the problem at hand. However, numerical renormalization-group calculations for the simple quantum dot Josephson junction (td =0) (Ref.) as well as for the nonsuperconducting setup (Δ=0) (Ref.) showed that at sufficiently large U the physics is crucially influenced by the Kondo effect. It is reasonable to assume that Kondo correlations are still present for the problem at hand.
    • The FRG approximation introduced in Sec. 3 does not allow for computing the impurity spectral function. Thus, we cannot address the question whether there is actually a Kondo resonance or a BCS gap governing the low-energy behavior for the problem at hand. However, numerical renormalization-group calculations for the simple quantum dot Josephson junction (td =0) (Ref.) as well as for the nonsuperconducting setup (Δ=0) (Ref.) showed that at sufficiently large U the physics is crucially influenced by the Kondo effect. It is reasonable to assume that Kondo correlations are still present for the problem at hand.
  • 39
    • 59249106756 scopus 로고    scopus 로고
    • Focusing on the limit of small Δ/ TK, this issue was previously raised in Ref.. However, the author fails to treat the noninteracting limit U=0 correctly (Ref.), rendering his results a priori questionable.
    • Focusing on the limit of small Δ/ TK, this issue was previously raised in Ref.. However, the author fails to treat the noninteracting limit U=0 correctly (Ref.), rendering his results a priori questionable.
  • 42
  • 43
    • 59249103695 scopus 로고    scopus 로고
    • In the discussion of the phase boundary we implicitly assume that the hybridization strength Γ is chosen as the unit of energy.
    • In the discussion of the phase boundary we implicitly assume that the hybridization strength Γ is chosen as the unit of energy.
  • 44
    • 59249087673 scopus 로고    scopus 로고
    • Since our FRG scheme turns out to be quantitatively reliable only up to some intermediate Coulomb interaction U/Γ≈8 (where Kondo correlations start to become important), we cannot describe the singlet-doublet phase transition in the extreme limit of Δ/Γ≪1 (as this would require TK/Γ≪1), no matter which quantity is used to describe the phase boundary. However, for the simple quantum dot Josephson junction (td =0), it was demonstrated that generic physics shows up for small values of TK /Δ (but not necessarily extremely small TK itself). Since we do not observe any qualitative changes apart from an overall increase in the size of the singlet phase in going from Δ=∞ to Δ/Γ≈0.2, it is reasonable to assume that the same holds for the problem at hand.
    • Since our FRG scheme turns out to be quantitatively reliable only up to some intermediate Coulomb interaction U/Γ≈8 (where Kondo correlations start to become important), we cannot describe the singlet-doublet phase transition in the extreme limit of Δ/Γ≪1 (as this would require TK /Γ≪1), no matter which quantity is used to describe the phase boundary. However, for the simple quantum dot Josephson junction (td =0), it was demonstrated that generic physics shows up for small values of TK /Δ (but not necessarily extremely small TK itself). Since we do not observe any qualitative changes apart from an overall increase in the size of the singlet phase in going from Δ=∞ to Δ/Γ≈0.2, it is reasonable to assume that the same holds for the problem at hand.
  • 45
    • 59249100154 scopus 로고    scopus 로고
    • For the simple quantum dot Josephson junction (td =0), it was previously observed that in the doublet phase the supercurrent obtained from the FRG is completely independent of both the two-particle interaction strength U and the impurity energy (Ref.). Even though this is an artifact of the approximative approach, numerical RG calculations showed that physical properties only vary slightly in this regime (Ref.).
    • For the simple quantum dot Josephson junction (td =0), it was previously observed that in the doublet phase the supercurrent obtained from the FRG is completely independent of both the two-particle interaction strength U and the impurity energy (Ref.). Even though this is an artifact of the approximative approach, numerical RG calculations showed that physical properties only vary slightly in this regime (Ref.).
  • 46
    • 59249097023 scopus 로고    scopus 로고
    • Some generalized perturbative approach (Ref.) could be employed in order to get some intuitive understanding why J can become negative in the singlet phase. This is, however, out of the scope of this paper.
    • Some generalized perturbative approach (Ref.) could be employed in order to get some intuitive understanding why J can become negative in the singlet phase. This is, however, out of the scope of this paper.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.