Transport through quantum dots: a combined DMRG and embedded-cluster approximation study

Journal Article · Tue Jan 01 04:00:00 EST 2008 · European Physical Journal - Applied Physics

OSTI ID:961788

Heidrich-Meisner, Fabian ^[1]; Martins, G. B. ^[2]; Busser, C. A. ^[2]; Al Hassanieh, Khaled A ^[1]; Feiguin, A. E. ^[3]; Chiappe, G. ^[4]; Anda, E. V. ^[5]; Dagotto, Elbio R ^[1]

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1. ORNL
2. Oakland University, Rochester, MI
3. University of Maryland
4. Universidad de Alicante
5. Pontificia Universidade, Brazil

The numerical analysis of strongly interacting nanostructures requires powerful techniques. Recently developed methods, such as the time-dependent density matrix renormalization group (tDMRG) approach or the embedded-cluster approximation (ECA), rely on the numerical solution of clusters of finite size. For the interpretation of numerical results, it is therefore crucial to understand finite-size effects in detail. In this work, we present a careful finite-size analysis for the examples of one quantum dot, as well as three serially connected quantum dots. Depending on odd-even effects, physically quite different results may emerge from clusters that do not differ much in their size. We provide a solution to a recent controversy over results obtained with ECA for three quantum dots. In particular, using the optimum clusters discussed in this paper, the parameter range in which ECA can reliably be applied is increased, as we show for the case of three quantum dots. As a practical procedure, we propose that a comparison of results for static quantities against those of quasi-exact methods, such as the ground-state density matrix renormalization group (DMRG) method or exact diagonalization, serves to identify the optimum cluster type. In the examples studied here, we find that to observe signatures of the Kondo effect in finite systems, the best clusters involving dots and leads must have a total z-component of the spin equal to zero.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 961788
• Journal Information: European Physical Journal - Applied Physics, Journal Name: European Physical Journal - Applied Physics Journal Issue: 4 Vol. 67; ISSN 1286-0042; ISSN EPAPFV
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
APPROXIMATIONS
CHARGED-PARTICLE TRANSPORT
DENSITY MATRIX
KONDO EFFECT
NANOSTRUCTURES
NUMERICAL ANALYSIS
NUMERICAL SOLUTION
QUANTUM DOTS
RENORMALIZATION
SIZE
SPIN