Spin splitting and Kondo effect in quantum dots coupled to noncollinear ferromagnetic leads

Daisuke Matsubayashi, Mikio Eto

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

We study the Kondo effect in a quantum dot coupled to two noncollinear ferromagnetic leads. First, we study the spin splitting δ = ↓ - ↑ of an energy level in the quantum dot by tunnel couplings to the ferromagnetic leads using the poor man's scaling method. The spin splitting takes place in an intermediate direction between magnetic moments in the two leads. δ p cos2 (θ 2) + v2 sin2 (θ 2), where p is the spin polarization in the leads, θ is the angle between the magnetic moments, and v is an asymmetric factor of tunnel barriers (-1<v<1). Hence the spin splitting is always maximal in the parallel alignment of two ferromagnets (θ=0) and minimal in the antiparallel alignment (θ=π). Second, we calculate the Kondo temperature TK. The scaling calculation yields an analytical expression of TK as a function of θ and p, TK (θ,p), when δ TK. TK (θ,p) is a decreasing function with respect to p cos2 (θ 2) + v2 sin2 (θ 2). When δ is relevant, we evaluate TK (δ,θ,p) using the slave-boson mean-field theory. The Kondo resonance is split into two by finite δ, which results in the spin accumulation in the quantum dot and suppression of the Kondo effect.

Original languageEnglish
Article number165319
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume75
Issue number16
DOIs
Publication statusPublished - 2007 Apr 24

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Kondo effect
Semiconductor quantum dots
quantum dots
Magnetic moments
Tunnels
Bosons
Mean field theory
Spin polarization
tunnels
Electron energy levels
magnetic moments
alignment
scaling
bosons
energy levels
retarding
polarization
Temperature

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Spin splitting and Kondo effect in quantum dots coupled to noncollinear ferromagnetic leads. / Matsubayashi, Daisuke; Eto, Mikio.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 75, No. 16, 165319, 24.04.2007.

Research output: Contribution to journalArticle

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