P ve n katkılı grafen elektrotlara asimetrik bağlı güçlü korelasyonlu bir kuantum noktacığında gerçek zamanlı elektron dinamikleri

Abstract

Kesişmeme yaklaşımını kullanarak p ve n katkılı grafen elektrotlara asimetrik olarak bağlanmış güçlü korelasyonlu bir kuantum noktacığı boyunca kuantum taşınmasını araştırdık. Kuantum noktacığı bir kapı voltajı yoluyla aniden elektrotların Fermi düzeyine yakın bir noktaya getirildiğinde meydana gelen iletkenliğin karmaşık dalgalanmalar gösterdiğini bulduk. Bu dalgalanmaların ortam sıcaklığı Kondo sıcaklığının üstüne çıktığında ve asimetri faktörü azaldığında giderek sönümlendiğini tespit ettik. Gözlemlenen dalgalanmaların Fourier dönüşümü yoluyla analizi sonucunda, titreşimlerin n katkılı grafende Dirac noktası ve bant kenarının Fermi düzeyine uzaklığıyla orantılı iki farklı frekansta gerçekleşirken p katkılı grafende bant kenarının Fermi düzeyine uzaklığıyla orantılı sadece tek bir titreşim frekansı olduğunu bulduk. Bu durumu Fermi düzeyindeki gelişen Kondo rezonansının elektrotların durumlar yoğunluğundaki van Hove tekillikleriyle dinamik girişimini öneren bir mikroskopik teoriye bağladık. 

Keywords

• Grafen,Kondo etkisi,kuantum noktacığı

Real time electron dynamics in a strongly correlated quantum dot asymmetrically coupled to p and n doped graphene electrodes

Abstract

We investigated the quantum transport through a strongly correlated quantum dot asymmetrically coupled to p and n doped graphene electrodes invoking the non-crossing approximation. We found that the conductance exhibits complex fluctuations when the dot level is abruptly moved to a position close to the Fermi level of the electrodes via a gate voltage. We determined that these fluctuations get gradually suppressed when the ambient temperature starts to exceed the Kondo temperature and the asymmetry factor decreases. As a result of the analysis of these fluctuations via the Fourier transform, we found that while the oscillations take place in two distinct frequencies which are proportional to the distance of the Dirac point and the band edge to the Fermi level for the n doped graphene, there exists only one oscillation frequency proportional to the distance of the band edge to the Fermi level. We attributed this situation to a microscopic theory which suggests the dynamical interference of the developing  Kondo resonance at the Fermi level with the van Hove singularities at the density of states of the electrodes.

Keywords

• Graphene,Kondo effect,quantum dot

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