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

Yıl 2017, , 31 - 37, 07.12.2017

Ali İhsan Göker

https://doi.org/10.25092/baunfbed.363752

Öz

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. 

Anahtar Kelimeler

Grafen, Kondo etkisi, kuantum noktacığı

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

Öz

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.

Anahtar Kelimeler

Graphene, Kondo effect, quantum dot

Kaynakça

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