Kondo effects in quantum point contacts
Ben-Gurion University, Israel
Quantum point contacts (QPCs), are the basic building blocks of any
mesoscopic structure, and display quantized conductance, reflecting
the quantization of the number of transparent channels.
An additional feature, coined the "0.7 anomaly", has been observed in
almost all QPCs, and has been a subject of intensive debate in the
last couple of decades. In the past we have attributed this feature to
the emergence of a quasi-localized state at the QPC, which explains
all the phenomenology of the Kondo effect.
In this talk I will describe two new experiments, and relevant
theories, one which measured the thermoelectric power through the QPC,
and another which measured the conductance through length-tunable
QPC. The experimental findings support the picture of the localized
state(s). Interestingly, with increasing QPC length, it was found that
both the 0.7 anomaly and the zero bias peak in the differential
conductance oscillate and peridically split with channel length,
supporting the idea that the number of the localized state increases
with length, leading to an alternating Kondo effect.