sentences:  In 1964, Dmitri joined the group of Zhores Alferov at Ioffe Physical-Technical Institute of the Russian Academy of Sciences in Leningrad.At the time, Alferov's team was among the very few research groups in the world that studied heterojunctions in semiconductors.In 2000, Zhores Alferov and Herbert Kroemer were awarded the Nobel Prize for their pioneering work.