All three were working on research in physics at the then recently created University of São Paulo, amid a climate of great intellectual excitement and a breeding ground for a bright young generation of what would become the élite of Brazilian physics, such as César Lattes, Oscar Sala, Roberto Salmeron, Jayme Tiomno and Marcelo Damy de Souza Santos.
Accepting an invitation by Carlos Chagas Filho, Leite Lopes started to work in the same year the Institute of Biophysics of the Federal University of Rio de Janeiro, but soon moved to the University of São Paulo to take up graduate studies in quantum mechanics with his teacher, friend and sponsor, Mário Schenberg.
There, he had the opportunity to learn and work with giants of theoretical physics, such as Albert Einstein, Wolfgang Pauli and John von Neumann, despite the fact that most of the faculty was absent, involved in the Manhattan Project (the development of the first atomic bombs).
In 1946, he finished his doctoral dissertation, on the topic of the influence of the recoil of heavy particles on the nuclear potential energy, and returned to Rio de Janeiro.
Together with César Lattes, a young physicist from São Paulo who had achieved international fame due to his co-discovery of a new kind of nuclear particle, the pion (pi-meson), Leite Lopes was instrumental in creating in January 1949, in Rio de Janeiro, the Centro Brasileiro de Pesquisas Físicas (Brazilian Center for Research in Physics) (CBPF), a research center in theoretical physics (the first in Latin America), maintained by funds from Confederação Nacional de Indústrias (Brazilian Confederation of Industries), then presided by Euvaldo Lodi.