In 1974, he became a subject of controversy when the investigations on suspected espionage was launched by the German internal security agency, the Stasi but all charges were dropped later on.

[2][3] In 1935, Hartmann found an employment with Siemens AG and was a research associate of Gustav Hertz who had him worked on a semiconductor technology.

In mid-May 1945, the Russian physicists Georgy Flerov and Lev Artsimovich, in NKVD colonel's uniforms, compelled Karl Zimmer to take them to the location of Nikolaus Riehl and his staff, who had evacuated their Auergesellschaft AG facilities to west of Berlin, hoping to be in an area occupied by the American or British military forces; Riehl was the scientific director for Auergesellschaft and involved in support of the Uranium Club from its earlier times.

Riehl was taken in Soviet custody and initially held in search team's facility in Friedrichshagen neighborhood of Berlin for a week before being flown to Russia to head a group, at the Plant No.

[8][9] During this time, German physicist, Manfred von Ardenne, director of his private laboratory Forschungslaboratorium für Elektronenphysik (lit.

Research Laboratory for Electron Physics),[10] Gustav Hertz, Nobel laureate and director of Research Laboratory II at Siemens, Peter Adolf Thiessen, ordinarius professor at the University of Berlin and director of the Kaiser-Wilhelm Institut für physikalische Chemie und Elektrochemie in Dahlem, and Max Volmer, ordinarius professor and director of the Physical Chemistry Institute at the Technical University of Berlin, had made a pact.

The objectives of their pact were threefold: Before the end of World War II, Thiessen, a member of the Nazi Party, had Communist contacts.

Hertz was made head of Institute G, in Agudseri (Agudzery),[14][15] about 10 km southeast of Sukhumi and a suburb of Gul’rips (Gulrip’shi).

Hartmann was flown there on 13 June and worked on the electromagnetism in Agudseri (Agudzery), at Institute G, directed by Gustav Hertz.

ZMD produced the GDR's first 1-megabyte DRAM U61000 in 1988 and is today a fabless semiconductor company named ZMDI Hartmann had been under surveillance in the Soviet Union, since 1947, for his "anti-Soviet statements and attitudes."

In 1966, he fought receipt of a Soviet security clearance, as he feared this would limit his travel in and scientific contact with the West.