After her PhD, she joined Polytechnic University of New York as a postdoctoral research fellow in 1988 and was appointed Assistant Professor in 1989. Cohen first joined Imperial College London in 1993 funded by a Royal Society University Research Fellowship. She became a Reader in Solid State in 2003 and a Professor in 2006. Between 2008 - 2013, she was Head of Solid State Physics, one of the largest research groups at Imperial. Cohen is interested in alternatives to standard models of refrigeration, using magnetic materials. Magnetic refrigeration could provide a "green" alternative to traditional fridges, using 20 - 30% less energy. In 2009 her group uncovered the mechanism behind cooling crystals, known as the magnetocaloric effect.