Ivar Giaever
1929–2025, Bergen, Norway
Norwegian-American physicist who demonstrated tunneling of single electrons between superconductors, directly measuring the superconducting energy gap.
A mechanical engineer from Trondheim who emigrated to Canada then joined General Electric, Giaever took up solid-state physics only at thirty. Studying oxide-insulated metal sandwiches in 1960, he showed that the tunneling current between two superconductors maps out the BCS density of states — turning tunnel junctions into a spectroscopic probe of the energy gap.
Nobel-winning work
Giaever shared the 1973 Nobel Prize for experimental discoveries about tunneling in superconductors. His junctions — superconductor–insulator–superconductor sandwiches — produced I–V curves whose kinks at voltage eV = 2Δ gave a direct reading of the BCS energy gap, including its temperature dependence and collapse at Tc.
When one electrode was normal metal, the linear tunneling conductance even measured the quasiparticle density of states. Giaever's technique validated BCS quantitatively and made tunneling spectroscopy a standard tool of condensed matter physics.
Workplaces: General Electric Research Laboratory, Rensselaer Polytechnic Institute
United States, Norway