Hans Bethe introduced his now-famous ansatz to obtain the energy eigenstates of the one-dimensional version of Werner Heisenberg’s model of interacting, localized spins in a solid. 1,2 Although it is among Bethe’s most cited works and has a wide range of applications, it is rarely included in the graduate physics curriculum except at the advanced level. The 75th anniversary of the Bethe ansatz is appropriately marked by reflecting on the impact of Bethe’s result on modern physics, ranging from its profound influence on the field of exactly solved models in statistical mechanics to insights into the subtle nature of quantum many-body effects observed in cold quantum gases.
Bethe (figure 1) completed his PhD in theoretical physics under Arnold Sommerfeld in 1928. During his subsequent time at the University of Munich, Bethe used a traveling fellowship to go to Cambridge in the fall of 1930 and to Rome during the...
