Bertrand (Bert) Halperin
Professor at Harvard University
Biography
Place of Birth: Brooklyn, NY
Date of Birth: December 6, 1941
Studied at: Harvard University; Class of 1961
Currently teaches Mathematics and Natural Philosophy at Harvard University
Contributions to Physics
With the help of David R. Nelson, he worked out a theory of two-dimensional melting, and predicted the hexatic phase. He also contributed to the Quantum Hall Effect, which has to do with two-dimensional electrons.
Theories
Hexatic Phase: The hexatic phase occurs between solid and liquid in which two transitions take place. The first occurs when the solid undergoes a dislocation unbinding transition to the hexatic phase. The second is the disclination unbinding transition to the isotropic (liquid) phase. A dislocation unbinding transition occur as a defect within a crystal structure. Basically, dislocations are areas where atoms are out of position and they are generated and move when stress is applied.
Quantum Hall Effect: This is observed in two-dimensional electron systems that are put under low temperatures and strong magnetic fields. Basically, it has to do with resistance as a function of integers or fractions.
Sources
-- https://www.nde-ed.org/EducationResources/CommunityCollege/Materials/Structure/linear_defects.htm
--http://www.pha.jhu.edu/~qiuym/qhe/qhe.html