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Berry's Phase in Manganese Oxides,

It's the Berry's!

behavior of Hall resistivity as a function of the magnetization of a manganese oxide sample
(Click here for a higher-resolution image.)

Some years ago, Pancharatnam discovered that light traveling a path in which its polarization is changed in succession exhibits interference effects, a consequence of the fact that successive rotations lead to the accumulation of phase, usually referred to as Berry's phase.

In manganese oxides that exhibit large (so-called colossal) magnetoresistive effects, the electrons that hop from one manganese atom to the next must rotate their quantum mechanical spin from being parallel to the magnetic moment of the starting atom to align with the atom to which they are hopping. As a consequence, these electrons also accumulate a Berry phase when the magnetic moments are imperfectly aligned, as they are at temperatures where the magneto-resistance is observed.

Professor Myron Salamon (experiment) and Professor Paul Goldbart (theory) have found, for the first time, that the existence of the Berry phase is immediately observable through the behavior of the Hall effect, which results here predominantly from the effect of an external magnetic field on the magnetization. The figure shows the behavior of the Hall resistivity, which is directly proportional to the Hall voltage, as a function of the magnetization of the sample for a sample that has been doped with lead in place of lanthanum. The solid curve is a theoretical calculation based on the combined action of the Berry phase and spin-orbit effects on the motion of charge carriers.

S. H. Chun et al., "Magnetotransport in Manganites and the Role of Quantal Phases: Theory and Experiment," Phys. Rev. Lett. 84, 757-760 (2000).


Find out more about Professor Salamon's and Professor Goldbart's research.

This work was supported in part by the U.S. Department of Energy, Grant No. DEFG-91ER45439, through the Frederick Seitz Materials Research Laboratory. Any opinion, findings, and conclusions or recommendations expressed herein are those of the authors and do not necessarily reflect the views of the Department of Energy.