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Detection of Berry’s Phase in a Bulk Rashba Semiconductor

Science  20 Dec 2013:
Vol. 342, Issue 6165, pp. 1490-1493
DOI: 10.1126/science.1242247

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Spin Berry's Phase

When a quantum mechanical system performs an adiabatic cyclic path in the space of the parameters that affect its state (such as, for example, the magnetic field) its wave function may acquire an additional phase rather than go back to its original value. This quantity, called the Berry's phase, is associated with the topological properties of the parameter space and has been observed in materials such as graphene and bismuth. Murakawa et al. (p. 1490) observe a Berry's phase equal to π in the material BiTeI in which the phenomenon is predicted to be a consequence of a very strong coupling of spin and orbital degrees of freedom realized through the so-called Rashba effect.

Abstract

The motion of electrons in a solid has a profound effect on its topological properties and may result in a nonzero Berry’s phase, a geometric quantum phase encoded in the system’s electronic wave function. Despite its ubiquity, there are few experimental observations of Berry’s phase of bulk states. Here, we report detection of a nontrivial π Berry’s phase in the bulk Rashba semiconductor BiTeI via analysis of the Shubnikov–de Haas (SdH) effect. The extremely large Rashba splitting in this material enables the separation of SdH oscillations, stemming from the spin-split inner and outer Fermi surfaces. For both Fermi surfaces, we observe a systematic π-phase shift in SdH oscillations, consistent with the theoretically predicted nontrivial π Berry’s phase in Rashba systems.

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