Direct observation of the Aharonov-Casher phase
  Ring structures fabricated from HgTe/HgCdTe quantum wells have been used to study Aharonov-Bohm type conductance oscillations as a function of Rashba spin-orbit splitting strength. We observe non-monotonic phase changes indicating that an additional phase factor modifies the electron wave function. We associate these observations with the Aharonov-Casher effect. This is confirmed by comparison with numerical calculations of the magneto-conductance for a multichannel ring structure within the Landauer-B\"uttiker formalism. 
M. Koenig, A. Tschetschetkin, E.M. Hankiewicz, Jairo Sinova, V. Hock,   V. Daumer, M. Schaefer, C.R. Becker, H. Buhmann, and...