Topological States in a One-Dimensional Fermi Gas with Attractive Interaction

Jonathan Ruhman, Erez Berg, Ehud Altman
2015 Physical Review Letters  
We describe a novel topological superfluid state, which forms in a one-dimensional Fermi gas with Rashba-like spin-orbit coupling, a Zeeman field and intrinsic attractive interactions. In spite of total number conservation and the presence of gapless excitations, Majorana-like zero modes appear in this system and can be linked with interfaces between two distinct phases that naturally form at different regions of the harmonic trap. As a result, the low lying collective excitations of the
more » ... tions of the system, including the dipole oscillations and the long-wavelength phonons, are doubly degenerate. While backscattering from point impurities can lead to a splitting of the degeneracies that scales algebraically with the system size, the smooth confining potential can only cause an exponentially small splitting. We show that the topological state can be uniquely probed by a pumping effect induced by a slow sweep of the Zeeman field from a high initial value down to zero field.
doi:10.1103/physrevlett.114.100401 pmid:25815908 fatcat:ucmceykxerf7rlrisazwd4kguu