### Séminaire de groupe

Helical gaps in interacting Rashba wires |

Thomas Schmidt |

jeudi 16 février 2017 , 10h25 |

Salle de séminaire du groupe de Physique Statistique |

A partially gapped spectrum due to the application of a magnetic field is one of the main probes of Rashba spin-orbit coupling in nanowires. Such a "helical gap" manifests itself in the linear conductance, as well as in dynamic response functions such as the spectral function, the structure factor, or the tunnelling density of states. We will present results about the signature of the helical gap in these observables with a particular focus on the interplay between Rashba spin-orbit coupling and electron-electron interactions. In a quasi-one-dimensional wire, interactions can open a helical gap even without magnetic field. To show how the two types of helical gaps, caused by magnetic fields or interactions, can be distinguished in experiments, we will present the dynamic response functions calculated using bosonization, a renormalization group analysis, and the exact form factors of the emerging sine-Gordon model. For special interaction strengths, the results can be verified by refermionization. The helical gap typically occurs at low electron densities where the Coulomb energy dominates over the kinetic energy. To address this strongly correlated limit, we have also investigated Rashba wires using Wigner crystal theory. To interplay of Rashba spin-orbit coupling and a magnetic field then leads to an effective spiral magnetic field. The helical gap exists even in the limit of strong interactions but its dependence on electron density differs significantly from the weakly interacting case. In particular, the critical magnetic field for opening the gap becomes an oscillatory function of electron density. |