title: Leggett Modes and the Anderson-Higgs Mechanism in Superconductors without Inversion Symmetry.
abstract: We develop a microscopic and gauge-invariant theory for collective modes resulting from the phase of the superconducting order parameter in noncentrosymmetric superconductors. Considering various crystal symmetries, we derive the corresponding gauge mode ω_{G}(q) and find, in particular, new Leggett modes ω_{L}(q) with characteristic properties that are unique to noncentrosymmetric superconductors. We calculate their mass and dispersion that reflect the underlying spin-orbit coupling and thus the balance between triplet and singlet superconductivity occurring simultaneously. Finally, we demonstrate the role of the Anderson-Higgs mechanism: while the long-range Coulomb interaction shifts ω_{G}(q) to the condensate plasma mode ω_{P}(q), it leaves the mass Λ_{0} of the new Leggett mode unaffected and only slightly modifies its dispersion.
authors.affiliation: Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany.
authors.forename: Nikolaj
authors.initials: N
authors.lastname: Bittner
authors.affiliation: Walther-Meissner-Institut für Tieftemperaturforschung, D-85748 Garching, Germany.
authors.forename: Dietrich
authors.initials: D
authors.lastname: Einzel
authors.affiliation: Theoretische Physik, ETH-Zürich, CH-8093 Zürich, Switzerland.
authors.forename: Ludwig
authors.initials: L
authors.lastname: Klam
authors.affiliation: Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Manske