Mystery of Excess Low Energy States in a Disordered Superconductor in a Zeeman Field

Abstract

Tunneling density of states measurements of disordered superconducting (SC) Al films in high Zeeman fields reveal a significant population of subgap states which cannot be explained by standard BCS theory. We provide a natural explanation of these excess states in terms of a novel disordered Larkin-Ovchinnikov (dLO) phase that occurs near the spin-paramagnetic transition at the Chandrasekhar-Clogston critical field. The dLO superconductor is characterized by a pairing amplitude that changes sign at domain walls. These domain walls carry magnetization and support Andreev bound states, which lead to distinct spectral signatures at low energy.

5 pages, 4 figures, plus supplementary section describing methods (2 pages)

References in corpus (11)

• Spin-Imbalance in a One-Dimensional Fermi Gas
• Nature of the superconductor-insulator transition in disordered superconductors
• Imbalanced Feshbach-resonant Fermi gases
• Field Evolution of Coexisting Superconducting and Magnetic Orders in CeCoIn${}_5$
• Observation of Giant Positive Magnetoresistance in a Cooper Pair Insulator
• Larkin-Ovchinnikov state in resonant Fermi gas
• Large Range of Stability of Larkin-Ovchinnikov States for Imbalanced Fermi Gases in Optical Lattices
• Spin-Resolved Tunneling Studies of the Exchange Field in EuS/Al Bilayers
• Spectral signatures of the Fulde-Ferrell-Larkin-Ovchinnikov order parameter in one-dimensional optical lattices
• Fermi-liquid effects in the gapless state of marginally thin superconducting films
• Pairing resonance as a normal-state spin probe in ultra-thin Al films

Cited by in corpus (11)

• Theoretical Studies of Superconductor-Insulator Transitions
• Evidence of Andreev bound states as a hallmark of the FFLO phase in $\kappa$-(BEDT-TTF)${}_2$Cu(NCS)${}_2$
• Fulde-Ferrell-Larkin-Ovchinnikov state of two-dimensional imbalanced Fermi gases
• Realizing Fulde-Ferrell Superfluids via a Dark-State Control of Feshbach Resonances
• Zeeman-limited Superconductivity in Crystalline Al Films
• Dimensional Crossover in a Spin-imbalanced Fermi gas
• Asymmetric Avalanches in the Condensate of a Zeeman-limited Superconductor
• Spectroscopic signatures of the Larkin-Ovchinnikov state in the conductance characteristics of a normal-metal/superconductor junction
• Fulde-Ferrell-Larkin-Ovchinnikov state in strongly correlated d-wave superconductors
• Critical field behavior of a multiply connected superconductor in a tilted magnetic field
• Spin-Polarized Tunneling in Critically Disordered Be-Al Bilayers