We study the effect of disorder on the London penetration depth in iron-based superconductors. The theory is based on a two-band model with quasi-two-dimensional Fermi surfaces, which allows for the coexistence region in the phase diagram between mag
netic and superconducting states in the presence of intraband and interband scattering. Within the quasiclassical approximation we derive and solve Eilenbergers equations, which include a weak external magnetic field, and provide analytical expressions for the penetration depth in the various limiting cases. A complete numerical analysis of the doping and temperature dependence of the London penetration depth reveals the crucial effect of disorder scattering, which is especially pronounced in the coexistence phase. The experimental implications of our results are discussed.
We develop a hydrodynamic description of the collective modes of interacting liquids in a quasi-one-dimensional confining potential. By solving Navier-Stokes equations we determine analytically excitation spectrum of sloshing oscillations. For parabo
lic confinement, the lowest frequency eigenmode is not renormalized by interactions and is protected from decay by the Kohn theorem, which states that center of mass motion decouples from internal dynamics. We find that the combined effect of potential anharmonicity and interactions results in the depolarization shift and final lifetime of the Kohn mode. All other excited modes of sloshing oscillations thermalize with the parametrically faster rates. Our results are significant for the interpretation of recent experiments with trapped Fermi gases that observed weak violation of the Kohn theorem.
We consider the two-dimensional electron gas confined laterally to a narrow channel by a harmonic potential. As the Zeeman splitting matches the intersubband separation the nonlocal spin polarization develops a minimum as reported by Frolov et al. [N
ature (London) 458, 868 (2009)]. This phenomenon termed Ballistic Spin Resonance is due to the degeneracy between the nearest oppositely polarized subbands that is lifted by spin-orbit coupling. We showed that the resonance survives the weak and short-range interaction. The latter detunes it and as a result shifts the Zeeman splitting at which the minimum in spin polarization occurs. Here this shift is attributed to the absence of Kohn theorem for the spin sloshing collective mode. We characterized the shift due to weak interaction qualitatively by analyzing the spin sloshing mode within the Fermi liquid phenomenology.
We study transport in the domain state, the so-called zero-resistance state, that emerges in a two-dimensional electron system in which the combined action of microwave radiation and magnetic field produces a negative absolute conductivity. We show t
hat the voltage-biased system has a rich phase diagram in the system size and voltage plane, with second- and first-order transitions between the domain and homogeneous states for small and large voltages, respectively. We find the residual negative dissipative resistance in the stable domain state.
We present a systematic study of the microwave-induced oscillations in the magnetoresistance of a 2D electron gas for mixed disorder including both short-range and long-range components. The obtained photoconductivity tensor contains contributions of
four distinct transport mechanisms. We show that the photoresponse depends crucially on the relative weight of the short-range component of disorder. Depending on the properties of disorder, the theory allows one to identify the temperature range within which the photoresponse is dominated by one of the mechanisms analyzed in the paper.
We show that the dynamic structure factor of a one-dimensional Bose liquid has a power-law singularity defining the main mode of collective excitations. Using the Lieb-Liniger model, we evaluate the corresponding exponent as a function of the wave vector and the interaction strength.
