Quantum size effects on the perpendicular upper critical field in ultrathin lead films.

Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China.
Physical Review Letters (Impact Factor: 7.73). 01/2006; 95(24):247005. DOI: 10.1103/PhysRevLett.95.247005
Source: PubMed

ABSTRACT We report the thickness-dependent (in terms of atomic layers) oscillation behavior of the perpendicular upper critical field Hc2perpendicular in the ultrathin lead films at the reduced temperature (t = T/Tc). Distinct oscillations of the normal-state resistivity as a function of film thickness have also been observed. Compared with the Tc oscillation, the Hc2perpendicular shows a considerable large oscillation amplitude and a pi phase shift. The oscillatory mean free path caused by the quantum size effect plays a role in Hc2perpendicular oscillation.

  • [Show abstract] [Hide abstract]
    ABSTRACT: The quasi two-dimensional electron gas on a metal film can transmit to the surface even minute mechanical disturbances occurring in the depth, thus allowing the gentlest of all surface probes, helium atoms, to perceive the vibrations of the deepest atoms via the induced surface-charge density oscillations. A density functional perturbation theory (DFPT) and a helium atom scattering study of the phonon dispersion curves in lead films of up to 7 mono-layers on a copper substrate show that: (a) the electron-phonon interaction is responsible for the coupling of He atoms to in-depth phonon modes; and (b) the inelastic HAS intensity from a given phonon mode is proportional to its electron-phonon coupling. The direct determination of mode-selected electron-phonon coupling strengths has great relevance for understanding superconductivity in thin films and two-dimensional systems.
    Physical Chemistry Chemical Physics 01/2014; · 4.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Using a low-temperature scanning tunneling microscope, we investigated the superconducting gap of single-crystalline Pb islands, approximately 100 nm in diameter with 11-13 monolayers (3-4 nm) in thickness, under magnetic fields. The superconducting gap was observed under magnetic fields up to 2.2 T, higher than the critical field of bulk Pb. The critical fields of the Pb islands were evaluated from the magnetic field dependence of the zero-bias conductances. We found that the critical field depends on the volume V of the Pb islands as V-1/2.
    Japanese Journal of Applied Physics 10/2007; 46(36):L880-L882. · 1.07 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In multiband superconductivity, the case where the single electron hopping between different Fermi surface spots of different symmetry is forbidden by selection rules is recently attracting a large interest. The focus is addressed to superconductivity made of multiple condensates with different symmetry where the chemical potential crosses a 2.5 Lifshitz transition. This can now be investigated experimentally by fine-tuning of the chemical potential in the range of tens meV around a band edge using gate voltage control. We discuss here the case of the two-dimensional electron gas (2DEG), at the interface between two insulating oxides confined within a slab of 5 nanometers thickness, where the electronic structure is made of subbands generated by quantum size effects. We focus on the case of the BCS-BEC transition in the upper subband for different pairing strength in the shallow Fermi surface.
    Journal of Physics Conference Series 12/2013; 529(1).

Full-text (2 Sources)

Available from
May 22, 2014