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Point-Contact Spectroscopy

100%

Jansen A.

Acta Physica Polonica A

1992

vol. 82

issue 4

539-550

In a small metallic constriction ("point contact") the transport of electrons is ballistic. The applied voltage V tunes a well-defined non-equilibrium energy eV of electrons. The nonlinear current-voltage characteristics can be used to perform energy-resolved spectroscopy of the inelastic scattering of electrons with elementary excitations in metal (e.g. phonons, magnons, crystal-field levels, paramagnetic impurities). The basic elements of the point--contact method and its applications will be discussed. In recent point-contact experiments the observed phenomena (weak localization, resistance fluctuations) need a description that goes beyond the classical Boltzmann approach of electronic transport in a point contact. In analogy to observed effects in the diffusive transport in mesoscopic systems, these phenomena are explained by considering quantum-interference effects in the ballistic transport near the contact region related to the wave character of the electrons.

Magnetic Field Dependent Effective Mass in the Organic Superconductor κ-(BEDT-TTF)_{2}I_{3}

39%

Balthes E., Schweitzer D., Heinen I., Keller H., Biberacher W., Jansen A., Steep E.

Acta Physica Polonica A

1995

vol. 87

issue 4-5

767-772

κ-(BEDT-TTF)_{2}I_{3} is an electronically extreme two-dimensional organic metal with a superconducting transition at around 4 K. In magnetic fields above 12 T the effective mass, as obtained from the temperature dependence of the amplitudes of Shubnikov-de Haas oscillations, is magnetic field dependent as long as the magnetic field is arranged perpendicular to the conducting planes. In contrast to this, by turning the magnetic field by 27° or even only 9° the observed effective mass (as obtained from Shubnikov-de Haas and de Haas-van Alphen measurements) is field independent. We suppose that the occurrence of anyons at temperatures below 1 K in fields above 12 T is the reason for the observed field dependence of the effective mass.

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2 Acta Physica Polonica A

1 1995

1 1992

2 Jansen A.

1 Balthes E.

1 Biberacher W.

1 Heinen I.

1 Keller H.

1 Schweitzer D.

1 Steep E.

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Point-Contact Spectroscopy

Magnetic Field Dependent Effective Mass in the Organic Superconductor κ-(BEDT-TTF)_{2}I_{3}