Synopsis: Dirac connection

Ballistic electron transport through a clean superconductor with d-wave symmetry has features in common with graphene.
Synopsis figure
Illustration: J. K. Asbóth et al., Phys. Rev. B (2009)

In response to a voltage, the electrical current in a pure sheet of graphene diminishes as 1/L, where L is the length over which the current is transmitted. This form of scaling, called pseudodiffusive because of its similarity to diffusion in a random potential, occurs when L is less than the width of the sheet and the mean free path.

In graphene, pseudodiffusion occurs because the electrons behave like massless Dirac fermions. Now, in a paper appearing in Physical Review B, János Asbóth and collaborators at Leiden University in the Netherlands calculate the transmission of electrons and holes between two normal-metal electrodes, separated over a distance L by a clean d-wave superconductor. Asbóth et al. find that the transmitted electrical and thermal currents both have the pseudodiffusive 1/L scaling characteristic of massless Dirac fermions—regardless of the presence of tunnel barriers at the metal-superconductor interfaces—as long as L is larger than the superconducting coherence length and smaller than the width of the superconductor and the mean free path. This occurs because the d-wave superconductor forms ballistic conduction channels for coupled electron-hole excitations that are described by an anisotropic two-dimensional Dirac equation analogous to that of graphene. This finding is likely to spur experimental efforts to search for pseudodiffusive transmission in clean single crystals of high-Tc cuprates. – Sarma Kancharla


Announcements

More Announcements »

Subject Areas

SuperconductivityGraphene

Next Synopsis

Related Articles

Viewpoint: A Boost for Superconducting Logic
Superconductivity

Viewpoint: A Boost for Superconducting Logic

A new choice of materials leads to more practically useful superconducting spin valves. Read More »

Viewpoint: The Quantum Hall Effect Gets More Practical
Magnetism

Viewpoint: The Quantum Hall Effect Gets More Practical

Thin films of magnetic topological insulators can exhibit a nearly ideal quantum Hall effect without requiring an applied magnetic field. Read More »

Synopsis: Superconductors Under Pressure
Superconductivity

Synopsis: Superconductors Under Pressure

The coupling of electrons to anharmonic crystal vibrations may explain the record high-temperature superconductivity in highly pressurized hydrogen sulfide. Read More »

More Articles