Collaborative Research: Collective Mode Spectroscopy in Unconventional Superconductors

John B. Ketterson, Northwestern University, DMR 0509357

Meander line

CeCoIn5

Pin Pout

CeCoIn5

We exploit a novel microwave transmission technique based on a copper-wire meander line to study the microwave absorption in CeCoIn5.

The measurement cell (shown in Fig. 1) consists of a meander line sandwiched between the two CeCoIn5 crystal platelets; the meander line itself is made from ordinary varnish-insulated Cu wire, 0.1 mm in diameter.

We have carried out a microwave study of single-crystal CeCoIn5, a

heavy-fermion material with a relatively high transition temperature, with the aim to study the spectrum of Order Parameter Collective Modes (OPCM).

Normalized transmitted signal vs. temperature for the frequencies 2932, 5852, 6912, 8501, 9004, 10288, 15478, and 16194 MHz (curves from 1 to 8, respectively).

We have discovered a rather abrupt change in the character of the transmitted signal vs. temperature dependence at frequencies in the vicinity of 9 GHz, implying an increased absorption at higher frequencies. This corresponds to the opening of a new “dissipation channel” in CeCoIn5 at an energy in the range 35-40 eV.

We are currently performing tunneling experiments to study pairing symmetry in CeCoIn5.

Collaborative Research: Collective Mode Spectroscopy in Unconventional Superconductors

John B. Ketterson, Northwestern University, DMR 0509357