3He physics
Fyzika 3He

Micro and nano resonators

We introduce and present a method of preparation and preliminary vacuum measurements conducted at temperature of 20 mK of a new typ of micro-resonator based on Sn-whiskers. Sn-whiskers have approximatelly 1 µm radius and their length can be up to 3 mm. As added benefit, the Sn-whiskers are mono-crystalline metal fibers with relatively smooth surface and being superconducting at low temperatures one may expect their high Q-factors.

The SEM picture of the Sn-whisker mounted and electrically connected to two copper wires of 50 µm diameter by a silver conductive epoxy. Inset hows both details of the Sn-whisker surface and the silver epoxy.

Figure below shows clear transitions into superconducting state of two samples of Snwhiskers. The transitions occurred at temperature of 3 K, which corresponds to the transition temperature of beta-tin into superconducting state.

The phase transitions of two samples of Sn-whiskers into superconducting state. The non-zero residual resistance is due to the contact resistance of silver conductive epoxy used for whisker attachment. Inset hows SAED analysis from TEM of one of the samples confirming the beta-phase of Sn-whiskers.

Figure shows resonant characteristics of the Sn-whisker measured at three different driving forces and magnetic fields. Whisker‘s response measured at 100 mT with driving force 5 pN is highly non-linear demonstrating the properties of a “Duffing” oscillator.

The resonant characteristics of Sn-whisker measured at different magnetic fields and driving forces. 1: B = 50 mT, F = 2.5 pN, 2: B = 100 mT, F = 2.0 pN, and 3: B = 100 mT, F = 5.0 pN. In order to display these characteristics DC offset of measured signal was altered. Inset shows both measured signals: absorption and dispersion for condition 2.

M. Človečko, E. Gažo, S. Longauer, E. Múdra, et al.
Vacuum Measurements of a Novel Micro-resonator Based on Tin Whiskers Performed at mK Temperatures,
JLTP 175 449-455 (2014).

We have introduced a technique of preparation of the Al-nano bridges. These structures are going to be studied in nearest future.