Rolled-up superconducting niobium nano-coils

Date

Jun 7, 2017

Time

10:00 AM - 11:00 AM

Speaker

Sören Lösch

Affiliation

IFW Dresden

Language

en

Main Topic

Materialien

Other Topics

Materialien, Physik

Host

Kristina Krummer-Meier

Description

Superconductors as bulk materials and (structured) thin films on substrates of high thermal conductivity (e.g. Si, GaAs) show a continuous transition[1] of the resistance from the superconducting (0 ohm) to normal state (>0 ohm) if one increases one of the parameters: temperature, magnetic field or applied current over a critical value. In the fabricated rolled-up superconducting nano-coils this behaviour dramatically changes. We observe a broad transition interval where the nano-coil switches between the superconducting and a resistive state before it reaches the normal state (Fig. 1). The coils with diameters of a few micrometers (Fig. 2) have been fabricated by rolled-up technology. The method requires standard twodimensional lithography techniques and etching processes. It is based on a molecular beam epitaxy grown anisotropic strained bi-layer system GaAs/InGaAs[2]. A superconducting niobium layer has been deposited via conventional deposition techniques on the MBE-grown strained layer system. The resistance jumps within a broad interval indicate that the fabricated thin superconducting structures are thermally decoupled from the substrate and therefore react very sensitively on small changes of external physical factors. This may provide an application as transition-edge-sensor bolometer for detection of emradiation in the range from several 100 GHz up to a few THz[3]. Transition edge sensors are the state-of-the-art technology in cosmic microwave background measurements[4]. A rough calculation shows, that our nano-coil is a promising candidate to achieve higher sensitivity then the existing spider-web-bolometers[3,4] because of thin layer Technology used to fabricate and operating in vacuum. We performed comparative transport measurements between nano-coils, embedded nano-coils, freestanding planar stripes (bridges) and planar stripes on different substrates (GaAs and fused silica). Main focus has been the different thermal contacts between superconducting niobium and the environment. Possible theoretical explanations of this phenomenon will be given.

Links

• Seminars at the IFW

Last modified: Jun 7, 2017, 9:54:32 AM