Design and construction of a point-contact spectroscopy rig with lateral scanning capability

TL;DR

This paper presents a versatile cryogenic rig with lateral scanning for point-contact spectroscopy, enabling in situ probing, phase-sensitive measurements, and compatibility with various cryostats, demonstrated through Nb film tests.

Contribution

The paper introduces a novel cryogenic rig with integrated nano-positioners and multiple functionalities for advanced point-contact spectroscopy measurements.

Findings

Successful in situ probing of samples in different regions.

Capability to form double point-contacts for interferometry.

Effective performance demonstrated in Nb thin film measurements.

Abstract

The design and realization of a cryogenic rig for point-contact spectroscopy measurements in the needle-anvil configuration is presented. Thanks to the use of two piezoelectric nano-positioners, the tip can move along the vertical ($z$) and horizontal ($x$) direction and thus the rig is suitable to probe different regions of a sample \textit{in situ}. Moreover, it can also form double point-contacts on different facets of a single crystal for achieving, e.g., an interferometer configuration for phase-sensitive measurements. For the latter purpose, the sample holder can also host a Helmholtz coil for applying a small transverse magnetic field to the junction. A semi-rigid coaxial cable can be easily added for studying the behavior of Josephson junctions under microwave irradiation. The rig can be detached from the probe and thus used with different cryostats. The performance of this new probe has been tested in a Quantum Design PPMS system by conducting point-contact Andreev reflection measurements on Nb thin films over large areas as a function of temperature and magnetic field.