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arXiv · 2604.03821

A Top-Loading Point-Contact Spectroscopy Probe with In-Situ Sample Exchange for Dilution Refrigerators

Ghulam Mohmad·Atanu Mishra·Goutam Sheet
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Abstract

We report the design and implementation of a point-contact spectroscopy (PCS) system integrated with a dilution refrigerator, enabling measurements down to 30 mK. The setup employs a needle-anvil geometry with a cryogenic piezo-driven nanopositioner for in-situ formation of mesoscopic point contacts. We discuss the thermal anchoring strategies that enable efficient cooling of the probe to ultra-low temperatures and reliable measurements. We also address positioner-related challenges and the solutions implemented to ensure stable operation at millikelvin temperatures. The performance of the probe is demonstrated through point contact spectroscopy on Ta-doped TiSe$_2$ (Ta$_x$Ti$_{1-x}$Se$_2$, $x = 0.2$), a superconductor with $T_c \approx 2.3$ K. The spectra exhibit well-defined superconducting features that systematically diminish with increasing temperature and magnetic field. The platform provides a robust and versatile tool for spectroscopic investigations of superconductors and other quantum materials at millikelvin temperatures and high magnetic fields.

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Ghulam Mohmad, Atanu Mishra, Goutam Sheet. 2026-04-04. A Top-Loading Point-Contact Spectroscopy Probe with In-Situ Sample Exchange for Dilution Refrigerators. https://arxiv.org/abs/2604.03821

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