Microstructuring YbRh2Si2 for resistance and noise measurements down to ultra-low temperatures

Alexander Steppke*, Sandra Hamann, Markus König, Andrew P Mackenzie, Kristin Kliemt, Cornelius Krellner, Marvin Kopp, Martin Lonsky, Jens Müller, Lev V Levitin, John Saunders, Manuel Brando*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

The discovery of superconductivity in the quantum critical Kondo-lattice system YbRh2Si2 at an extremely low temperature of 2 mK has inspired efforts to perform high-resolution electrical resistivity measurements down to this temperature range in highly conductive materials. Here we show that control over the sample geometry by microstructuring using focused-ion-beam techniques allows to reach ultra-low temperatures and increase signal-to-noise ratios (SNRs) tenfold, without adverse effects to sample quality. In five experiments we show four-terminal sensing resistance and magnetoresistance measurements which exhibit sharp phase transitions at the Néel temperature, and Shubnikov–de-Haas (SdH) oscillations between 13 T and 18 T where we identified a new SdH frequency of 0.39 kT. The increased SNR allowed resistance fluctuation (noise) spectroscopy that would not be possible for bulk crystals, and confirmed intrinsic 1/f -type fluctuations. Under controlled strain, two thin microstructured samples exhibited a large increase of TN from 67 mK up to 188 mK while still showing clear signatures of the phase transition and SdH oscillations. Superconducting quantum interference device-based thermal noise spectroscopy measurements in a nuclear demagnetization refrigerator down to 0.95 mK, show a sharp superconducting transition at Tc=1.2 mK. These experiments demonstrate microstructuring as a powerful tool to investigate the resistance and the noise spectrum of highly conductive correlated metals over wide temperature ranges.
Original languageEnglish
Article number123033
Number of pages14
JournalNew Journal of Physics
Volume24
Issue number12
DOIs
Publication statusPublished - 29 Dec 2022

Keywords

  • Strongly correlated electron systems
  • Heavy fermions
  • Electrical and thermal conduction in crystalline metals and alloys
  • Fluctuation phenomena
  • Random processes
  • Noise
  • Brownian motion

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