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Nernst Sign Reversal in the Hexatic Vortex Phase of Weakly Disordered a-MoGe Thin Films
1Department of Physics and Jack and Pearl Resnick Institute and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel.
Physical Review Letters
|January 26, 2024
Summary
Researchers observed a surprising Nernst sign reversal during the hexatic phase melting transition in superconducting molybdenum germanium. This phenomenon is linked to vortex dislocations diffusing from colder to hotter regions.
Area of Science:
- Condensed matter physics
- Superconductivity
- 2D materials
Background:
- The hexatic phase is an intermediate state in the melting of 2D crystals, characterized by topological defects.
- This phase was recently identified in the vortex lattice of 2D weakly disordered superconducting molybdenum germanium (MoGe).
- Understanding the behavior of this exotic phase is crucial for advancing superconductivity research.
Purpose of the Study:
- To investigate the hexatic phase in superconducting MoGe using the Nernst effect.
- To explore vortex motion and its implications during the melting transition.
- To elucidate the underlying mechanisms responsible for observed phenomena.
Main Methods:
- Utilizing the Nernst effect, a sensitive probe for vortex motion, particularly in the superconducting fluctuation regime.
- Conducting measurements on 2D weakly disordered superconducting MoGe samples.
- Analyzing the vortex state and its response to thermal gradients.
Main Results:
- A surprising Nernst sign reversal was detected at the melting transition of the hexatic phase.
- The observed Nernst sign reversal is proposed to be a consequence of vortex dislocations.
- These dislocations appear to diffuse preferentially from colder to hotter regions within the hexatic state.
Conclusions:
- The Nernst effect provides valuable insights into the dynamics of the hexatic phase in superconductors.
- Vortex dislocations play a significant role in the observed Nernst sign reversal during hexatic phase melting.
- Further research into vortex dynamics can deepen our understanding of phase transitions in 2D superconducting systems.
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