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Nematic Crossover in BaFe(2)As(2) under Uniaxial Stress
Xiao Ren1, Lian Duan1, Yuwen Hu1
1International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.
Physical Review Letters
|November 21, 2015
Summary
Raman scattering reveals that applied stress in BaFe2As2 crystals alters structural transitions. Residual stress in unstressed samples may explain apparent symmetry breaking above the transition temperature.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Crystallography
Background:
- BaFe2As2 is the parent compound for "122" Fe-based superconductors.
- Studying symmetry breaking is crucial for understanding superconductivity.
- Raman scattering is a technique capable of detecting point-group symmetry breaking.
Purpose of the Study:
- To investigate the effects of applied stress on the structural phase transition of BaFe2As2.
- To determine the role of residual stress in observed phenomena above the transition temperature.
- To clarify the onset of spontaneous nematicity in BaFe2As2.
Main Methods:
- Utilizing Raman scattering to probe symmetry changes.
- Applying compression along the Fe-Fe direction in BaFe2As2 crystals.
- Analyzing structural phase transitions and residual stress distributions.
Main Results:
- Applied compression transforms the structural phase transition into a broad crossover.
- Significant residual stress exists even in unstressed BaFe2As2 crystals.
- Observed phenomena above T(s) can be attributed to residual stress.
Conclusions:
- Spontaneous nematicity in BaFe2As2 initiates only below the structural transition temperature T(s).
- Residual stress significantly influences the interpretation of structural transitions and symmetry breaking.
- Raman spectroscopy provides a powerful tool for studying stress-induced phenomena in materials.
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