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Tetragonal-to-orthorhombic structural phase transition at 90 K in the superconductor Fe(1.01)Se
T M McQueen1, A J Williams, P W Stephens
1Department of Chemistry, Princeton University, Princeton New Jersey 08544, USA.
Physical Review Letters
|October 2, 2009
Summary
Superconducting iron selenide (FeSe) exhibits a structural transition at 90 K, unlike its nonsuperconducting counterpart. Magnetism does not drive this phase transition in the superconducting FeSe.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Solid State Chemistry
Background:
- Iron selenide (FeSe) is a superconductor with complex phase behavior.
- Understanding the relationship between crystal structure, superconductivity, and magnetism in FeSe is crucial.
- Previous studies have indicated structural transitions in FeSe, but detailed characterization remains ongoing.
Purpose of the Study:
- To investigate the structural transitions in superconducting Fe(1.01)Se and nonsuperconducting Fe(1.03)Se.
- To explore the atomic-level structural modulations in both superconducting and nonsuperconducting FeSe phases.
- To determine the role of magnetism in the phase transition of superconducting FeSe.
Main Methods:
- Temperature-dependent X-ray diffraction to identify structural phase transitions.
- High-resolution electron microscopy for atomic-scale structural analysis at low temperatures.
- Magnetic susceptibility measurements to probe magnetic ordering.
Main Results:
- Superconducting Fe(1.01)Se undergoes a tetragonal to orthorhombic structural transition at 90 K.
- Nonsuperconducting Fe(1.03)Se does not exhibit this specific structural transition.
- High-resolution electron microscopy revealed unexpected Fe atom displacements and complex nanometer-scale modulations in both superconducting and nonsuperconducting FeSe.
- Magnetism was found not to be the driving force for the phase transition in superconducting FeSe.
Conclusions:
- The structural transition at 90 K is intrinsically linked to the superconducting properties of FeSe.
- Complex structural modulations, beyond simple phase transitions, occur at the atomic and nanoscale in FeSe.
- Superconductivity in FeSe is not driven by magnetic ordering, suggesting other electronic mechanisms are at play.
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