Electronic fine structure in the electron-hole plasma in SrB6

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Physics

Background:

• Alkaline earth hexaborides display unique electronic properties due to electron-hole mixing.
• Doped compounds like Ca1-xLaxB6 exhibit ferromagnetism with high Curie temperatures.
• Theoretical models suggest a potential for excitonic instability in these materials.

Purpose of the Study:

• To investigate the electronic state and magnetic behavior of strontium boride (SrB6).
• To compare the properties of SrB6 with doped alkaline earth hexaborides.
• To determine if SrB6 undergoes an excitonic condensation at low temperatures.

Main Methods:

• Analysis of Fermi surfaces and spectral distributions.
• Experimental data from de Haas-van Alphen, optical, transport, and tunneling measurements.
• Comparison with theoretical predictions for excitonic instability.

Main Results:

• SrB6 maintains its fermionic semimetal state down to at least 5 K.
• Evidence does not support the formation of an excitonic condensate in SrB6.
• Doped systems show a Curie temperature exceeding the degeneracy temperature.

Conclusions:

• Electron-hole mixing in SrB6 does not lead to an excitonic condensate under experimental conditions.
• SrB6 behaves as a conventional semimetal at low temperatures.
• The magnetic properties of doped hexaborides are distinct from the electronic state of undoped SrB6.