Valley-Polarized Quantum Hall Phase in a Strain-Controlled Dirac System.

Area of Science:

• Condensed matter physics
• Materials science
• Spintronics

Background:

• Multivalley systems exhibit rich physics related to valley pseudospin, enabling applications like valleytronics.
• Strain engineering is a powerful tool for tuning electronic properties and exploring novel quantum phases.

Purpose of the Study:

• To investigate the impact of strain engineering on the quantum Hall effect in Pb_{1-x}Sn_{x}Se Dirac systems.
• To explore the emergence of new quantum phases driven by changes in valley degeneracy.

Main Methods:

• Utilizing strain engineering to modify the electronic band structure of Pb_{1-x}Sn_{x}Se.
• Observing and characterizing quantum Hall phases through transport measurements.

Main Results:

• Achieved fully valley-polarized quantum Hall phases in the studied system.
• Observed a unique "bipolar quantum Hall phase" when valley energy splitting surpassed the band gap.
• Demonstrated the coexistence of hole and electron chiral edge states at distinct valleys within the same quantum well.

Conclusions:

• Strain engineering effectively controls valley polarization in Pb_{1-x}Sn_{x}Se.
• The bipolar quantum Hall phase highlights novel phenomena arising from valley manipulation.
• Coexisting chiral edge states from different valleys do not exhibit destructive interference, opening possibilities for complex electronic devices.