Hyperbolic phonon-polariton electroluminescence in 2D heterostructures

Area of Science:

• Condensed Matter Physics
• Optoelectronics
• Materials Science

Background:

• Phonon polaritons couple photons and optical phonons in polar dielectrics, enabling subwavelength light confinement for applications like imaging and energy transfer.
• Conventional optical excitation methods for phonon polaritons are inefficient due to momentum mismatch and require costly setups.
• Existing techniques often involve complex near-field schemes, limiting practical applications.

Purpose of the Study:

• To demonstrate a novel, all-electrical method for exciting phonon polaritons.
• To investigate the feasibility of using drifting charge carriers to generate phonon polaritons.
• To explore the potential for electrically pumped light sources based on phonon polaritons.

Main Methods:

• Fabrication of hexagonal boron nitride (hBN)/graphene heterostructures.
• Electrically driving charge carriers in ultrahigh-mobility graphene out of equilibrium.
• Observation and analysis of mid-infrared electroluminescence from hBN's hyperbolic phonon polaritons (HPhPs).

Main Results:

• Achieved bright electroluminescence of HPhPs in hBN/graphene heterostructures via electrical excitation.
• Observed temperature and carrier density dependencies distinct from black-body thermal emission.
• Identified HPhP electroluminescence originating from both interband transitions and intraband Cherenkov radiation of charge carriers.

Conclusions:

• Phonon polaritons can be efficiently excited all-electrically by drifting charge carriers under specific conditions.
• This electrical excitation method overcomes the limitations of traditional optical approaches.
• The findings pave the way for developing electrically pumped mid-infrared and terahertz phonon-polariton light sources.