Observation of phonon Stark effect

Area of Science:

• Condensed matter physics
• Quantum technologies
• Materials science

Background:

• The Stark effect, analogous to the Zeeman effect, is crucial in physics and technology.
• Its manifestation in collective excitations beyond excitons, like phonons, remains largely unexplored.
• Bilayer 2H-molybdenum disulfide (MoS2) is a promising two-dimensional quantum system.

Purpose of the Study:

• To investigate the existence and characteristics of the phonon Stark effect in bilayer 2H-MoS2.
• To understand the underlying mechanisms driving the observed effects.
• To explore the potential for phonon engineering through electric-field manipulation.

Main Methods:

• Experimental observation of phonon behavior under applied electric fields.
• Spectroscopic analysis to measure phonon frequency shifts.
• Many-body ab initio calculations to model electron-phonon interactions.

Main Results:

• Observation of a giant phonon Stark effect in bilayer 2H-MoS2, with linear red-shift of longitudinal acoustic phonons (~1 THz tuning).
• Identification of strong coupling between phonons and interlayer excitons (IXs) as the fundamental origin.
• Discovery of IX-mediated electro-phonon intensity modulation exceeding 1200% for the A2u phonon.

Conclusions:

• The study confirms the exotic phonon Stark effect in a 2D quantum system.
• Interlayer excitons mediate effective phonon engineering via electric fields.
• Findings offer potential for novel many-body physics and technological innovations.