Isostructural electronic transition in MoS₂ probed by solid-state high-harmonic generation spectroscopy

Area of Science:

• Condensed matter physics
• Materials science
• Spectroscopy

Background:

• Studying materials under extreme pressure using diamond anvil cells (DACs) is crucial for discovering new states of matter.
• Direct measurement of electronic structure within DACs remains a significant challenge.
• Solid-state high-harmonic generation (sHHG) provides an all-optical method to probe material electronic structures.

Purpose of the Study:

• To demonstrate the capability of sHHG spectroscopy for probing electronic structure under high pressure within a DAC.
• To investigate pressure-induced electronic transitions in 2H-molybdenum disulfide (MoS2).

Main Methods:

• Utilized solid-state high-harmonic generation (sHHG) spectroscopy.
• Employed diamond anvil cells (DACs) to achieve pressures up to 30 GPa.
• Performed first-principles simulations to interpret experimental observations.

Main Results:

• Observed a pressure-induced crossover of the lowest direct bandgap in 2H-MoS2 from the K-point to the [Formula: see text]-point.
• Detected a sharp minimum in harmonic intensity and a 30° rotation of sHHG polarization anisotropy.
• Confirmed these electronic transitions occurred without a structural phase change.

Conclusions:

• sHHG spectroscopy is established as a sensitive probe for electronic transitions at high pressures.
• This technique enables the study of quantum phenomena previously inaccessible with conventional methods.
• The findings provide new insights into the electronic behavior of materials under extreme conditions.