Evidence for an Electronically Driven Charge Density Wave in a 1D Metallic MOF

Area of Science:

• Materials Science
• Condensed Matter Physics
• Crystallography

Background:

• Charge density wave (CDW) phases are unconventional quantum states typically found in low-dimensional metallic systems.
• Their presence in porous materials is exceptionally rare, with LnHOTP metal-organic frameworks (MOFs) being the sole proposed example based on structural modulation.
• The electronic origin versus a purely structural nature of this modulation remained undetermined.

Purpose of the Study:

• To investigate the origin of the structural modulation in LnHOTP MOFs.
• To determine if the observed modulation is indicative of a charge density wave (CDW) phase with electronic origins.
• To explore the influence of pressure on the CDW phase in these porous materials.

Main Methods:

• Low-temperature and high-pressure crystallography were employed.
• Structural analysis was performed on a series of LnHOTP MOFs (Ln = La, Ce, Pr, Nd, Sm).
• The wavevector (q) characterizing the modulation was measured under varying pressure conditions.

Main Results:

• Evidence for an electronic origin of the CDW phase was established in LnHOTP MOFs.
• The modulation was shown to influence the relative rotation of neighboring HOTP ligands.
• The wavevector magnitude (q) demonstrated pressure sensitivity and exhibited commensurability lock-in at q = 1/3 c.

Conclusions:

• The study provides key evidence for the energetic stabilization of the CDW phase in LnHOTP MOFs.
• The findings confirm the electronic nature of the modulation, distinguishing it from a trivial structural effect.
• This work advances the understanding of exotic quantum phenomena in porous materials.