Charge Density Wave Melting in One-Dimensional Wires with Femtosecond Subgap Excitation

Area of Science:

• Condensed Matter Physics
• Materials Science
• Ultrafast Spectroscopy

Background:

• Charge density waves (CDWs) are prevalent in low-dimensional metals, arising from electron-electron and electron-phonon interactions.
• Photodoping with femtosecond lasers can melt CDWs, inducing insulator-to-metal transitions, typically studied using above-gap excitation.

Purpose of the Study:

• Investigate charge density wave dynamics under subgap excitation using strong-field mid-infrared pulses.
• Explore the mechanism of CDW melting and subsequent electronic structure evolution.
• Characterize the timescale of these nonequilibrium phenomena.

Main Methods:

• Excitation of one-dimensional indium wires with a CDW gap using mid-infrared pulses (ℏω=190 meV) at megavolt per centimeter field strengths.
• Probing transient electronic structure with time- and angle-resolved photoemission spectroscopy (TR-ARPES).

Main Results:

• The CDW gap is filled on a timescale faster than 300 fs.
• Significant changes in the electronic band structure are observed within approximately 1 ps.
• The observed phenomena are attributed to multiphoton absorption across the CDW gap.

Conclusions:

• Subgap excitation with strong mid-infrared fields can effectively melt charge density waves.
• Multiphoton absorption is identified as the key mechanism driving the ultrafast insulator-to-metal transition in this regime.
• This work opens new avenues for studying CDW dynamics using subgap excitation.