Electrical Detection of Ultrastrong Coherent Interaction between Terahertz Fields and Electrons Using Quantum Point...

Area of Science:

• Quantum optics
• Condensed matter physics
• Nanotechnology

Background:

• Light-matter interaction in the ultrastrong coupling regime is crucial for coherent control of material properties.
• Electrical access to ultrastrongly coupled systems remains a significant challenge.
• Terahertz (THz) split-ring resonators (SRRs) are key components in exploring these interactions.

Purpose of the Study:

• To develop a method for electrical access to ultrastrongly coupled systems.
• To investigate light-matter interactions using a quantum point contact (QPC) and THz-SRR.
• To demonstrate coherent control of quantum phenomena via electrical and optical means.

Main Methods:

• Fabrication of a gate-defined QPC adjacent to a THz-SRR on a GaAs two-dimensional (2D) electron system.
• Illumination of the system with external THz radiation.
• Measurement of photocurrent spectra and QPC conductance under varying conditions.

Main Results:

• Observation of significant anticrossing in the photocurrent spectrum due to coupling between 2D electron cyclotron resonance and the SRR.
• Explanation of photocurrent via energy-selective transmission/reflection of quantum Hall edge channels at the QPC.
• Detection of anomalous conductance modulation in the QPC even in the absence of THz radiation.

Conclusions:

• The fabricated QPC-SRR system provides a viable platform for electrical access to ultrastrong coupling regimes.
• The observed phenomena demonstrate the potential for coherent control of quantum states using THz fields.
• This work opens new avenues for exploring fundamental light-matter interactions and developing novel quantum devices.