Abstract
Quantum systems with engineered Hamiltonians can be used to study many-body physics problems to provide insights beyond the capabilities of classical computers. Semiconductor gate-defined quantum dot arrays have emerged as a versatile platform for realizing generalized Fermi-Hubbard physics, one of the richest playgrounds in condensed matter physics. In this work, we employ a germanium quantum dot array and show that the naturally occurring long-range Coulomb interaction can lead to exciton formation and transport. We tune the quantum dot ladder into two capacitively coupled channels and exploit Coulomb drag to probe the binding of electrons and holes. Specifically, we shuttle an electron through one leg of the ladder and observe that a hole is dragged along in the second leg under the right conditions. This corresponds to a transition from single-electron transport in one leg to exciton transport along the ladder. Our work paves the way for the study of excitonic states of matter in quantum dot arrays.
- Received 5 July 2023
- Revised 8 December 2023
- Accepted 5 February 2024
DOI:https://doi.org/10.1103/PhysRevX.14.011048
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Highly controllable quantum mechanical systems are attractive platforms for studying quantum many-body problems. Owing to their in situ tunability and intrinsic long-range Coulomb interaction, electrons or holes in semiconductor quantum dot arrays are natural choices for realizing various condensed-matter models. Here, we show the creation and motion of a bound electron-hole pair, or exciton, in a quantum dot ladder, making it a novel platform for studying excitonic physics.
We fabricate a quantum dot ladder on a germanium quantum well heterostructure. We first demonstrate the individual control of the charge occupation and of the charge hopping amplitudes across the array of dots. Then, by suppressing the hopping between the two legs, we engineer the system into a Coulomb-coupled ladder, in which one leg hosts an electron and the other hosts a hole. We observe exciton formation and exciton transport when the ladder favors an exciton ground state.
In the future, with sufficiently homogeneous exciton energies and exciton hopping amplitudes, it will be possible to observe interesting excitonic phenomena such as delocalized excitons, excitonic insulators, or even exciton quasicondensates.
