Hybrid quantum dots for quantum simulation of Kondo lattice models

08/08/2023, 2:45pm-3:00pm
Presenter: Praveen Sriram

Simplified effective Hamiltonians are key to understanding the behavior of quantum many-body systems, however, even relatively simple models often defy computational treatment on the fastest classical supercomputers. This has prompted the development of several quantum simulation platforms, each with a distinctive set of advantages. The use of ultracold atom arrays to model electrons in a bulk crystal has seen tremendous progress, but explorations of quantum phase transitions has been limited by the difficulty in cooling down to a many-body ground state. Few-site semiconductor quantum dot arrays implement a lattice of “artificial atoms” in a reservoir of mobile electrons, and have provided controllable realizations of diverse ground state phenomena. However, intersite inhomogeneity presents a major roadblock to scaling and tuning larger arrays. A new paradigm for quantum simulation is based on quantum dots formed from a hybrid metal-semiconductor island. The quasi-continuous level spectrum of the metallic component screens out differences between similarly patterned islands – enabling an array of sites to behave essentially identically, while the semiconductor retains tunability of intersite coupling through electrostatic gating, providing a scalable platform for simulating strong interactions. Recent work on a pair of hybrid metal-GaAs dots investigated a novel non-Fermi liquid critical point based on Kondo interactions mediated by the charge of the metallic island[1]. The islands had to be a few microns wide, given how ohmic contacts are made to GaAs. The surface Fermi level pinning in InAs provides a pathway for designing submicron hybrid dots with larger charging energy, enabling investigations of critical scaling over a broader temperature range. We have demonstrated the essential building blocks in an InAs quantum well – clean quantum point contacts[2], highly transparent transmission (>99%) of 1D modes into submicron metal islands, and tunable hybrid metal-InAs dots – for building sizable arrays to gain insights into the Kondo lattice coherence in heavy-fermion materials.

1. Pouse, W. et al. Nat. Phys. (2023)
2. Hsueh, C.L., Sriram, P. et al. Phys. Rev. B 105, 195303 (2022)