Towards tunable quantum criticality in InAs quantum wells: hybrid metal-semiconductor quantum dots for charge Kondo effects*

Tunable quantum phase transitions based on the multichannel[1] and multi-island[2] charge Kondo effect has provided access to non-Fermi liquid quantum critical points. Work to date has been based on GaAs heterostructures, contacted by few-micron-size annealed metal islands. The large island size has limited studies to electron temperatures of 50 mK and below. The surface Fermi-level pinning in InAs affords direct ohmic contact to non-annealed sub-micron islands with large charging energies (E_c), offering the possibility of measurement over a 10x broader temperature range. We have demonstrated highly transparent interfaces (>99%) between quantum Hall edge states and sub-micron ohmic islands, and clean gate-defined constrictions in an InAs quantum well grown on InP. These building blocks enable the design of hybrid InAs/metal islands -- and arrays of effectively identical islands -- for simulating quantum criticality and gaining insight into Kondo lattice coherence.

  

[1] Iftikhar, Z. et al. Tunable quantum criticality and super-ballistic transport in a “charge” Kondo circuit. Science 360, 1315–1320 (2018).

[2] Pouse, W. et al. Exotic quantum critical point in a two-site charge Kondo circuit. arXiv:2108.12691 (2021).