Quantum simulation of the Mott transition in the Fermi-Hubbard model using gate-controlled semiconductor quantum-dot chains
Wen-Yao Wei1, Tung-Sheng Lo1, Kuan-Ting Lin4, Markus Brink3, Dah-Chin Ling2, Cheng-Chung Chi1, Chung-Yu Mou1, Jeng-Chung Chen1*, Dennis M. Newns3, Chang C. Tsuei3
1Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
2Department of Physics, Tamkang University, New Taipei City, Taiwan
3IBM Thomas J. Watson Research Center, NY, USA
4Department of Precision Engineering, The University of Tokyo, Tokyo, Japan
* presenting author:Jeng-Chung Chen, email:jcchen@phys.nthu.edu.tw
Landau Fermi-liquid theory represents a remarkably successful description of the electronic interaction in most condensed matter. Such a nearly free-electron approximation fails completely in dealing with Mott insulators, a class of large onsite-Coulomb-repulsion driven materials defying being a metal predicted by conventional band theory. Intriguing phenomena in high-Tc cuprate superconductors, one of the most challenging problems in the condensed matter physics, also underscore the importance of solving the quantum many-body problem at the microscopic level. Due to the exponential complexity involved, this is an impossible task without using a quantum computer, an amenity not available yet. The Hubbard model, even without including the long-range Coulomb interaction, can capture the essence of strong correlation effects such as the Mott insulator to metal transition. However, except in one dimension, it has no analytic solution to date. It has been shown that the Hamiltonian of a quantum dot array (QDA) can map onto that of a two-dimensional Fermi Hubbard model, which is widely used to mimic the strong Coulomb correlation in the CuO2 plane in cuprate superconductors. A simulation of the Hubbard model on a gate-controlled semiconductor quantum-dot linear chain would gain insight into the many-body physics. We present here direct evidence for Mott transition via a low-temperature (20 mK) electron transport study of a six-QD chain. Through a combined operation of two gate voltages, the inter-dot coupling can be fine-tuned continuously to enable the QDA conductance spectrum to undergo a localization to delocalization transition process which manifests as a collapse of collective Coulomb blockade. In addition, our bias voltage controlled conductance map allows us to use QDA as an on-chip laboratory for studying Mott physics. Our coupled QDA device provides a platform for developing engineered QD materials, qubit systems and artificial molecular devices.

Keywords: quantum simulator, quantum dot