Chinese scholars have made new breakthroughs in the field of "atomic Lego" quantum simulation

Figure Quantum pseudocriticality
under strong horizontal magnetic fields.

With the support of the National Natural Science Foundation of China (approval number: 62034004, 62122036), Professor Miao Feng and collaborators of Nanjing University observed for the first time a special electron crystal state nailed to the Moore superlattice through the "atomic Lego" method
。 The study, titled "Tunable quantum criticalities in an isospin extended Hubbard model simulator," was published online in the journal Nature on September 14, 2022
.

The huge electron coulomb interactions in strongly correlated systems can induce the generation of rich and exotic quantum multibody states, including unconventional superconductivity, mott insulators, Wigner crystal states, non-Fermi liquids, quantum spin liquids, and so on
.

In order to capture the core physics of associative action, physicists abstracted several models from many-body systems, the most famous of which was the Hubbard model and the extended Hubbard model when considering long-range Coulomb effects
.

In the face of the above opportunities and challenges, Professor Miao Feng of Nanjing University cooperated with the team to build the SU(4) isospinner-extended Hubbard model quantum simulator based on the corner graphene molar superlattice system through the "atomic Lego" method, and for the first time observed a special electron crystal state nailed to the Moore superlattice: generalized isospin Wigner crystal
。 In the experiment, the research team achieved the quantum melting of the electron crystal through the in-situ regulation of the electron correlation strength by the vertical electric field, and observed the "quantum two-stage criticality
" for the first time 。 Based on the decoupled energy valley degrees of freedom and spin degrees of freedom in this system, the research team further realized the continuous evolution of the internal degrees of freedom of the extended Hubbard model quantum simulator from SU(4) to SU(2) by in situ adjustment of the horizontal magnetic field, and observed the "quantum pseudo criticality" (figure)
for the first time under high magnetic fields.

The "Atomic Lego" quantum simulator successfully simulates the in situ evolution from quantum phase transitions with critical intermediate phases in highly symmetric SU(4) strongly correlated electronic systems to weak first-order quantum phase transitions in low-symmetric SU(2) electronic systems, which not only makes it possible to simulate and deeply understand strongly correlated electronic systems with adjustable internal degrees of freedom, but also takes an important step
for the future development of solid-state quantum simulators that can be highly intensively integrated, highly adjustable and easy to read.