10 June 2015 International review on Solid State Physics

Philipp Hauke explains non-standard Hubbard models

An in-depth review on non-standard Hubbard models in Reviews on Progress in Physics A team of researchers from Innsbruck, Barcelona, Warsaw, Krakow, Hamburg and Tel Aviv have come together to discuss and review the accomplishments achieved so far in the field of quantum physics concerning non-standard Hubbard models in optical lattices, all comprised in the work “Non-standard Hubbard models in optical lattices: a review” recently published in Reviews on Progress in Physics.

Ten years ago, optical lattices became a boom in the field of Atomic, Molecular and Optical physics. Optical lattices are intensity patterns formed by the interference of counter-propagating laser beams, in which the standing wave of light, traps atoms in their minimum energy stages or “sites”. The resulting arrangement of trapped atoms resembles a crystal lattice. Such systems may serve as quantum simulators of models known and studied in other areas of physics such as condensed matter and solid state physics.

Standard Hubbard models describe two effects that occur in optical lattices: firstly, atoms can tunnel from one site to the next and, secondly, when atoms meet they can interact with each other. Now, in this work, the researchers discuss briefly common models for mixtures, known as extended Bose–Hubbard models that include different types of interactions between neighboring sites, next-neighbor sites, and so on. They provide a review of these non-standard models concerning, among others, strong dipolar interactions between neighboring sites, where atoms feel each other’s presence at distance, strong contact interactions, where atoms tunnel in pairs, as well as density dependent tunnelling, where atoms tunnel to higher atoms density sites.

The article is an outstanding in-depth review about what is occurring in the world of theoretical and experimental quantum physics. It examines the new experiments that are currently being carried out, explores possible scenarios that involve different new exotic quantum phases that could occur in optical lattices, and puts forward the open problems that need to be addressed in the future.

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