Friday Quantum Seminar

In this talk, I will present a theory of interaction-induced band-flattening in strongly correlated electron systems. I will begin by illustrating an inherent connection between flat bands and index theorems and presenting a generic prescription for constructing flat bands by periodically repeating local Hamiltonians with topological zero modes. Specifically, a Dirac particle in an external, spatially periodic magnetic field can be cast in this form.

Abstract: In this talk, I will present a theory of interaction-induced band-flattening in strongly correlated electron systems. I will begin by illustrating an inherent connection between flat bands and index theorems and presenting a generic prescription for constructing flat bands by periodically repeating local Hamiltonians with topological zero modes. Specifically, a Dirac particle in an external, spatially periodic magnetic field can be cast in this form.

Optical experiments utilize excitons (electron-hole bound states) in moir ́e transition metal dichalcogenide bilayers as a quantum simulator of the Bose-Hubbard model. Nevertheless, we show that these excitations possess nonbosonic commutation relations due to their composite nature, limiting the size of phase space for them to occupy. Such an effect manifests at weak electron-hole correlation, and restricts the number of excitons to be less than 4 per site and valley for three different bilayers.

Abstract: Optical experiments utilize excitons (electron-hole bound states) in moiré transition metal dichalcogenide bilayers as a quantum simulator of the Bose-Hubbard model. Nevertheless, we show that these excitations possess nonbosonic commutation relations due to their composite nature, limiting the size of phase space for them to occupy. Such an effect manifests at weak electron-hole correlation, and restricts the number of excitons to be less than 4 per site and valley for three different bilayers.

Understanding the Hubbard model is crucial for investigating various quantum many-body states and its fermionic and bosonic versions have been largely realized separately. Recently, transition metal dichalcogenides heterobilayers have emerged as a promising platform for simulating the rich physics of the Hubbard model. In this work, we explore the interplay between fermionic and bosonic populations, using a WS2/WSe2 heterobilayer device that hosts this hybrid particle density.

A spontaneous symmetry-breaking order is conventionally described by a tensor-product wave-function of some few-body clusters. We discuss a type of symmetry-breaking orders, dubbed entanglement-enabled symmetry-breaking orders, which cannot be realized by any tensor-product state. Given a symmetry breaking pattern, we propose a criterion to diagnose if the symmetry-breaking order is entanglement-enabled, by examining the compatibility between the symmetries and the tensor-product description.

Strong light-matter coupling in optical cavities can alter the dynamics of molecular and material systems resulting in polaritonic excitation spectra and modified reaction pathways. For strongly coupled photon modes close in energy to nuclear vibrations the Cavity Born Oppenheimer Approximation (CBOA) in the context of quantum-electrodynamical density functional theory (QEDFT) has been demonstrated to be an appropriate description of the coupled light-matter system.

Abstract: Atom interferometers can be used to obtain information about accelerations and fields, whether this may be in the investigation of fundamental aspects of physics, such as measuring fundamental constants or testing gravity, or as part of a measurement device, such as an accelerometer [1,2,3]. Achieving adequate coherence times remains a priority, and this can be realized by holding the atoms in a trap as an alternative to increasing their free fall time [1].

Atom interferometers can be used to obtain information about accelerations and fields, whether this may be in the investigation of fundamental aspects of physics, such as measuring fundamental constants or testing gravity, or as part of a measurement device, such as an accelerometer [1,2,3]. Achieving adequate coherence times remains a priority, and this can be realized by holding the atoms in a trap as an alternative to increasing their free fall time [1].

(Pizza and refreshments will be served after the talk.)