Spin-Imbalance In A 2d Fermi-Hubbard System, Peter T. Brown, Debayan Mitra, Elmer Guardado-Sanchez, Peter Schauß, Stanimir S. Kondov, Ehsan Khatami, Thereza Paiva, Nandini Trivedi, David A. Huse, Waseem S. Bakr
Sep 2017

#### Spin-Imbalance In A 2d Fermi-Hubbard System, Peter T. Brown, Debayan Mitra, Elmer Guardado-Sanchez, Peter Schauß, Stanimir S. Kondov, Ehsan Khatami, Thereza Paiva, Nandini Trivedi, David A. Huse, Waseem S. Bakr

*Ehsan Khatami*

The interplay of strong interactions and magnetic fields gives rise to unusual forms of superconductivity and magnetism in quantum many-body systems. Here, we present an experimental study of the two-dimensional Fermi-Hubbard model—a paradigm for strongly correlated fermions on a lattice—in the presence of a Zeeman field and varying doping. Using site-resolved measurements, we revealed anisotropic antiferromagnetic correlations, a precursor to long-range canted order. We observed nonmonotonic behavior of the local polarization with doping for strong interactions, which we attribute to the evolution from an antiferromagnetic insulator to a metallic phase. Our results pave the way to experimentally mapping ...

Machine Learning Phases Of Strongly Correlated Fermions, Kelvin Ch'ng, Juan Carrasquilla, Roger G. Melko, Ehsan Khatami
Aug 2017

#### Machine Learning Phases Of Strongly Correlated Fermions, Kelvin Ch'ng, Juan Carrasquilla, Roger G. Melko, Ehsan Khatami

*Ehsan Khatami*

Machine learning offers an unprecedented perspective for the problem of classifying phases in condensed matter physics. We employ neural network machine learning techniques to distinguish finite-temperature phases of the strongly-correlated fermions on cubic lattices. We show that a three-dimensional convolutional network trained on auxiliary field configurations produced by quantum Monte Carlo simulations of the Hubbard model can correctly predict the magnetic phase diagram of the model at the average density of one (half filling). We then use the network, trained at half filling, to explore the trend in the transition temperature as the system is doped away from half filling ...

Competing Phases And Orbital-Selective Behaviors In The Two-Orbital Hubbard-Holstein Model, Shaozhi Li, Ehsan Khatami, Steven Johnston
Mar 2017

#### Competing Phases And Orbital-Selective Behaviors In The Two-Orbital Hubbard-Holstein Model, Shaozhi Li, Ehsan Khatami, Steven Johnston

*Ehsan Khatami*

We study the interplay between the electron-electron (*e-e*) and the electron-phonon (*e-ph*) interactions in the two-orbital Hubbard-Holstein model at half-filling using the dynamical mean-field theory. We find that the *e-ph* interaction, even at weak couplings, strongly modifies the phase diagram of this model and introduces an orbital-selective Peierls insulating phase (OSPI) that is analogous to the widely studied orbital-selective Mott phase (OSMP). At small *e-e* and *e-ph* couplings, we find a competition between the OSMP and the OSPI, while at large couplings, a competition occurs between Mott and charge-density-wave (CDW) insulating phases. We further demonstrate that the Hund's coupling ...

Competing Phases And Orbital-Selective Behaviors In The Two-Orbital Hubbard-Holstein Model, Shaozhi Li, Ehsan Khatami, Steven Johnston
Dec 2016

#### Competing Phases And Orbital-Selective Behaviors In The Two-Orbital Hubbard-Holstein Model, Shaozhi Li, Ehsan Khatami, Steven Johnston

*Ehsan Khatami*

We study the interplay between the electron-electron (e-e) and the electron-phonon (e-ph) interactions in the two-orbital Hubbard-Holstein model at half filling using the dynamical mean field theory. We find that the e-ph interaction, even at weak couplings, strongly modifies the phase diagram of this model and introduces an orbital-selective Peierls insulating phase (OSPI) that is analogous to the widely studied orbital-selective Mott phase (OSMP). At small e-e and e-ph coupling, we find a competition between the OSMP and the OSPI, while at large couplings, a competition occurs between Mott and charge-density-wave (CDW) insulating phases. We further demonstrate that the Hund ...