scholarly journals Spin transport in a Mott insulator of ultracold fermions

Science ◽  
2018 ◽  
Vol 363 (6425) ◽  
pp. 383-387 ◽  
Author(s):  
Matthew A. Nichols ◽  
Lawrence W. Cheuk ◽  
Melih Okan ◽  
Thomas R. Hartke ◽  
Enrique Mendez ◽  
...  
Keyword(s):  
Hubbard Model ◽  
Spin Transport ◽  
Spin Diffusion ◽  
Quantum Limit ◽  
Strong Interactions ◽  
Strongly Correlated ◽  
Strongly Correlated Materials ◽  
Fermionic Atoms ◽  
And Diffusion ◽  
Shed Light

Strongly correlated materials are expected to feature unconventional transport properties, such that charge, spin, and heat conduction are potentially independent probes of the dynamics. In contrast to charge transport, the measurement of spin transport in such materials is highly challenging. We observed spin conduction and diffusion in a system of ultracold fermionic atoms that realizes the half-filled Fermi-Hubbard model. For strong interactions, spin diffusion is driven by super-exchange and doublon-hole–assisted tunneling, and strongly violates the quantum limit of charge diffusion. The technique developed in this work can be extended to finite doping, which can shed light on the complex interplay between spin and charge in the Hubbard model.

scholarly journals Tuning bad metal and non-Fermi liquid behavior in a Mott material: Rare-earth nickelate thin films

2015 ◽  
Vol 1 (10) ◽  
pp. e1500797 ◽  
Author(s):  
Evgeny Mikheev ◽  
Adam J. Hauser ◽  
Burak Himmetoglu ◽  
Nelson E. Moreno ◽  
Anderson Janotti ◽  
...  
Keyword(s):  
Fermi Liquid ◽  
Epitaxial Films ◽  
Strongly Correlated ◽  
Complex Phase ◽  
Strongly Correlated Materials ◽  
Liquid Phases ◽  
Liquid Behavior ◽  
Novel Devices ◽  
Shed Light ◽  
Fermi Liquid Behavior

Resistances that exceed the Mott-Ioffe-Regel limit (known as bad metal behavior) and non-Fermi liquid behavior are ubiquitous features of the normal state of many strongly correlated materials. We establish the conditions that lead to bad metal and non-Fermi liquid phases in NdNiO3, which exhibits a prototype bandwidth-controlled metal-insulator transition. We show that resistance saturation is determined by the magnitude of Ni egorbital splitting, which can be tuned by strain in epitaxial films, causing the appearance of bad metal behavior under certain conditions. The results shed light on the nature of a crossover to a non-Fermi liquid metal phase and provide a predictive criterion for Anderson localization. They elucidate a seemingly complex phase behavior as a function of film strain and confinement and provide guidelines for orbital engineering and novel devices.

scholarly journals Strange metallicity in the doped Hubbard model

Science ◽  
2019 ◽  
Vol 366 (6468) ◽  
pp. 987-990 ◽  
Author(s):  
Edwin W. Huang ◽  
Ryan Sheppard ◽  
Brian Moritz ◽  
Thomas P. Devereaux
Keyword(s):  
Hubbard Model ◽  
Quantum Monte Carlo ◽  
High Temperature Superconductors ◽  
Linear Temperature Dependence ◽  
Strongly Correlated ◽  
Linear Temperature ◽  
Strongly Correlated Materials ◽  
Starting Point ◽  
Wide Range ◽  
Degenerate Regime

Strange or bad metallic transport, defined by incompatibility with the conventional quasiparticle picture, is a theme common to many strongly correlated materials, including high-temperature superconductors. The Hubbard model represents a minimal starting point for modeling strongly correlated systems. Here we demonstrate strange metallic transport in the doped two-dimensional Hubbard model using determinantal quantum Monte Carlo calculations. Over a wide range of doping, we observe resistivities exceeding the Mott-Ioffe-Regel limit with linear temperature dependence. The temperatures of our calculations extend to as low as 1/40 of the noninteracting bandwidth, placing our findings in the degenerate regime relevant to experimental observations of strange metallicity. Our results provide a foundation for connecting theories of strange metals to models of strongly correlated materials.

scholarly journals Spin-imbalance in a 2D Fermi-Hubbard system

Science ◽  
2017 ◽  
Vol 357 (6358) ◽  
pp. 1385-1388 ◽  
Author(s):  
Peter T. Brown ◽  
Debayan Mitra ◽  
Elmer Guardado-Sanchez ◽  
Peter Schauß ◽  
Stanimir S. Kondov ◽  
...  
Keyword(s):  
Hubbard Model ◽  
Metallic Phase ◽  
Strong Interactions ◽  
Temperature Phase ◽  
Strongly Correlated ◽  
Many Body ◽  
Open Questions ◽  
Antiferromagnetic Correlations ◽  
Strongly Correlated Fermions ◽  
Many Body Systems

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 the low-temperature phase diagram of the Fermi-Hubbard model as a function of both doping and spin polarization, for which many open questions remain.

scholarly journals Spin diffusion and spin conductivity in the two-dimensional Hubbard model

2021 ◽  
Vol 103 (15) ◽  
Author(s):  
Martin Ulaga ◽  
Jernej Mravlje ◽  
Jure Kokalj
Keyword(s):  
Hubbard Model ◽  
Spin Diffusion ◽  
Two Dimensional

scholarly journals Transmission and diffusion: Linguistic change in the regional French of Béarn

2015 ◽  
Vol 26 (3) ◽  
pp. 327-352
Author(s):  
DAMIEN MOONEY
Keyword(s):  
Individual Change ◽  
Vowel Quality ◽  
Linguistic Change ◽  
Local Varieties ◽  
Transmission Process ◽  
Non Local ◽  
Diffusion Interface ◽  
Successive Generations ◽  
And Diffusion ◽  
Shed Light

ABSTRACTThis article examines the seemingly dichotomous linguistic processes of transmission and diffusion (Labov, 2007) in the regional variety of French spoken in Béarn, southwestern France. Using a sociophonetic apparent time methodology, an analysis of nasal vowel quality provides evidence for the advancement of linguistic changes from below taking place between successive generations during the transmission process, as well as for change from above taking place in the variety as a result of exposure to diffusing non-local varieties of French. The results address Labov's (2007) assertion that it is rare to investigate incremental changes occurring from below in European dialectological studies and shed light on the transmission–diffusion interface by showing the adoption of an individual change from above to instigate a faithfully-transmitted counterclockwise chain shift in the regional French nasal vowel system.

scholarly journals Construction and solution of a Wannier-functions based Hamiltonian in the pseudopotential plane-wave framework for strongly correlated materials

2008 ◽  
Vol 65 (1) ◽  
pp. 91-98 ◽  
Author(s):  
Dm. Korotin ◽  
A. V. Kozhevnikov ◽  
S. L. Skornyakov ◽  
I. Leonov ◽  
N. Binggeli ◽  
...  
Keyword(s):  
Plane Wave ◽  
Strongly Correlated ◽  
Wannier Functions ◽  
Strongly Correlated Materials

scholarly journals Bad metallic transport in a cold atom Fermi-Hubbard system

Science ◽  
2018 ◽  
Vol 363 (6425) ◽  
pp. 379-382 ◽  
Author(s):  
Peter T. Brown ◽  
Debayan Mitra ◽  
Elmer Guardado-Sanchez ◽  
Reza Nourafkan ◽  
Alexis Reymbaut ◽  
...  
Keyword(s):  
Diffusion Constant ◽  
Cold Atom ◽  
Quantum Systems ◽  
Strong Interactions ◽  
Einstein Relation ◽  
Linear Temperature Dependence ◽  
Many Body ◽  
Linear Temperature ◽  
Density Modulation ◽  
Shed Light

Strong interactions in many-body quantum systems complicate the interpretation of charge transport in such materials. To shed light on this problem, we study transport in a clean quantum system: ultracold lithium-6 in a two-dimensional optical lattice, a testing ground for strong interaction physics in the Fermi-Hubbard model. We determine the diffusion constant by measuring the relaxation of an imposed density modulation and modeling its decay hydrodynamically. The diffusion constant is converted to a resistivity by using the Nernst-Einstein relation. That resistivity exhibits a linear temperature dependence and shows no evidence of saturation, two characteristic signatures of a bad metal. The techniques we developed in this study may be applied to measurements of other transport quantities, including the optical conductivity and thermopower.

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