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

Ulaga, Martin; Mravlje, Jernej; Kokalj, Jure

doi:10.1103/physrevb.103.155123

Cited by 9 publications

(11 citation statements)

References 38 publications

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“…Intriguingly, related measurements of spin diffusivity revealed a disagreement between the numerical methods and the experiment [2]. An independent numerical investigation confirmed the results of the theory [4] but disagrees with the experiment.…”

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confidence: 79%

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Spin Seebeck coefficient and spin-thermal diffusion in the two-dimensional Hubbard model

Mravlje,

Ulaga,

Kokalj

2021

Preprint

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We investigate the spin Seebeck coefficient Ss in the square lattice Hubbard model at high temperatures of relevance to cold-atom measurements. We solve the model with the finite-temperature Lanczos and with the dynamical mean-field theory methods and find they give similar results in the considered regime. Ss exceeds the atomic 'Heikes' estimates and the Kelvin entropic estimates drastically. We analyze the behavior in terms of a mapping onto the problem of a doped attractive model and derive an aproximate expression that allows relating the enhancement of Ss to distinct scattering of the spin-majority and spin-minority excitations. Our analysis reveals the limitations of entropic interpretations of Seebeck coefficient even in the high-temperature regime. Large values of Ss could be observed on optical lattices and might need to be taken into account to properly explain the measured values of spin diffusion.

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confidence: 79%

“…The values of specific heat are of the order of 0.3k B , hence the correction of the estimated spin-conductivity due to nonvanishing S s for magnetization 0.05 which is reasonable would be at the 20% level, which is not negligible but seems insufficient to explain the discrepancy with the experiment [2,4].…”

mentioning

confidence: 85%

Spin Seebeck coefficient and spin-thermal diffusion in the two-dimensional Hubbard model

Mravlje,

Ulaga,

Kokalj

2021

Preprint

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“…This is due to strong decrease of D Q,el at such T (see Fig. 1c) and originates in the shift from particle dominating heat transport to the spin (wave) dominated heat transport at lower T and accompanying strong decrease of the average velocity v determining the diffusion constant D = vl/2 [12]. The velocity v decreases from the order of v ∼ ta to the order of v ∼ Ja.…”

Section: Mott Insulatormentioning

confidence: 89%

“…One can try to get more insight with phenomenological considerations. We take c el from FTLM Heisenberg model result and approximate the velocity with a spin wave velocity v ∼ 1.4Ja [12,49,50] and the mean free path by the spin-spin correlation length ξ from renormalization group calculations [49,51]…”

Section: Mott Insulatormentioning

confidence: 99%

“…Similarly one can reexpress the spin conductivity σ s = χ s D s (with χ s being a uniform spin susceptibility and D s being a spin diffusion constant), which was used in a study of spin transport in cold atoms [11]. Spin diffusion constant has a non-monotonic T -dependence and reaches values below the lower limit of charge diffusion, which arises from the velocity being reduced from a value given by hopping t to that given by a (lower) Heisenberg exchange J [11,12]. Thermal conductivity can also be discussed in terms of the corresponding Nernst-Einstein relation κ = cD Q (with c being the specific heat and D Q the heat diffusion constant).…”

Section: Introductionmentioning

confidence: 99%

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Thermal conductivity and heat diffusion in the two-dimensional Hubbard model

Ulaga¹,

Mravlje²,

Prelovšek³

et al. 2022

Preprint

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We study the electronic thermal conductivity κ el and the thermal diffusion constant D Q,el in the square lattice Hubbard model using the finite-temperature Lanczos method. We exploit the Nernst-Einstein relation for thermal transport and interpret the strong non-monotonous temperature dependence of κ el in terms of that of D Q,el and the electronic specific heat c el . We present also the results for the Heisenberg model on a square lattice and ladder geometries. We study the effects of doping and consider the doped case also with the dynamical mean-field theory. We show that κ el is below the corresponding Mott-Ioffe-Regel value in almost all calculated regimes, while the mean free path is typically above lattice spacing. We discuss the opposite effect of quasi-particle renormalization on the electronic heat and charge diffusion constants. The calculated Lorenz ratio differs from the Sommerfeld value. We present results for the anisotropic marginal Fermi liquid model and discuss the results in relation to experiments on cuprates.

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Spin transport of a doped Mott insulator in moiré heterostructures

Regan,

Lu,

Wang

et al. 2024

Nat Commun

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Moiré superlattices of semiconducting transition metal dichalcogenide heterobilayers are model systems for investigating strongly correlated electronic phenomena. Specifically, WSe2/WS2 moiré superlattices have emerged as a quantum simulator for the two-dimensional extended Hubbard model. Experimental studies of charge transport have revealed correlated Mott insulator and generalized Wigner crystal states, but spin transport of the moiré heterostructure has not yet been sufficiently explored. Here, we use spatially and temporally resolved circular dichroism spectroscopy to directly image the spin transport as a function of carrier doping and temperature in WSe2/WS2 moiré heterostructures. We observe diffusive spin transport at all hole concentrations at 11 Kelvin — including the Mott insulator at one hole per moiré unit cell — where charge transport is strongly suppressed. At elevated temperatures the spin diffusion constant remains unchanged in the Mott insulator state, but it increases significantly at finite doping away from the Mott state. The doping- and temperature-dependent spin transport can be qualitatively understood using a t–J model, where spins can move via the hopping of spin-carrying charges and via the exchange interaction.

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

Cited by 9 publications

References 38 publications

Spin Seebeck coefficient and spin-thermal diffusion in the two-dimensional Hubbard model

Spin Seebeck coefficient and spin-thermal diffusion in the two-dimensional Hubbard model

Thermal conductivity and heat diffusion in the two-dimensional Hubbard model

Spin transport of a doped Mott insulator in moiré heterostructures

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