Continuum of many-particle states near the metal-insulator transition in the Hubbard model

Sherman, A.

doi:10.1140/epjb/e2017-80082-y

Cited by 6 publications

(19 citation statements)

References 42 publications

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“…It is worth noting that the dashed curve in this figure nearly coincides with the metal-insulator boundary found in Ref. [20], in which only diagrams (a), (b) and (e) in Fig. 1 were taken into account, that is only short-range spin and charge fluctuations were considered.…”

Section: Comparison With Results Of Other Methods and Sum Rulessupporting

confidence: 76%

Influence of spin and charge fluctuations on spectra of the two-dimensional Hubbard model

Sherman

2018

J. Phys.: Condens. Matter

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The influence of spin and charge fluctuations on spectra of the two-dimensional fermionic Hubbard model is considered using the strong coupling diagram technique. Infinite sequences of diagrams containing ladder inserts, which describe the interaction of electrons with these fluctuations, are summed, and obtained equations are self-consistently solved for the ranges of Hubbard repulsions [Formula: see text], temperatures [Formula: see text] and electron concentrations [Formula: see text] with t the intersite hopping constant. For all considered U the system exhibits a transition to the long-range antiferromagnetic order at [Formula: see text]. At the same time no indication of charge ordering is observed. Obtained solutions agree satisfactorily with results of other approaches and obey moments sum rules. In the considered region of the U-T plane, the curve separating metallic solutions passes from [Formula: see text] at the highest temperatures to U = 2t at [Formula: see text] for half-filling. If only short-range fluctuations are allowed for the remaining part of this region is occupied by insulating solutions. Taking into account long-range fluctuations leads to strengthening of maxima tails, which transform a part of insulating solutions into bad-metal states. For low T, obtained results allow us to trace the gradual transition from the regime of strong correlations with the pronounced four-band structure and well-defined Mott gap for [Formula: see text] to the Slater regime of weak correlations with the spectral intensity having a dip along the boundary of the magnetic Brillouin zone due to an antiferromagnetic ordering for [Formula: see text]. For [Formula: see text] and [Formula: see text] doping leads to the occurrence of a pseudogap near the Fermi level, which is a consequence of the splitting out of a narrow band from a Hubbard subband. Obtained spectra feature waterfalls and Fermi arcs, which are similar to those observed in hole-doped cuprates.

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Section: Comparison With Results Of Other Methods and Sum Rulessupporting

confidence: 76%

Influence of spin and charge fluctuations on spectra of the two-dimensional Hubbard model

Sherman

2018

J. Phys.: Condens. Matter

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“…A similar flattening of the spin-polaron band and a persistent DOS peak at the FL were observed in the t-J model [38,39]. In two dimensions (2D), the momentum dependence of the electron self-energy is rather strong [16,23,40], and the applicability of the DMFA ideas, in this case, is not evident. We argue that the peak at the FL (for brevity, the FL peak) may explain some peculiarities of photoemission spectra in the n-type crystal Nd 2−x Ce x CuO 4 [41,42,43,44].…”

Section: Introductionsupporting

confidence: 65%

“…Up to the constant factor χ(l ′ , τ ′ ; l, τ ) (3) coincides with the spin susceptibility. For calculating these quantities the SCDT [10,11,12,13] is used (a concise description of this diagram technique can be found in [40]). In this approach, the Fourier transform of Green's function (2) can be presented in the form…”

Section: Main Formulasmentioning

confidence: 99%

The t−t′−t″−U Hubbard model and Fermi-level peak

Sherman¹

2019

Phys. Scr.

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Using the strong coupling diagram technique, low-temperature spectral properties of the two-dimensional fermionic Hubbard model are considered for strong and moderate Hubbard repulsions U . The electron hopping to the nearest, second and third neighbors is taken into account with hopping constants t, t ′ = −0.3t and t ′′ = 0.2t, respectively. The nonzero values of t ′ and t ′′ lead to strong asymmetry in magnetic properties with respect to the hole and electron doping -for U = 8t strong antiferromagnetic correlations are retained up to the electron concentrationn ≈ 1.25, while they are destroyed completely atn ≈ 0.87. When the temperature is decreased to T 0.1t, in a wide range of electron concentrations there appear narrow and intensive peaks at the Fermi level in densities of states. For U 6t the peaks are seen even at half-filling, while for larger U they arise as the Fermi level leaves the Mott gap. The peaks are connected with a narrow band emerging at low temperatures. We identify states forming the band with spin-polaron excitations -bound states of correlated electrons and mobile spin excitations. Obtained low-temperature spectral functions are used for interpreting the peak-dip-hump structure observed in the photoemission of Nd 2−x CexCuO 4 . In the case of hole doping, the calculated Fermi contour contains arcs near nodal points with pseudogaps near antinodal points, while for electron doping the spectral intensity is suppressed at hot spots, in agreement with experimental observations in cuprate perovskites.

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“…3 For other considered values of U transitions temperatures were found also to be close to those obtained in Ref. [3]. It can be concluded that short-range fluctuations play the main role in determining the locations of the transition curve in the considered parameter ranges.…”

Section: Results Of Calculationssupporting

confidence: 84%

Manifestations of spin and charge fluctuations in spectra of the Hubbard model

Sherman

2018

Int. J. Mod. Phys. B

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The influence of long-range spin and charge fluctuations on spectra of the twodimensional fermionic Hubbard model is considered using the strong coupling diagram technique. Infinite sequences of diagrams containing ladder inserts, which describe the interaction of electrons with these fluctuations, are summed, and obtained equations are self-consistently solved for the range of Hubbard repulsions 4t ≤ U ≤ 8t and temperatures 0.3t T t with t the intersite hopping constant. It was found that a metalinsulator transition curve goes from larger U and T to smaller values of these parameters. The temperature decrease causes the transition to the long-range antiferromagnetic order. It is responsible for the splitting out of a narrow band from a Hubbard subband with doping for U = 8t and low T . This segregated band is located near the Fermi level and forms a pseudogap here.

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Continuum of many-particle states near the metal-insulator transition in the Hubbard model

Cited by 6 publications

References 42 publications

Influence of spin and charge fluctuations on spectra of the two-dimensional Hubbard model

Influence of spin and charge fluctuations on spectra of the two-dimensional Hubbard model

The t−t′−t″−U Hubbard model and Fermi-level peak

Manifestations of spin and charge fluctuations in spectra of the Hubbard model

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