Role of nonspherical double counting in DFT+DMFT: Total energy and structural optimization of pnictide superconductors

Kristanovski, Oleg; Shick, A. B.; Lechermann, Frank; Lichtenstein, A. I.

doi:10.1103/physrevb.97.201116

Cited by 14 publications

(7 citation statements)

References 40 publications

(44 reference statements)

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“…An additional non-spherical double-counting correction is used, described in Refs. [11,12]. Following a conventional approach, we make use of reduced atomic Hartree-Fock values [13] of the Slater integrals F 2 = 6.20 eV, F 4 = 4.03 eV, and F 6 = 2.94 eV.…”

Section: Methodsmentioning

confidence: 99%

Spin-Orbit Coupling Induced Degeneracy in the Anisotropic Unconventional Superconductor UTe$_2$

Shick,

Pickett

2019

Preprint

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The orthorhombic uranium dichalcogenide UTe2 displays superconductivity below 1.7 K, with the anomalous feature of retaining 50% of normal state (ungapped) carriers, according to heat capacity data from two groups. Incoherent transport that crosses over from above 50 K toward a low temperature, Kondo lattice Fermi liquid regime indicates strong magnetic fluctuations and the need to include correlation effects in theoretical modeling. We report density functional theory plus Hubbard U (DFT+U) results for UTe2 to provide a platform for modeling its unusual behavior, focusing on ferromagnetic (FM, time reversal breaking) long range correlations along the â axis as established by magnetization measurements and confirmed by our calculations. States near the Fermi level are dominated by the j = 5 2 configuration, with the jz = ± 1 2 sectors being effectively degenerate and half-filled. Unlike the small-gap insulating nonmagnetic electronic spectrum, the FM Fermi surfaces are large (strongly metallic) and display low dimensional features, reminiscent of the FM superconductor UGe2.

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Section: Methodsmentioning

confidence: 99%

Spin-Orbit Coupling Induced Degeneracy in the Anisotropic Unconventional Superconductor UTe$_2$

Shick,

Pickett

2019

Preprint

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“…calculated in a single-site approximation as described previously, [24,26] from which 5f orbital occupations are obtained. V BZ is the volume of the Brillouin zone (BZ).…”

Section: Local Approximation For σ(Z)mentioning

confidence: 99%

“…( 7) acting on the f -states is corrected to exclude the non-spherical double-counting with V U . [26] The equations in Eq. ( 7) are iteratively solved until selfconsistency over the charge density is reached.…”

Section: Density Matrix Self-consistencymentioning

confidence: 99%

UTe$_2$: a nearly insulating half-filled $j=\frac{5}{2}$ $5f^3$ heavy fermion metal

Shick,

Fujimori,

Pickett

2021

Preprint

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Correlated band theory implemented as a combination of density functional theory with exact diagonalization [DFT+U(ED)] of the Anderson impurity term with Coulomb repulsion U in the open 14-orbital 5f shell is applied to UTe2. The small gap for U =0, evidence of the half-filled j = 5 2 subshell of 5f 3 uranium, is converted for U =3 eV to a flat band semimetal with small heavy-carrier Fermi surfaces that will make properties sensitive to pressure, magnetic field, and offstoichiometry, as observed experimentally. Two means of identification from the Green's function give a mass enhancement of the order of 12 for already heavy (flat) bands, consistent with the common heavy fermion characterization of UTe2. The predicted Kondo temperature around 100 K matches the experimental values from resistivity. The electric field gradients for the two Te sites are calculated by DFT+U(ED) to differ by a factor of seven, indicating a strong site distinction, while the anisotropy factor η = 0.18 is similar for all three sites. The calculated uranium moment < M 2 > 1/2 of 3.5µB is roughly consistent with the published experimental Curie-Weiss values of 2.8µB and 3.3µB (which are field-direction dependent), and the calculated separate spin and orbital moments are remarkably similar to Hund's rule values for an f 3 ion. The U =3 eV spectral density is compared with angle-integrated and angle-resolved photoemission spectra, with agreement that there is strong 5f character at, and for several hundred meV below, the Fermi energy. Our results support the picture that the underlying ground state of UTe2 is that of a half-filled j = 5 2 subshell with two half-filled mj = ± 1 2 orbitals forming a narrow gap by hybridization, then driven to a conducting state by configuration mixing (spin-charge fluctuations). UTe2 displays similarities to UPt3 with its 5f dominated Fermi surfaces rather than a strongly localized Kondo lattice system.

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“…A recent development on the DC problem is the derivation of an exact DC expression using a continuum representation of DMFT (46). This approach takes into account the nonsphericity of the impurity, and has so far produced good agreement with the experiment (36,47), possibly concluding the discussion over the different DC approaches. Another area where there is need for new developments is the numerical impurity solvers, which solve the AIM to calculate the self energy Σ(ω) from the hybridization ∆(ω) (8).…”

Section: First Principles Dft+dmftmentioning

confidence: 99%

Section: First Principles Dft+dmftmentioning

confidence: 99%

Applications of DFT + DMFT in Materials Science

Paul

Birol

2019

Annu. Rev. Mater. Res.

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First principles methods can provide insight into materials that otherwise is impossible to acquire. Density Functional Theory (DFT) has been the first principles method of choice for numerous applications, but it falls short of predicting the properties of correlated materials. First principles Density Functional Theory + Dynamical Mean Field Theory (DFT+DMFT) is a powerful tool that can address these shortcomings of DFT when applied to correlated metals. In this brief review, which is aimed at non-experts, we review the basics and some applications of DFT+DMFT.

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Role of nonspherical double counting in DFT+DMFT: Total energy and structural optimization of pnictide superconductors

Cited by 14 publications

References 40 publications

Spin-Orbit Coupling Induced Degeneracy in the Anisotropic Unconventional Superconductor UTe$_2$

Spin-Orbit Coupling Induced Degeneracy in the Anisotropic Unconventional Superconductor UTe$_2$

UTe$_2$: a nearly insulating half-filled $j=\frac{5}{2}$ $5f^3$ heavy fermion metal

Applications of DFT + DMFT in Materials Science

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