Self-consistent<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>T</mml:mi></mml:math>-matrix theory of superconductivity

Šopík, Břetislav; Lipavský, Pavel; Männel, M.; Morawetz, Klaus; Matlock, Peter

doi:10.1103/physrevb.84.094529

Cited by 13 publications

(16 citation statements)

References 68 publications

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“…(21) By defining the Cooper-channel operator F (τ ) = q ψ ↑ (p 1 − q, τ )ψ ↓ (k + q, τ ), we have the relation (after analytical continuation) ImΠ(Q, W) = −ImW −2 [F (W) − F (0)] in center-ofmass framework, where F (W) = β 0 dτ e iωτ T F (τ )F † (0) . Note that the Green's functions in second line of the above equation are bare propagators (undressed/unrenormalized by the selfenergies), and thus it is possible to observe the instability (satisfy the Thouless criterion at zero-center-of-mass momentum and at critical temperature), as well as the gap equation [23]. Through this pair propagtor, the pole of above non-self-consistent T -matrix, at zero center-ofmass momentum Q = p 1 + k = 0, W = ω + Ω = 0, gives rise to a divergence which leads to the instability and gap.…”

Section: Correlations and Self-energies In Strong-coupling And Weak-c...mentioning

confidence: 99%

“…()), i.e., the Ward-identity T = ∂Σ/∂(iω) is broken, and the nonfluctuating order parameter φ(0) cannot affects this self-energy, i.e., the change of self-energy in phase space has δΣ(p, ω) = δ(H −H 0 )/δG(p, ω) = 0 (here H −H 0 ∼ g b /N; N is teh flavor number), thus the gap equation within above formula can simply be replaced by the fluctuating order parameter φ(q). Using the Ward identity [26], which is valid in both the self-consistent and non-self-consistent approximation [23], the order parameter here can also be replaced by the variation of the self energy δΣ(p, ω) = q,Ω T (q, Ω)δG(p − q, ω − Ω). Thus the poles of T -matrix also leads to the divergence of self-energy.…”

Section: Correlations and Self-energies In Strong-coupling And Weak-c...mentioning

confidence: 99%

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Bipolaron formed through electron-hole excitation

2020

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We investigate the electronic properties and electron correlations of the bipolaron formed by the electron-hole excitations in the presence of Yukawa-type coupling (between nonrelativistic fermions) in three spatial dimension. The electron-hole excitation, which is necessary to the formation of bipolaron, leads to imaginary particle-hole order parameter, and provide finite boson field mass to the single-polaron dispersion in a broken-symmetry phase. We found that the bipolaron exhibits fermi-liquid features as long as the long-range strong interaction is suppressed, and it behave differently compared to the single-polaron. The bosonic momentum determines the mass of boson field propagator and the gap function, and it also related to the self-energies and the single-particle Green's functions. The Thouless criterion is also used during the calculation of gap equation at critical temperature (which become lower in weakcoupling regime), which corresponds to the pole (instability) of the pair propagator in zero center-of-mass freamwork. The mean field term and the bosonic fluctuationinduced contribution to free energy in Aslamazov-Larkin-type bipolaron diagram are also studied.

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Section: Correlations and Self-energies In Strong-coupling And Weak-c...mentioning

confidence: 99%

Section: Correlations and Self-energies In Strong-coupling And Weak-c...mentioning

confidence: 99%

Bipolaron formed through electron-hole excitation

2020

Preprint

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“…Nevertheless, they lead to correct equations. Recently it has been shown that one can arrive at the same equations by a completely conserving theory of multiple corrected T‐matrix [ 56–58 ] with equivalent results. [ 59,60 ] This illustrates that the anomalous propagators are a theoretical shortcut to the right result through adopting inconsistent propagators.…”

Section: Introductionmentioning

confidence: 99%

Exploring Anomalies by Many‐Body Correlations

Morawetz

2021

Physica Status Solidi (b)

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The quantum anomaly is written alternatively into a form violating conservation laws or as non‐gauge invariant currents seen explicitly on the example of chiral anomaly. By reinterpreting the many‐body averaging, the connection to Pauli–Villars regularization is established which gives the anomalous term a new interpretation as arising from quantum fluctuations by many‐body correlations at short distances. This is exemplified using an effective many‐body quantum potential which realizes quantum Slater sums by classical calculations. It is shown that these quantum potentials avoid the quantum anomaly but approach the same anomalous result by many‐body correlations. Consequently, quantum anomalies might be a shortcut way of single‐particle field theory to account for many‐body effects. This conjecture is also supported since the chiral anomaly can be derived by a completely conserving quantum kinetic theory. A measure for the quality of quantum potentials is suggested to describe these quantum fluctuations in the mean energy. The derived quantum potentials might be used to describe quantum simulations in classical terms.

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“…The T -matrix theory which offers symmetric positions of peaks has been derived from the multiple-scattering approach [37,38]. The multiple-scattering theory is not based on the straightforward power expansion, therefore it cannot be represented by diagrams as long as one follows Feynman's rules to convert diagrams into formulas.…”

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confidence: 99%

“…If we correct only repeated collisions with the Cooper pairs involved, the modification of the theory in [38] can be expressed as the renormalized BCS theory. We now discuss this approximation.…”

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confidence: 99%