arXiv subjects

I. A. Goremykin

Publications and source records attributed to I. A. Goremykin.

4 recordsLinked to original sources

arXiv2026

The pseudogap in high-$T_c$ superconductors from SU(2) gauge symmetry and dynamic correlation effects

We consider the spectral properties of the two-dimensional Hubbard model, describing the electronic properties of high-$T_c$ compounds, within the SU(2) gauge theory, which assumes the separation of electronic degrees of freedom into those of spinon and chargon subsystems. We use the dynamic mean-field theory (DMFT) approach to describe magnetic long-range order in the chargon subsystem while also treating spinon fluctuations on top of this state. We show that DMFT supplemented by long-wavelength magnetic fluctuations is essential for describing the asymmetry in the damping between the inner and outer regions of the hole pockets and the resulting formation of Fermi arcs in the underdoped regime, especially at low hole doping. The underlying hole pockets in the chargon subsystem can be associated with those observed in quantum oscillation measurements.

cond-mat.str-el↗

arXiv2025

Frequency dependence of temporal spin stiffness and short-range magnetic order in the doped two-dimensional Hubbard model

We study doping and temperature dependencies of temporal and spatial spin stiffnesses of the Hubbard model within the mean field approach for incommensurate magnetic order. We show that the frequency dependence of temporal spin stiffness within the considered mean-field approach is crucial to obtain small values of correlation length, comparable to those observed in cuprates. Using the obtained spin stiffnesses, we obtain the temperature and doping dependence of correlation length within the large-$N$ limit of the respective nonlinear sigma model. In agreement with the experimental data on La$_{2-x}$Sr$_x$CuO$_4$ we obtain short range magnetic order with relatively small correlation length at $0.1 \lesssim x\lesssim 0.2$, and magnetically ordered ground state in the narrow doping region $0.05\lesssim x \lesssim 0.1$. The latter state may correspond to the spin-frosen state, observed in the experimental data on La$_{2-x}$Sr$_x$CuO$_4$.

cond-mat.str-el↗

arXiv2024

Antiferromagnetic and spin spiral correlations in the doped two-dimensional Hubbard model: gauge symmetry, Ward identities, and dynamical mean-field theory analysis

We reconsider the derivation of Ward identities for spin stiffnesses, which determine the non-linear sigma model of magnetic degrees of freedom of interacting electrons in the presence of antiferromagnetic or incommensurate correlations. We emphasize that in the approaches, which do not break explicitly spin symmetry of the action, the spatial components of gauge kernel, which is used to obtain spin stiffnesses, remain gauge invariant even in case of spontaneous spin symmetry breaking. We derive the corrected Ward identities, which account for this gauge invariance. We emphasize that the frequency dependence of temporal spin stiffnesses is not fixed by the obtained identities, and show that the infinitesimally small external staggered field is crucially important to obtain finite static uniform transverse susceptibility. On the other hand, we find that the spatial spin stiffnesses are determined by the gauge kernel of the Legendre transformed theory, which is in general {\it different} from the gauge kernel of the original theory and obtain an explicit expressions for spatial spin stiffnesses through susceptibilities and current correlation functions. We verify numerically the obtained results within dynamic mean field theory, and obtain doping dependencies of the resulting spin stiffnesses for antiferromagnetic and incommensurate phase.

cond-mat.str-el↗

arXiv2023

Commensurate and incommensurate magnetic order in the doped two-dimensional Hubbard model: dynamical mean-field theory analysis

We develop a dynamical mean-field theory approach for the spiral magnetic order, changing to a local coordinate frame with preferable spin alignment along the $z$-axis, which can be considered with the impurity solvers treating the spin diagonal local Green's function. We furthermore solve the Bethe-Salpeter equations for nonuniform dynamic magnetic susceptibilities in the local coordinate frame. We apply this approach to describe the evolution of magnetic order with doping in the $t-t'$ Hubbard model with $t'=0.15$, which is appropriate for the description of the doped La$_2$CuO$_4$ high-temperature superconductor. We find that with doping the antiferromagnetic order changes to the $(Q,π)$ incommensurate one, and then to the paramagnetic phase. The spectral weight at the Fermi level is suppressed near half filling and continuously increases with doping. The dispersion of holes in the antiferromagnetic phase shows qualitative agreement with the results of the $t$-$J$ model consideration. In the incommensurate phase we find two branches of hole dispersions, one of which crosses the Fermi level. The resulting Fermi surface forms hole pockets. We also consider the dispersion of the magnetic excitations, obtained from the non-local dynamic magnetic susceptibilities. The transverse spin excitations are gapless, fulfilling the Goldstone theorem; in contrast to the mean-field approach the obtained magnetic state is found to be stable. The longitudinal excitations are characterized by a small gap, showing the rigidity of the spin excitations. For realistic hopping and interaction parameters we reproduce the experimentally measured spin-wave dispersion of La$_2$CuO$_4$.

cond-mat.str-el↗