arXiv subjects

Jannis Seufert

Publications and source records attributed to Jannis Seufert.

8 recordsLinked to original sources

arXiv2026

Slave-boson Formalism for Superconducting Pairing at Strong Coupling

We study the emergence of superconductivity in the one-band Hubbard model using the spin-rotation-invariant Kotliar-Ruckenstein slave-boson (SB) approach. Motivated by its intrinsically renormalized mean-field ground state, we construct an effective pairing vertex from dynamical fluctuations about the saddle point. Solving the anisotropic, frequency-dependent gap equation on the square lattice, we map the pairing instabilities across doping, interaction, temperature and real-frequency gap structure that qualitatively match experimental cuprate observations. This framework merges strong-correlation SB-type renormalizations with RPA-type pairing transparency, providing a scalable route to modeling multi-orbital superconductivity at strong coupling.

cond-mat.supr-con↗

arXiv2026

Altermagnons at the metal-insulator transition

By means of slave-boson theory for the Hubbard model on the checkerboard lattice, we calculate dynamical altermagnetic spin susceptibilities from the metallic to the Mott-insulating regime. We track magnon dispersion and lifetime renormalization, allowing us to uncover a crossover from a chirality-selective dissipation of magnon modes to coherent yet strongly deformed chiral magnon branches across the metal insulator transition. Our formalism lends itself to a quantitative description of collective spin dynamics in correlated altermagnets.

cond-mat.str-el↗

arXiv2026

Altermagnetic phase transition in a Lieb metal

We analyze the phase transition between a symmetric metallic parent state and itinerant altermagnetic order. The underlying mechanism we reveal in our microscopic model of electrons on a Lieb lattice does not involve orbital ordering, but derives from sublattice interference.

cond-mat.str-el↗

arXiv2026

Engineering altermagnetic orders on the square-kagome lattice through sublattice interference

We investigate the emergence of altermagnetic (AM) phases on the square-kagome lattice. Our analysis reveals that matrix element effects due to an orthogonal sublattice weight decomposition of Fermi level eigenstates known as sublattice interference enable decoupled magnetic ordering tendencies on distinct sublattices. Depending on which sublattice undergoes a magnetic instability, we identify a $d_{xy}$-type AM phase and a $d_{x^{2}-y^{2}}$-type AM phase originating from different sublattice polarization patterns. Using the Kotliar-Ruckenstein slave boson formalism we explore the stability of these AM phases as a function of interaction strength. Our findings demonstrate that sublattice-selective magnetic instabilities provide a versatile route to engineer the nature of AM order.

cond-mat.str-el↗

arXiv2025

Fluctuation corrections to the free energy of strongly correlated electron systems

We determine the free energy of strongly correlated electron systems in the example of the Hubbard model by calculating the contribution of spin and charge fluctuations to the Gutzwiller approximation mean field result. We employ the slave boson formulation of Kotliar and Ruckenstein in its spin-rotation invariant form in the usual continuous time approximation of the functional integral representation, corrected by "high frequency contributions" (SRIKR+). Previous method-related shortcomings are shown to be overcome when the correct operator ordering for the renormalized kinetic energy is used. The results for the ground state energy in the paramagnetic phase are in very good agreement with state-of-the-art results obtained by methods such as density matrix embedded theory (DMET), quantum Monte Carlo (QMC) and others. The leading low temperature behavior of the free energy allows to extract the quasiparticle effective mass, in particular its enhancement near a continuous phase transition into an ordered state. Our work demonstrates that the SRIKR+ method is competitive with the best available alternative methods and equips the slave-boson approach with an improved synoptic power to explore strongly correlated electron systems.

cond-mat.str-el↗

arXiv2024

Incommensurate magnetic order: A fingerprint for electronic correlations in hole-doped cuprates

Intertwined charge and magnetic fluctuations in high-$T_\text{c}$ copper oxide superconductors (cuprates) are hypothesized to be a consequence of their correlated electronic nature. Among other observables, this is apparent in the doping dependence of incommensurate magnetic order, known as the Yamada relation (YR). We analyze the Hubbard model to challenge the universality of YR as a function of interaction strength $U$ through Kotliar-Ruckenstein slave-boson (SB) mean-field theory and truncated unity functional renormalization group (TUFRG). While TUFRG tends to lock in to a doping dependence of the incommensurate magnetic ordering vector obtained for the perturbative weak-coupling limit, SB not only exhibits an enhanced sensitivity upon a variation of $U$ from weak to strong coupling, but also shows good agreement with experimental data. It supports the placement of weakly hole-doped cuprates in the intermediate-to-strong coupling regime.

cond-mat.str-el↗

arXiv2023

Maple Leaf Antiferromagnet in a Magnetic Field

We analyze the quantum antiferromagnet on the maple leaf lattice in the presence of a magnetic field. Starting from its exact dimer ground state and for a magnetic field strength of the order of the local dimer spin exchange coupling, we perform a strong coupling expansion and extract an effective hardcore boson model. The interplay of effective many-body interactions, suppressed single-particle dynamics, and correlated hopping gives way to an intriguing series of superfluid to insulator transitions which correspond to magnetization plateaux in terms of the maple leaf spin degrees of freedom. While we find plateaux at intermediate magnetization to be dominated by bosonic density wave order, we conjecture plateau formation from multi-boson bound states due to correlated hopping for lower magnetization.

cond-mat.str-el↗

arXiv2023

Interplay of spin and charge order in the electron-doped cuprates

We study magnetic and charge order in the electron-doped high-$T_c$ cuprates based on the one-band Hubbard model with onsite ($U$) and nearest-neighbor $(V)$ interactions. To investigate the interplay between the orders, we employ the Kotliar-Ruckenstein slave-boson method and analyze fluctuations descending from an antiferromagnetic parent state. Our analysis reveals incommensurate charge order whose ordering vector matches the doping-dependence of resonant inelastic x-ray scattering (RIXS) measurements in Nd$_{2-x}$Ce$_x$CuO$_4$ (NCCO). From our calculations of paramagnon dispersion as well as dynamical charge and spin structure factors, we reproduce all qualitative features of the RIXS signal.

cond-mat.str-el↗