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Register a new userDynamical order and superconductivity in a frustrated many-body system
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In triangular lattice structures, spatial anisotropy and frustration can lead to rich equilibrium phase diagrams with regions containing complex, highly entangled states of matter. In this work we study the driven two-rung triangular Hubbard model and evolve these states out of equilibrium, observing how the interplay between the driving and the initial state unexpectedly shuts down the particle-hole excitation pathway. This restriction, which symmetry arguments fail to predict, dictates the transient dynamics of the system, causing the available particle-hole degrees of freedom to manifest uniform long-range order. We discuss implications of our results for a recent experiment on photo-induced superconductivity in ${rm kappa - (BEDT-TTF)_{2}Cu[N(CN)_{2}]Br}$ molecules.
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Motivated by recent experiments on magnetically frustrated heavy fermion metals, we theoretically study the phase diagram of the Kondo lattice model with a nonmagnetic valence bond solid ground state on a ladder. A similar physical setting may be naturally occurring in YbAl$_3$C$_3$, CeAgBi$_2$, and TmB$_4$ compounds. In the insulating limit, the application of a magnetic field drives a quantum phase transition to an easy-plane antiferromagnet, which is described by a Bose-Einstein condensation of magnons. Using a combination of field theoretical techniques and density matrix renormalization group calculations we demonstrate that in one dimension this transition is stable in the presence of a metallic Fermi sea and its universality class in the local magnetic response is unaffected by the itinerant gapless fermions. Moreover, we find that fluctuations about the valence bond solid ground state can mediate an attractive interaction that drives unconventional superconducting correlations. We discuss the extensions of our findings to higher dimensions and argue that, depending on the filling of conduction electrons, the magnon Bose-Einstein condensation transition can remain stable in a metal also in dimensions two and three.
We study the pump-probe response of three insulating cuprates and develop a model for its recombination kinetics. The dependence on time, fluence, and both pump and probe photon energies imply many-body recombination on femtosecond timescales, characterized by anomalously large trapping and Auger coefficients. The fluence dependence follows a universal form that includes a characteristic volume scale, which we associate with the holon-doublon excitation efficiency. This volume varies strongly with pump photon energy and peaks near twice the charge-transfer energy, suggesting that the variation is caused by carrier multiplication through impact ionization.
Non-Hermtian (NH) Hamiltonians effectively describing the physics of dissipative systems have become an important tool with applications ranging from classical meta-materials to quantum many-body systems. Exceptional points, the NH counterpart of spectral degeneracies, are among the paramount phenomena unique to the NH realm. While realizations of second-order exceptional points have been reported in a variety of microscopic models, higher-order ones have largely remained elusive in the many-body context, as they in general require fine tuning in high-dimensional parameter spaces. Here, we propose a microscopic model of correlated fermions in three spatial dimensions and demonstrate the occurrence of interaction-induced fourth-order exceptional points that are protected by chiral symmetry. We demonstrate their stability against symmetry breaking perturbations and investigate their characteristic analytical and topological properties.
Superconductivity and magnetic order strongly compete in many conventional superconductors, at least partly because both tend to gap the Fermi surface. In magnetically-ordered conventional superconductors, the competition between these cooperative phenomena leads to anomalies at magnetic and superconducting phase boundaries. Here we reveal that in Pr2Pt3Ge5 superconducting and multiple magnetic order are intertwined within the same HT-phase space, but remain completely decoupled. Our thermal conductivity measurements provide evidence for normal electrons in the superconducting phase from which magnetic order emerges with negligible coupling to electron bands that contribute to superconductivity.
A hypothetical layered oxide La_2NiMO_6 where NiO_2 and MO_2 planes alternate along the c-axis of ABO_3 perovskite lattice is considered theoretically. Here, M denotes a trivalent cation Al, Ga,... such that MO_2 planes are insulating and suppress the c-axis charge transfer. We predict that correlated e_g electrons in the NiO_2 planes develop a planar x^2-y^2 orbital order driven by the reduced dimensionality and further supported by epitaxial strain from the substrate. Low energy electronic states can be mapped to a single-band t-t-J model, suggesting favorable conditions for high-T_c superconductivity.
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