Dynamical order and superconductivity in a frustrated many-body system
Physical Review Letters American Physical Society 125 (2020) 137001
Abstract:
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 photoinduced superconductivity in κ − ( BEDT − TTF ) 2 Cu [ N ( CN ) 2 ] Br molecules.Photo-molecular high temperature superconductivity
Physical Review X American Physical Society 10 (2020) 031028
Abstract:
The properties of organic conductors are often tuned by the application of chemical or external pressure, which change orbital overlaps and electronic bandwidths while leaving the molecular building blocks virtually unperturbed. Here, we show that, unlike any other method, light can be used to manipulate the local electronic properties at the molecular sites, giving rise to new emergent properties. Targeted molecular excitations in the charge-transfer salt κ−(BEDT−TTF)2 Cu[N(CN)2] Br induce a colossal increase in carrier mobility and the opening of a superconducting optical gap. Both features track the density of quasiparticles of the equilibrium metal and can be observed up to a characteristic coherence temperature T∗≃50K, far higher than the equilibrium transition temperature TC=12.5K. Notably, the large optical gap achieved by photoexcitation is not observed in the equilibrium superconductor, pointing to a light-induced state that is different from that obtained by cooling. First-principles calculations and model Hamiltonian dynamics predict a transient state with long-range pairing correlations, providing a possible physical scenario for photomolecular superconductivity.Photoinduced electron pairing in a driven cavity
Physical Review Letters American Physical Society 125:5 (2020) 053602
Abstract:
We demonstrate how virtual scattering of laser photons inside a cavity via two-photon processes can induce controllable long-range electron interactions in two-dimensional materials. We show that laser light that is red(blue)-detuned from the cavity yields attractive(repulsive) interactions, whose strength is proportional to the laser intensity. Furthermore, we find that the interactions are not screened effectively except at very low frequencies. For realistic cavity parameters, laserinduced heating of the electrons by inelastic photon scattering is suppressed and coherent electron interactions dominate. When the interactions are attractive, they cause an instability in the Cooper channel at a temperature proportional to the square root of the driving intensity. Our results provide a novel route for engineering electron interactions in a wide range of two-dimensional materials including AB-stacked bilayer graphene and the conducting interface between LaAlO3 and SrTiO3.Probing photoinduced rearrangements in the NdNiO3 magnetic spiral with polarization-sensitive ultrafast resonant soft x-ray scattering
Physical Review B American Physical Society (APS) 102:1 (2020) 014311
Polarizing an antiferromagnet by optical engineering of the crystal field
Nature Physics Nature Research 16 (2020) 937-941