Pump Frequency Resonances for Light-Induced Incipient Superconductivity in YBa2Cu3O6.5
Physical Review X American Physical Society (APS) 10:1 (2020) 011053
Light-induced anomalous Hall effect in graphene.
Nature physics 16:1 (2020) 38-41
Abstract:
Many non-equilibrium phenomena have been discovered or predicted in optically-driven quantum solids1. Examples include light-induced superconductivity2,3 and Floquet-engineered topological phases4-8. These are short lived effects that should lead to measurable changes in electrical transport, which can be characterized using an ultrafast device architecture based on photoconductive switches9. Here, we report the observation of a light-induced anomalous Hall effect in monolayer graphene driven by a femtosecond pulse of circularly polarized light. The dependence of the effect on a gate potential used to tune the Fermi level reveals multiple features that reflect a Floquet-engineered topological band structure4,5, similar to the band structure originally proposed by Haldane10. This includes an approximately 60 meV wide conductance plateau centered at the Dirac point, where a gap of equal magnitude is predicted to open. We find that when the Fermi level lies within this plateau, the estimated anomalous Hall conductance saturates around 1.8±0.4 e2/h.Microscopic theory for the light-induced anomalous Hall effect in graphene
Physical Review B American Physical Society (APS) 99:21 (2019) 214302
Metastable ferroelectricity in optically strained SrTiO3.
Science (New York, N.Y.) 364:6445 (2019) 1075-1079
Abstract:
Fluctuating orders in solids are generally considered high-temperature precursors of broken symmetry phases. However, in some cases, these fluctuations persist to zero temperature and prevent the emergence of long-range order. Strontium titanate (SrTiO3) is a quantum paraelectric in which dipolar fluctuations grow upon cooling, although a long-range ferroelectric order never sets in. Here, we show that optical excitation of lattice vibrations can induce polar order. This metastable polar phase, observed up to temperatures exceeding 290 kelvin, persists for hours after the optical pump is interrupted. Furthermore, hardening of a low-frequency vibration points to a photoinduced ferroelectric phase transition, with a spatial domain distribution suggestive of a photoflexoelectric coupling.Measuring non-equilibrium dynamics in complex solids with ultrashort X-ray pulses.
Philosophical transactions. Series A, Mathematical, physical, and engineering sciences 377:2145 (2019) 20170478