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A methodology based on time-resolved, phase-sensitive second harmonic generation (SHG) for probing the excited state dynamics of species at interfaces is presented. It is based on an interference measurement between the SHG from the sample and a local oscillator generated at a reference together with a lock-in measurement to remove the large constant offset from the interference. The technique is characterized by measuring the phase and excited state dynamics of the dye malachite green at the water/air interface. The key attributes of the technique are that the observed signal is directly proportional to sample concentration, in contrast to the quadratic dependence from non-phase sensitive SHG, and that the real and imaginary parts of the 2nd order non-linear susceptibility can be determined independently. We show that the method is highly sensitive and can provide high quality excited state dynamics in short data acquisition times.
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http://dx.doi.org/10.1063/1.4909522 | DOI Listing |
Phys Rev Lett
August 2025
RIKEN Center for Quantum Computing, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
We present a method for probing the quantum capacitance associated with the Rydberg transition of surface electrons on liquid helium using radio-frequency (rf) reflectometry. Resonant microwave excitation of the Rydberg transition induces a redistribution of image charges on capacitively coupled electrodes, giving rise to a quantum capacitance originating from adiabatic state transitions and the finite curvature of the energy bands. By applying frequency-modulated resonant microwaves to drive the Rydberg transition, we systematically measured a capacitance sensitivity of 0.
View Article and Find Full Text PDFPhys Rev Lett
August 2025
University of Southern Denmark, Centre for Nano Optics, Campusvej 55, Odense M DK-5230, Denmark.
Controlling the spontaneous emission of nanoscale quantum emitters (QEs) is crucial for developing advanced photon sources required in many areas of modern nanophotonics, including quantum information technologies. Conventional approaches to shaping photon emission are based on using bulky configurations, while approaches recently developed in quantum metaphotonics suffer from limited capabilities in achieving desired polarization states and directionality, failing to provide on-demand photon sources tailored precisely to technological needs. Here, we propose a universal approach to designing versatile photon sources using on-chip QE-coupled meta-optics that enable direct transformations of QE-excited surface plasmon polaritons into spatially propagating photon streams with arbitrary polarization states, directionality, and amplitudes via both resonance and geometric phases supplied by scattering meta-atoms.
View Article and Find Full Text PDFPhys Rev Lett
August 2025
McMaster University, Department of Physics and Astronomy, Hamilton, Ontario L8S 4M1, Canada.
Magnetic heat capacity measurements of a high-quality single crystal of the dipole-octupole pyrochlore Ce_{2}Hf_{2}O_{7} down to a temperature of T=0.02 K are reported. These show a two-peaked structure, with a Schottky-like peak at T_{1}∼0.
View Article and Find Full Text PDFPhys Rev Lett
August 2025
Los Alamos National Laboratory, Theoretical Division, Los Alamos, New Mexico 87545, USA.
At the extreme densities in neutron stars, a phase transition to deconfined quark matter is anticipated. Yet masses, radii, and tidal deformabilities offer only indirect measures of a first-order phase transition, requiring many detections to resolve or being ineffective observables if the discontinuity exists at lower densities. We report on a smoking-gun gravitational-wave signature of a first-order transition: the resonant tidal excitation of an interface mode.
View Article and Find Full Text PDFPhys Rev Lett
August 2025
Xiamen University, College of Physical Science and Technology, School of Electronic Science and Engineering, State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, College of Energy, Fujian Key Laboratory of Ultrafast Laser Technology and Applica
The photonic flat band, defined by minimal dispersion and near-zero group velocity, has facilitated significant advances in optical technologies. The practical applications of flat bands, such as enhanced light-matter interactions, require efficient coupling to far-field radiation. However, achieving controlled coupling between flat bands and their corresponding localized modes with far-field radiation remains challenging and elusive.
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