Phys.org September 27, 2024 Excitons in monolayer semiconductors offer strong light–matter coupling, spin–valley locking and exceptional tunability allowing electrical switching of their optical response due to efficient interactions of excitonic emitters with free charge carriers forming trions and Fermi polarons. However, there are major limitations to how fast the light emission of these states can be tuned, restricting most applications to an essentially static regime. An international team of researchers (Italy, Sweden, Germany, Japan) demonstrated switching of excitonic light emitters in monolayer semiconductors on ultrafast picosecond time scales by applying short pulses in the terahertz spectral range following optical injection. […]
Category Archives: Light- matter interaction
Study proposes generalized approach to light-matter interactions
Phys.org August 26, 2024 An international team of researchers (USA – University of Chicago, Italy) described a solution for the eigenstate problem of mixed fermion-boson systems that could be implemented on quantum devices. Based on a generalization of the electronic contracted Schrödinger equation (CSE), they guided a trial wave function to the ground state of any arbitrary mixed Hamiltonian by directly measuring residuals of the mixed CSE on a quantum device. The accuracy of their approach was not limited by the unknown exchange-correlation functional or the uncontrolled form of the exponential assumption. To test the performance of the method, they […]
Quantum dance to the beat of a drum: Researchers observe how energy of single electron is tuned by surrounding atoms
Phys.org March 14, 2024 Direct observation of the relevant interplay of the electronic structure of a single defect with other microscopic elementary excitations on their intrinsic length, time and energy scales has not been achieved. Researchers in Germany directly resolved in space, time, and energy how a spin–orbit-split energy level of an isolated selenium vacancy in a moiré-distorted WSe2 monolayer evolved under the controlled excitation of lattice vibrations. By locally launching a phonon oscillation and taking ultrafast energy-resolved snapshots of the vacancy’s states faster than the vibration period, they directly measured the impact of electron–phonon coupling in an isolated single-atom […]
Scientists push the boundaries of manipulating light at the submicroscopic level
Phys.org March 2, 2023 How tightly the light is confined determines the limits for the observability of nanoparticles, as well as the intensity and the precision of light-based devices. An international team of researchers (UK, Germany) has developed a general theory describing multi-mode light–matter coupling in systems of reduced dimensionality. The researchers explored their phenomenology, validating their theory’s predictions against numerical electromagnetic simulations. They characterized the spectral features linked with the multi-mode nature of the polaritons and showed how the interference between different photonic resonances can modify the real-space shape of the electromagnetic field associated with each polariton mode. According […]
Nanoparticles make it easier to turn light into solvated electrons
Nanowerk January 17, 2023 Solvated electrons are powerful reducing agents capable of driving some of the most energetically expensive reduction reactions. It has been proposed that solvated electrons, which are powerful reducing agents, could be produced by photoexcitation of roughened metal electrodes, but no study has demonstrated a clear mechanism for their generation. A team of researchers in the US (Rice University, Stanford University, UT Austin) has shown that plasmons create solvated electrons in water. They showed that the yield of solvated electrons in water was increased more than 10 times for nanoparticle-decorated electrodes compared to smooth silver electrodes. Based […]
Electrons on the run: On chirality, tunneling and light fields
Phys.org December 23, 2022 Tunnel ionization is of paramount importance in strong-field physics and attoscience. However, the tunneling dynamics and properties of the outgoing electronic wave packets often remain hidden beneath the influence of the subsequent scattering of the released electron onto the ionic potential. An international team of researchers (France, Israel) has characterized the influence of sub-barrier dynamics on the amplitude and phase of the wave packets emerging from the tunnel using chiral molecules, whose photoionization by circularly polarized light produces forward-backward asymmetric electron distributions with respect to the light propagation direction. The asymmetric patterns provided a background-free signature […]
Researchers unlock light-matter interactions on sub-nanometer scales, leading to ‘picophotonics’
Phys.org November 16, 2022 The concept of photonic frequency-momentum (ω-q) dispersion has been extensively studied in artificial dielectric structures such as photonic crystals and metamaterials, but not in in natural materials at the atomistic level. Researchers at Purdue University have developed a Maxwell Hamiltonian theory of matter combined with the quantum theory of atomistic polarization to obtain the electrodynamic dispersion of natural materials interacting with the photon field. They applied this theory to silicon and discovered the existence of anomalous atomistic waves. These waves occur in the spectral region where propagating waves are conventionally forbidden in a macroscopic theory. According […]
Light-driven molecular swing
Science Daily October 18, 2022 An international team of researchers (Germany, USA – UC Irvine) used electric-field-resolved spectroscopy and quantum-chemical modelling to precisely measure and describe the complete coherent energy transfer between octave-spanning mid-infrared waveforms and vibrating molecules in aqueous solution. The sub-optical-cycle temporal resolution of their technique revealed alternating absorption and (stimulated) emission on a few-femtosecond time scale. This behaviour can only be captured when effects beyond the rotating wave approximation are considered. At a femtosecond-to-picosecond timescale, optical-phase-dependent coherent transients, and the dephasing of the vibrations of resonantly excited methylsulfonylmethane (DMSO2) were observed. Ab initio modelling using density functional […]
A molecule of light and matter
Science Daily August 1, 2022 An international team of researchers (Austria, Germany) has observed a mechanical deformation of a cloud of ultracold 87Rb atoms due to the collective interplay of the atoms and a homogenous light field. This collective light scattering resulted in a self-confining potential with interesting features: It exhibited nonlocal properties, attractive for both red- and blue-detuned light fields and induced a remarkably strong force that depends on the gradient of the atomic density. In the article they discuss their experimental observations framework of a theoretical model based on a local-field approach for the light scattered by the […]
Researchers measure the binding state of light and matter for the first time
Phys.org August 1, 2022 Light-matter interaction is well understood on the single-atom level and routinely used to manipulate atomic gases. However, in denser ensembles, collective effects emerge that are caused by light-induced dipole-dipole interactions and multiple photon scattering. An international team of researchers (Austria, Germany) found a mechanical deformation of a cloud of ultracold 87Rb atoms due to the collective interplay of the atoms and a homogenous light field. The collective light scattering results in a self-confining potential which exhibits nonlocal properties, attractive for both red- and blue-detuned light fields and induces a remarkably strong force that depends on the […]