We show that the energy-transport efficiency in a chain of two-level emitters can be drastically enhancedby the presence of a photonic topological insulator (PTI). This is obtained by exploiting the peculiarproperties of its nonreciprocal surface plasmon polariton (SPP), which is unidirectional, and immune tobackscattering, and propagates in the bulk band gap. This amplification of transport efficiency can be asmuch as 2 orders of magnitude with respect to reciprocal SPPs. Moreover, we demonstrate that despite thepresence of considerable imperfections at the interface of the PTI, the efficiency of the SPP-assisted energytransport is almost unaffected by discontinuities. We also show that the SPP properties allow energytransport over considerably much larger distances than in the reciprocal case, and we point out aparticularly simple way to tune the transport. Finally, we analyze the specific case of a two-emitter chainand unveil the origin of the efficiency amplification. The efficiency amplification and the practicaladvantages highlighted in this work might be particularly useful in the development of new devicesintended to manage energy at the atomic scale.

Heat flux exchanged between two hot bodies at subwavelength separation distances can exceed the limitpredicted by the blackbody theory. However, this super-Planckian transfer is restricted to these separationdistances. Here we demonstrate the possible existence of a super-Planckian transfer at arbitrary large separationdistances if the interacting bodies are connected in the near field with weakly dissipating hyperbolic waveguides.This result opens the way to long-distance transport of near-field thermal energy.

We investigate the quantum optical torque on an atom interacting with an inhomogeneous electromagneticenvironment described by the most general linear constitutive relations. The atom is modeled as a two-levelsystem prepared in an arbitrary initial energy state. Using the Heisenberg equation of motion (HEM) and underthe Markov approximation, we show that the optical torque has a resonant and nonresonant part, associated,respectively, with a spontaneous-emission process and Casimir-type interactions with the quantum vacuum,which can both be written explicitly in terms of the system Green function. Our formulation is valid forany three-dimensional inhomogeneous, dissipative, dispersive, nonreciprocal, and bianisotropic structure. Weapply this general theory to a scenario in which the atom interacts with a material characterized by strongnonreciprocity and modal unidirectionality. In this case, the main decay channel of the atom energy is representedby the unidirectional surface waves launched at the nonreciprocal material-vacuum interface. To provide relevantphysical insight into the role of these unidirectional surface waves in the emergence of nontrivial optical torque,we derive closed-form expressions for the induced torque under the quasistatic approximation. Finally, weinvestigate the equilibrium states of the atom polarization, along which the atom spontaneously tends to aligndue to the action of the torque. Our theoretical predictions may be experimentally tested with cold Rydbergatoms and superconducting qubits near a nonreciprocal material. We believe that our general theory may findbroad application in the context of nanomechanical and biomechanical systems.

Based on the theory of macroscopic quantum electrodynamics, we generalize the expression of theCasimir force for nonreciprocal media. The essential ingredient of this result is the Green’s tensor betweentwo nonreciprocal semi-infinite slabs, including a reflexion matrix with four coefficients that mixes opticalpolarizations. This Green’s tensor does not obey Lorentz’s reciprocity and thus violates time-reversal symmetry.The general result for the Casimir force is analyzed in the retarded and nonretarded limits, concentrating on theinfluences arising from reflections with or without change of polarization. In a second step, we apply our generalresult to a photonic topological insulator whose nonreciprocity stems from an anisotropic permittivity tensor,namely InSb. We show that there is a regime for the distance between the slabs where the magnitude of theCasimir force is tunable by an external magnetic field. Furthermore, the strength of this tuning depends on theorientation of the magnetic field with respect to the slab surfaces.

We present a semi-analytical model of the resonance phenomena occurring in a hybrid system made of a 1D array of periodic subwavelength slits deposited on an insulator/graphene layer. We show that the spectral response of this hybrid system can be fully explained by a simple semi-analytical model based on weak and strong couplings between two elementary sub-systems.

Dye confinement into carbon nanotube significantly affects the electronic charge density distribution of the final hybrid system. Using the electron-phonon coupling sensitivity of the Raman G-band, we quantify experimentally how charge transfer from thiophene oligomers to single walled carbon nanotube is modulated by the diameter of the nano-container and its metallic or semiconducting character. This charge transfer is shown to restore the electron-phonon coupling into defected metallic nanotubes. For sub-nanometer diameter tube, an electron transfer optically activated is observed when the excitation energy matches the HOMO-LUMO transition of the confined oligothiophene. This electron doping accounts for an important enhancement of the photoluminescence intensity up to a factor of nearly six for optimal confinement configuration. This electron transfer shifts the Fermi level, acting on the photoluminescence efficiency. Therefore, thiophene oligomer encapsulation allows modulating the electronic structure and then the optical properties of the hybrid system.

The monomeric chlorophyll, Chl(D1), which is located between the PD1PD2 chlorophyll pair and the pheophytin, Pheo(D1), is the longest wavelength chlorophyll in the heart of Photosystem II and is thought to be the primary electron donor. Its central Mg2+ is liganded to a water molecule that is H-bonded to D1/T179. Here, two site-directed mutants, D1/T179H and D1/T179V, were made in the thermophilic cyanobacterium, Thermosynechococcus elongatus, and characterized by a range of biophysical techniques. The Mn4CaO5 cluster in the water-splitting site is fully active in both mutants. Changes in thermoluminescence indicate that i) radiative recombination occurs via the repopulation of *Chl(D1) itself; ii) non-radiative charge recombination reactions appeared to be faster in the T179H-PSII; and iii) the properties of PD1PD2 were unaffected by this mutation, and consequently iv) the immediate precursor state of the radiative excited state is the Chl(D1)(+)Pheo(D1)(-) radical pair. Chlorophyll bleaching due to high intensity illumination correlated with the amount of O-1(2) generated. Comparison of the bleaching spectra with the electrochromic shifts attributed to Chl(D1) upon Q(A)(-) formation, indicates that in the T179H-PSII and in the WT*3-PSII, the Chl(D1) itself is the chlorophyll that is first damaged by O-1(2), whereas in the T179V-PSII a more red chlorophyll is damaged, the identity of which is discussed. Thus, Chl(D1) appears to be one of the primary damage site in recombination-mediated photoinhibition. Finally, changes in the absorption of Chl(D1) very likely contribute to the well-known electrochromic shifts observed at similar to 430 nm during the S-state cycle.