arXiv subjects

D. J. Gosztola

Publications and source records attributed to D. J. Gosztola.

3 recordsLinked to original sources

arXiv2020

The effect of periodic spatial perturbations on the emission rates of quantum dots near graphene platforms

Quenching of fluorescence (FL) at the vicinity of conductive surfaces, and in particular, near a 2-D graphene layer has become an important biochemical sensing tool. The quenching is attributed to fast non-radiative energy transfer between a chromophore and the lossy conductor. Increased emission rate is also observed when the chromophore is coupled to a resonator. Here we combine the two effects in order to control the emission lifetime of the chromophore. In our case, the resonator was defined by an array of nano-holes in the oxide substrate underneath a graphene surface guide. We demonstrated an emission rate change by more than 50% as the sample was azimuthally rotated with respect to the polarization of the excitation laser. Such control over the emission life-time could be used to control resonance energy transfer (RET) between two chromophores.

cond-mat.mes-hall↗

arXiv2018

Spectroscopic fingerprints of many-body renormalizations in$1T$-TiSe$_2$

We have employed high resolution angle resolved photoemission spectroscopy (ARPES) measurements to investigate many-body renormalizations of the single-particle excitations in $1T$-TiSe$_2$. The energy distribution curves of the ARPES data reveal intrinsic peak-dip-hump feature, while the electronic dispersion derived from the momentum distribution curves of the data highlights, for the first time, multiple kink structures. These are canonical signatures of a coupling between the electronic degrees of freedom and some Bosonic mode in the system. We demonstrate this using a model calculation of the single-particle spectral function at the presence of an electron-Boson coupling. From the self-energy analysis of our ARPES data, we discern some of the critical energy scales of the involved Bosonic mode, which are $\sim$15 and 26 meV. Based on a comparison between these energies and the characteristic energy scales of our Raman scattering data, we identify these Bosonic modes as Raman active breathing (${\text{A}}_\text{1g}$) and shear (${\text{E}}_\text{g}$) modes, respectively. Direct observation of the band-renormalization due to electron-phonon coupling increases the possibility that electron-phonon interactions are central to the collective quantum states such as charge density wave (CDW) and superconductivity in the compounds based on $1T$-TiSe$_2$.

cond-mat.str-el↗

arXiv2016

Nano-optical imaging of WSe2 waveguide modes revealing light-exciton interactions

We report on nano-optical imaging study of WSe2 thin flakes with the scanning near-field optical microscopy (NSOM). The NSOM technique allows us to visualize in real space various waveguide photon modes inside WSe2. By tuning the excitation laser energy, we are able to map the entire dispersion of these waveguide modes both above and below the A exciton energy of WSe2. We found that all the modes interact strongly with WSe2 excitons. The outcome of the interaction is that the observed waveguide modes shift to higher momenta right below the A exciton energy. At higher energies, on the other hand, these modes are strongly damped due to adjacent B excitons or band edge absorptions. The mode-shifting phenomena are consistent with polariton formation in WSe2.

cond-mat.mes-hall↗