Martin Dressel

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Studies of the electromagnetic response of various classes of correlated electron materials including transition-metal oxides, organic and molecular conductors, intermetallic compounds with d and f electrons, as well as magnetic semiconductors are reviewed. Optical inquiry into correlations in all these diverse systems is enabled by experimental access to(More)
Using data collected by the HERA-B experiment, we have measured the fraction of J/ψ's produced via radiative χ c decays in interactions of 920 GeV protons with carbon and titanium targets. We obtained R χ c = 0. fraction of J/ψ from χ c decays averaged over proton–carbon and proton–titanium collisions. This result is in agreement with previous measurements(More)
Controlling the dynamics of spins on surfaces is pivotal to the design of spintronic and quantum computing devices. Proposed schemes involve the interaction of spins with graphene to enable surface-state spintronics and electrical spin manipulation. However, the influence of the graphene environment on the spin systems has yet to be unravelled. Here we(More)
The electrical conduction of metals is governed by how freely mobile electrons can move throughout the material. This movement is hampered by scattering with other electrons, as well as with impurities or thermal excitations (phonons). Experimentally, the scattering processes of single electrons are not observed, but rather the overall response of all(More)
We observe charge-order fluctuations in the quasi-two-dimensional organic superconductor β''-(BEDT-TTF)2SF5CH2CF2SO3, both by means of vibrational spectroscopy, locally probing the fluctuating charge order, and by investigating the in-plane dynamical response by infrared reflectance spectroscopy. The decrease of the effective electronic interaction in an(More)
Interacting conduction electrons are usually described within Fermi-liquid theory, which states that, in spite of strong interactions, the low-energy excitations are electron-like quasiparticles with charge and spin. In recent years there has been tremendous interest in conducting systems that are not Fermi liquids, motivated by the observation of highly(More)
We studied the magnetic and electronic properties of the insulating charge-transfer salt (TMTTF) 2 AsF 6 by electron spin resonance (ESR), SQUID magnetometer and optical conductivity measurements. For the first time, the lattice dynamics was investigated in the vicinity of the charge order transition. We found a splitting of the electron-molecular-vibration(More)
We measure the ultrafast recombination of photoexcited quasiparticles (holon-doublon pairs) in the one dimensional Mott insulator ET-F(2)TCNQ as a function of external pressure, which is used to tune the electronic structure. At each pressure value, we first fit the static optical properties and extract the electronic bandwidth t and the intersite(More)