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Register a new userNegative refraction in the relativistic electron gas
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We show that a gas of relativistic electrons is a left-handed material at low frequencies by computing the effective electric permittivity and effective magnetic permeability that appear in Maxwells equations in terms of the responses appearing in the constitutive relations, and showing that the former are both negative below the {it same} frequency, which coincides with the zero-momentum frequency of longitudinal plasmons. We also show, by explicit computation, that the photonic mode of the electromagnetic radiation does not dissipate energy, confirming that it propagates in the gas with the speed of light in vacuum, and that the medium is transparent to it. We then combine those results to show that the gas has a negative effective index of refraction $n_{rm eff}=-1$. We illustrate the consequences of this fact for Snells law, and for the reflection and transmission coefficients of the gas.
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We investigate the dispersion of a classical electromagnetic field in a relativistic ideal gas of charged bosons using scalar quantum electrodynamics at finite temperature and charge density. We derive the effective electromagnetic responses and the electromagnetic propagation modes that characterize the gas as a left-handed material with negative effective index of refraction $n_{rm eff}=-1$ below the transverse plasmon frequency. In the condensed phase, we show that the longitudinal plasmon dispersion relation exhibits a roton-type local minimum that disappears at the transition temperature.
Ultracold atoms in optical lattices provide a unique opportunity to study Bose- Hubbard physics. In this work we show that by considering a spatially varying onsite interaction it is possible to manipulate the motion of excitations above the Mott phase in a Bose-Hubbard system. Specifically, we show that it is possible to engineer regimes where excitations will negatively refract, facilitating the construction of a flat lens.
We have studied the electrical conductivity of the electron gas in parallel electric and magnetic fields directed along the plane of a parabolic quantum well (across the profile of the potential). We found a general expression for the electrical conductivity applicable for any magnitudes of the magnetic field and the degree of degeneration of the electron gas. A new mechanism of generation of the negative magnetoresistance has been revealed. It has been shown that in a parabolic quantum well with a non-degenerated electron gas the negative magnetoresistance results from spin splitting of the levels of the size quantization.
We analyze different factors which influence the negative refraction in solids and multi-atom molecules. We find that this negative refraction is significantly influenced by simultaneous multi-electron transitions with the same transition frequency and dipole redistribution over different eigenstates. We show that these simultaneous multi-electron transitions and enhanced transition dipole broaden the bandwidth of the negative refraction by at least one order of magnitude. This work provides additional connection between metamaterials and Mobius strips.
It is generally believed that Veselagos criterion for negative refraction cannot be fulfilled in natural materials. However, considering imaginary parts of the permittivity ({epsilon}) and permeability ({mu}) and for metals at not too high frequencies the general condition for negative refraction becomes extremely simple: Re({mu}) < 0 --> Re(n) < 0. Here we demonstrate experimentally that in such natural metals as pure Co and FeCo alloy the negative values of the refractive index are achieved close to the frequency of the ferromagnetic resonance. Large values of the negative refraction can be obtained at room temperature and they can easily be tuned in moderate magnetic fields.
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