arXiv subjects

David Hagenmüller

Publications and source records attributed to David Hagenmüller.

23 records · Page 2Linked to original sources

arXiv2018

Cavity-assisted mesoscopic transport of fermions: Coherent and dissipative dynamics

We study the interplay between charge transport and light-matter interactions in a confined geometry, by considering an open, mesoscopic chain of two-orbital systems resonantly coupled to a single bosonic mode close to its vacuum state. We introduce and benchmark different methods based on self-consistent solutions of non-equilibrium Green's functions and numerical simulations of the quantum master equation, and derive both analytical and numerical results. It is shown that in the dissipative regime where the cavity photon decay rate is the largest parameter, the light-matter coupling is responsible for a steady-state current enhancement scaling with the cooperativity parameter. We further identify different regimes of interest depending on the ratio between the cavity decay rate and the electronic bandwidth. Considering the situation where the lower band has a vanishing bandwidth, we show that for a high-finesse cavity, the properties of the resonant Bloch state in the upper band are transfered to the lower one, giving rise to a delocalized state along the chain. Conversely, in the dissipative regime with low cavity quality factors, we find that the current enhancement is due to a collective decay of populations from the upper to the lower band.

quant-ph↗

arXiv2017

Cavity-enhanced transport of charge

We theoretically investigate charge transport through electronic bands of a mesoscopic one-dimensional system, where inter-band transitions are coupled to a confined cavity mode, initially prepared close to its vacuum. This coupling leads to light-matter hybridization where the dressed fermionic bands interact via absorption and emission of dressed cavity-photons. Using a self-consistent non-equilibrium Green's function method, we compute electronic transmissions and cavity photon spectra and demonstrate how light-matter coupling can lead to an enhancement of charge conductivity in the steady-state. We find that depending on cavity loss rate, electronic bandwidth, and coupling strength, the dynamics involves either an individual or a collective response of Bloch states, and explain how this affects the current enhancement. We show that the charge conductivity enhancement can reach orders of magnitudes under experimentally relevant conditions.

quant-ph↗

arXiv2012

Ultrastrong coupling of the cyclotron transition of a two-dimensional electron gas to a THz metamaterial

Artificial cavity photon resonators with ultrastrong light-matter interactions are attracting interest both in semiconductor and superconducting systems, due to the possibility of manipulating the cavity quantum electrodynamic ground state with controllable physical properties. We report here experiments showing ultrastrong light-matter coupling in a terahertz metamaterial where the cyclotron transition of a high mobility two-dimensional electron gas is coupled to the photonic modes of an array of electronic split-ring resonators. We observe a normalized coupling ratio $\fracΩ{ω_c}=0.58$ between the vacuum Rabi frequency $Ω$ and the cyclotron frequency $ω_c$. Our system appears to be scalable in frequency and could be brought to the microwave spectral range with the potential of strongly controlling the magnetotransport properties of a high-mobility 2DEG.

cond-mat.mes-hall↗

arXiv2011

Cavity QED of the graphene cyclotron transition

We investigate theoretically the cavity quantum electrodynamics of the cyclotron transition for Dirac fermions in graphene. We show that the ultrastrong coupling regime characterized by a vacuum Rabi frequency comparable or even larger than the transition frequency can be obtained for high enough filling factors of the graphene Landau levels. Important qualitative differences occur with respect to the corresponding physics of massive electrons in a semiconductor quantum well. In particular, an instability for the ground state analogous to the one occuring in the Dicke-model is predicted for increasing value of the electron density.

cond-mat.mes-hall↗

arXiv2010

Ultrastrong coupling between a cavity resonator and the cyclotron transition of a 2D electron gas in the case of integer filling factor

We investigate theoretically the coupling between a cavity resonator and the cyclotron transition of a two dimensional electron gas under an applied perpendicular magnetic field. We derive and diagonalize an effective quantum Hamiltonian describing the magnetopolariton excitations of the two dimensional electron gas for the case of integer filling factors. The limits of validity of the present approach are critically discussed. The dimensionless vacuum Rabi frequency $Ω_0/ω_0$ (i.e., normalized to the cyclotron frequency $ω_0$) is shown to scale as $\sqrt{α\: n_{QW} ν}$, where $α$ is the fine structure constant, $n_{QW}$ is the number of quantum wells and $ν$ is the filling factor in each well. We show that with realistic parameters of a high-mobility semiconductor two dimensional electron gas, the dimensionless coupling $Ω_0/ω_0$ can be much larger than 1 in the case of $ν\gg 1$, the latter condition being typically realized for cyclotron transitions in the microwave range. Implications of such ultrastrong coupling regime are discussed.

cond-mat.other↗