15 research outputs found
Testing the Renormalization of the von Klitzing Constant by Cavity Vacuum Fields
In light of recent developments demonstrating the impact of cavity vacuum
fields inducing the breakdown of topological protection in the integer quantum
Hall effect, a compelling question arises: what effects might cavity vacuum
fields have on fundamental constants in solid-state systems? In this work we
present an experiment that assesses the possibility of the von Klitzing
constant itself being modified. By employing a Wheatstone bridge, we precisely
measure the difference between the quantized Hall resistance of a
cavity-embedded Hall bar and the resistance standard, achieving an accuracy
down to 1 part in 105 for the lowest Landau level. While our results do not
suggest any deviation that could imply a modified Hall resistance, our work
represents pioneering efforts in exploring the fundamental implications of
vacuum fields in solid-state systems
Landau polaritons in highly non-parabolic 2D gases in the ultra-strong coupling regime
We probe ultra-strong light matter coupling between metallic terahertz
metasurfaces and Landau-level transitions in high mobility 2D electron and hole
gases. We utilize heavy-hole cyclotron resonances in strained Ge and electron
cyclotron resonances in InSb quantum wells, both within highly non-parabolic
bands, and compare our results to well known parabolic AlGaAs/GaAs quantum well
(QW) systems. Tuning the coupling strength of the system by two methods,
lithographically and by optical pumping, we observe a novel behavior clearly
deviating from the standard Hopfield model previously verified in cavity
quantum electrodynamics: an opening of a lower polaritonic gap
High-Tc superconducting metasurfaces for ultra-strong coupling experiments at THz frequencies
THz Ultrastrong Coupling in an Engineered Fabry-Perot Cavity
We report a monolithic THz planar Fabry-Perot cavity fabricated with wafer bonding and provided with metallic mirrors with subwavelength apertures. We demonstrate its coupling to the cyclotron resonance of a high-mobility, two-dimensional electron gas. Q factors up to 89 are observed for the first mode at similar or equal to 300 GHz, with cooperativity C = 56.4 and a normalized coupling ratio Omega/omega in the first mode of up to 17.5% and the third mode of up to 6.4%.ISSN:2330-402
High T_c Superconducting THz Metamaterial for Ultrastrong Coupling in a Magnetic Field
ISSN:2330-402
Breakdown of topological protection by cavity vacuum fields in the integer quantum Hall effect
The prospect of controlling the electronic properties of materials via the vacuum fields of cavity electromagnetic resonators is emerging as one of the frontiers of condensed matter physics. We found that the enhancement of vacuum field fluctuations in subwavelength split-ring resonators strongly affects one of the most paradigmatic quantum protectorates, the quantum Hall electron transport in high-mobility two-dimensional electron gases. The observed breakdown of the topological protection of the integer quantum Hall effect is interpreted in terms of a long-range cavity-mediated electron hopping where the anti-resonant terms of the light-matter coupling Hamiltonian develop into a finite resistivity induced by the vacuum fluctuations. Our experimental platform can be used for any two-dimensional material and provides a route to manipulate electron phases in matter by means of vacuum-field engineering.ISSN:0036-8075ISSN:1095-920