Prof Dieter Jaksch

Abstract:

We investigate electron paring in a two-dimensional electron system mediated by vacuum fluctuations inside a nanoplasmonic terahertz cavity. We show that the structured cavity vacuum can induce long-range attractive interactions between current fluctuations which lead to pairing in generic materials with critical temperatures in the low-kelvin regime for realistic parameters. The induced state is a pair-density wave superconductor which can show a transition from a fully gapped to a partially gapped phase—akin to the pseudogap phase in high-Tc superconductors. Our findings provide a promising tool for engineering intrinsic electron interactions in two-dimensional materials.

Abstract:

© 2019 American Physical Society. The interaction Hamiltonian (Formula Presented) Eq. (14) describing the interaction between the cavity and the electronic system was obtained by expanding the Peierls Hamiltonian in Eq. (A4) up to first order in the small parameter (Formula Presented) All results presented in the paper are consistent with this appro imate interaction Hamiltonian, leading to an effective Hamiltonian that depends quadratically on. However, it turns out that a straightforward improvement of the parameters entering the effective Hamiltonian in Eq. (26) can be obtained by including the second-order term in the Peierls Hamiltonian in Eq. (A4). This term gives rise to modifications of our results that are also of order through a renormalization of the nearest-neighbor hopping amplitude (Formula Presented) The authors would like to thank M. A. Sentef for bringing the importance of the second-order term in Eq. (A4) to our attention.

Abstract:

We investigate the ground-state properties of a bosonic Harper-Hofstadter model with local interactions on a finite cylindrical lattice with filling fraction ν = 1/2. We find that our system supports topologically ordered states by calculating the topological entanglement entropy, and its value is in good agreement with the theoretical value for the ν = 1/2 Laughlin state. By exploring the behavior of the density profiles, edge currents, and singleparticle correlation functions, we find that the ground state on the cylinder shows all signatures of a fractional quantum Hall state even for large values of the magnetic flux density. Furthermore, we determine the dependence of the correlation functions and edge currents on the interaction strength. We find that depending on the magnetic flux density, the transition toward Laughlin-like behavior can be either smooth or it can happen abruptly for some critical interaction strength