@article{ScharfBraggioStambinietal.2020, author = {Scharf, Benedikt and Braggio, Alessandro and Stambini, Elia and Giazotto, Francesco and Hankiewicz, Ewelina M.}, title = {Topological Josephson heat engine}, series = {Communications Physics}, volume = {3}, journal = {Communications Physics}, doi = {10.1038/s42005-020-00463-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230603}, year = {2020}, abstract = {Topological superconductors represent a fruitful playing ground for fundamental research as well as for potential applications in fault-tolerant quantum computing. Especially Josephson junctions based on topological superconductors remain intensely studied, both theoretically and experimentally. The characteristic property of these junctions is their 4-periodic ground-state fermion parity in the superconducting phase difference. Using such topological Josephson junctions, we introduce the concept of a topological Josephson heat engine. We discuss how this engine can be implemented as a Josephson-Stirling cycle in topological superconductors, thereby illustrating the potential of the intriguing and fruitful marriage between topology and coherent thermodynamics. It is shown that the Josephson-Stirling cycle constitutes a highly versatile thermodynamic machine with different modes of operation controlled by the cycle temperatures. Finally, the thermodynamic cycle reflects the hallmark 4 pi -periodicity of topological Josephson junctions and could therefore be envisioned as a complementary approach to test topological superconductivity. Topological superconductors are expected to be a key component of quantum computing systems but reliably detecting their exotic properties is a challenge. Here, the authors propose a topological Josephson heat engine which uses thermodynamic effects to probe the 4 pi -periodic ground state of a topological superconductor.}, language = {en} } @article{MaistrenkoScharfManskeetal.2021, author = {Maistrenko, Oleksii and Scharf, Benedikt and Manske, Dirk and Hankiewicz, Ewelina M.}, title = {Planar Josephson Hall effect in topological Josephson junctions}, series = {Physical Review B}, volume = {103}, journal = {Physical Review B}, doi = {10.1103/PhysRevB.103.054508}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-370139}, year = {2021}, abstract = {Josephson junctions based on three-dimensional topological insulators offer intriguing possibilities to realize unconventional 𝑝-wave pairing and Majorana modes. Here, we provide a detailed study of the effect of a uniform magnetization in the normal region: We show how the interplay between the spin-momentum locking of the topological insulator and an in-plane magnetization parallel to the direction of phase bias leads to an asymmetry of the Andreev spectrum with respect to transverse momenta. If sufficiently large, this asymmetry induces a transition from a regime of gapless, counterpropagating Majorana modes to a regime with unprotected modes that are unidirectional at small transverse momenta. Intriguingly, the magnetization-induced asymmetry of the Andreev spectrum also gives rise to a Josephson Hall effect, that is, the appearance of a transverse Josephson current. The amplitude and current phase relation of the Josephson Hall current are studied in detail. In particular, we show how magnetic control and gating of the normal region can enable sizable Josephson Hall currents compared to the longitudinal Josephson current. Finally, we also propose in-plane magnetic fields as an alternative to the magnetization in the normal region and discuss how the planar Josephson Hall effect could be observed in experiments.}, language = {en} } @article{ElsterPlattThomaleetal.2015, author = {Elster, Lars and Platt, Christian and Thomale, Ronny and Hanke, Werner and Hankiewicz, Ewelina M.}, title = {Accessing topological superconductivity via a combined STM and renormalization group analysis}, series = {Nature Communications}, volume = {6}, journal = {Nature Communications}, number = {8232}, doi = {10.1038/ncomms9232}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148181}, year = {2015}, abstract = {The search for topological superconductors has recently become a key issue in condensed matter physics, because of their possible relevance to provide a platform for Majorana bound states, non-Abelian statistics, and quantum computing. Here we propose a new scheme which links as directly as possible the experimental search to a material-based microscopic theory for topological superconductivity. For this, the analysis of scanning tunnelling microscopy, which typically uses a phenomenological ansatz for the superconductor gap functions, is elevated to a theory, where a multi-orbital functional renormalization group analysis allows for an unbiased microscopic determination of the material-dependent pairing potentials. The combined approach is highlighted for paradigmatic hexagonal systems, such as doped graphene and water-intercalated sodium cobaltates, where lattice symmetry and electronic correlations yield a propensity for a chiral singlet topological superconductor. We demonstrate that our microscopic material-oriented procedure is necessary to uniquely resolve a topological superconductor state.}, language = {en} } @article{BrueneThienelStuiberetal.2014, author = {Br{\"u}ne, Christoph and Thienel, Cornelius and Stuiber, Michael and B{\"o}ttcher, Jan and Buhmann, Hartmut and Novik, Elena G. and Liu, Chao-Xing and Hankiewicz, Ewelina M. and Molenkamp, Laurens W.}, title = {Dirac-Screening Stabilized Surface-State Transport in a Topological Insulator}, series = {Physical Review X}, volume = {4}, journal = {Physical Review X}, number = {4}, issn = {2160-3308}, doi = {10.1103/PhysRevX.4.041045}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-118091}, pages = {041045}, year = {2014}, abstract = {We report magnetotransport studies on a gated strained HgTe device. This material is a three-dimensional topological insulator and exclusively shows surface-state transport. Remarkably, the Landau-level dispersion and the accuracy of the Hall quantization remain unchanged over a wide density range (3×1011  cm-2