TY  - JOUR
A1  - Scharf, Benedikt
A1  - Braggio, Alessandro
A1  - Stambini, Elia
A1  - Giazotto, Francesco
A1  - Hankiewicz, Ewelina M.
T1  - Topological Josephson heat engine
JF  - Communications Physics
N2  - 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.
KW  - superconductivity
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230603
VL  - 3
ER  - 
TY  - JOUR
A1  - Brüne, Christoph
A1  - Thienel, Cornelius
A1  - Stuiber, Michael
A1  - Böttcher, Jan
A1  - Buhmann, Hartmut
A1  - Novik, Elena G.
A1  - Liu, Chao-Xing
A1  - Hankiewicz, Ewelina M.
A1  - Molenkamp, Laurens W.
T1  - Dirac-Screening Stabilized Surface-State Transport in a Topological Insulator
JF  - Physical Review X
N2  - 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<n<2×1012  cm−2). These observations imply that even at large carrier densities, the transport is surface-state dominated, where bulk transport would have been expected to coexist already. Moreover, the density dependence of the Dirac-type quantum Hall effect allows us to identify the contributions from the individual surfaces. A k⋅p model can describe the experiments but only when assuming a steep band bending across the regions where the topological surface states are contained. This steep potential originates from the specific screening properties of Dirac systems and causes the gate voltage to influence the position of the Dirac points rather than that of the Fermi level.
KW  - condensed matter physics
KW  - topological insulators
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-118091
SN  - 2160-3308
VL  - 4
IS  - 4
ER  - 
TY  - JOUR
A1  - Elster, Lars
A1  - Platt, Christian
A1  - Thomale, Ronny
A1  - Hanke, Werner
A1  - Hankiewicz, Ewelina M.
T1  - Accessing topological superconductivity via a combined STM and renormalization group analysis
JF  - Nature Communications
N2  - 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.
KW  - tunneling spectroscopy
KW  - Sr\(_2\)RuO\(_4\)
KW  - states
KW  - transition
KW  - insulators
KW  - surface
KW  - Majorana fermions
KW  - unconventional superconductivity
KW  - wave superconductors
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148181
VL  - 6
IS  - 8232
ER  -