77 research outputs found
Teleportation-induced entanglement of two nanomechanical oscillators coupled to a topological superconductor
A one-dimensional topological superconductor features a single fermionic zero
mode that is delocalized over two Majorana bound states located at the ends of
the system. We study a pair of spatially separated nanomechanical oscillators
tunnel-coupled to these Majorana modes. Most interestingly, we demonstrate that
the combination of electron-phonon coupling and a finite charging energy on the
mesoscopic topological superconductor can lead to an effective superexchange
between the oscillators via the non-local fermionic zero mode. We further show
that this teleportation mechanism leads to entanglement of the two oscillators
over distances that can significantly exceed the coherence length of the
superconductor.Comment: 6 page
Dynamical Topological Order Parameters far from Equilibrium
We introduce a topological quantum number -- coined dynamical topological
order parameter (DTOP) -- that is dynamically defined in the real-time
evolution of a quantum many-body system and represented by a momentum space
winding number of the Pancharatnam geometric phase. Our construction goes
conceptually beyond the standard notion of topological invariants
characterizing the wave-function of a system, which are constants of motion
under coherent time evolution. In particular, we show that the DTOP can change
its integer value at discrete times where so called dynamical quantum phase
transitions occur, thus serving as a dynamical analog of an order parameter.
Interestingly, studying quantum quenches in one-dimensional two-banded
Bogoliubov de Gennes models, we find that the DTOP is capable of resolving if
the topology of the system Hamiltonian has changed over the quench.
Furthermore, we investigate the relation of the DTOP to the dynamics of the
string order parameter that characterizes the topology of such systems in
thermal equilibrium
Non-Hermitian Weyl Physics in Topological Insulator Ferromagnet Junctions
We introduce and investigate material junctions as a generic and tuneable
electronic platform for the realization of exotic non-Hermitian (NH)
topological states of matter, where the NH character is induced by the surface
self-energy of a thermal reservoir. As a conceptually rich and immediately
experimentally realizable example, we consider a three-dimensional topological
insulator (TI) coupled to a ferromagnetic lead. Remarkably, the symmetry
protected TI is promoted in a dissipative fashion to a non-symmetry protected
NH Weyl phase with no direct Hermitian counterpart and which exhibits
robustness against any perturbation. The transition between a gapped phase and
the NH Weyl phase may be readily tuned experimentally with the magnetization
direction of the ferromagnetic lead. Given the robustness of this exotic nodal
phase, our general analysis also applies to, e.g., a two-dimensional electron
gas close to criticality in proximity to a ferromagnetic lead. There, the
predicted bulk Fermi arcs are directly amenable to surface spectroscopy methods
such as angle-resolved photoemission spectroscopy.Comment: 6 pages, 4 figure
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