53 research outputs found
Resonantly Tunable Majorana Polariton in a Microwave Cavity
We study the spectrum of a one-dimensional Kitaev chain placed in a microwave
cavity. In the off-resonant regime, the frequency shift of the cavity can be
used to identify the topological phase transition of the coupled system. In the
resonant regime, the topology of the system can be controlled via the microwave
cavity occupation and, moreover, for a large number of photons (classical
limit), the physics becomes similar to that of periodically-driven systems
(Floquet insulators). We also analyze numerically a finite chain and show the
existence of a degenerate subspace in the presence of the cavity that can be
interpreted as a \textit{Majorana polariton}.Comment: 11 pages, 6 figure
Photon assisted braiding of Majorana fermions in a cavity
We study the dynamical process of braiding Majorana bound states in the
presence of the coupling to photons in a microwave cavity. We show
theoretically that the phase associated with the braiding of Majoranas,
as well as the parity of the ground state are imprinted into the photonic field
of the cavity, which can be detected by dispersive readouts techniques. These
manifestations are purely dynamical, they occur in the absence of any splitting
of the MBS that are exchanged, and they disappear in the static setups studied
previously. Conversely, the cavity can affect the braiding phase, which in turn
should allow for cavity controlled braiding.Comment: 4.5 pages+7 pages supplementary material, 4 figure
Acoustic phonons and strain in core/shell nanowires
We study theoretically the low-energy phonons and the static strain in
cylindrical core/shell nanowires (NWs). Assuming pseudomorphic growth,
isotropic media, and a force-free wire surface, we derive algebraic expressions
for the dispersion relations, the displacement fields, and the stress and
strain components from linear elasticity theory. Our results apply to NWs with
arbitrary radii and arbitrary elastic constants for both core and shell. The
expressions for the static strain are consistent with experiments, simulations,
and previous analytical investigations; those for phonons are consistent with
known results for homogeneous NWs. Among other things, we show that the
dispersion relations of the torsional, longitudinal, and flexural modes change
differently with the relative shell thickness, and we identify new terms in the
corresponding strain tensors that are absent for uncapped NWs. We illustrate
our results via the example of Ge/Si core/shell NWs and demonstrate that
shell-induced strain has large effects on the hole spectrum of these systems.Comment: 21 pages, 5 figure
Controlling topological superconductivity by magnetization dynamics
We study theoretically a chain of precessing classical magnetic impurities in
an -wave superconductor. Utilizing a rotating wave description, we derive an
effective Hamiltonian that describes the emergent Shiba band. We find that this
Hamiltonian shows non-trivial topological properties, and we obtain the
corresponding topological phase diagrams both numerically and analytically. We
show that changing the precession frequency offers a control over topological
phase transitions and the emergence of Majorana bound states. We propose
driving the magnetic impurities or magnetic texture into precession by means of
spin-transfer torque in a spin-Hall setup, and manipulate it using spin
superfluidity in the case of planar magnetic order.Comment: 5 pages+9 pages supplementary materia
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