Arijit Kundu

Transport Signatures of Floquet Majorana Fermions in Driven Topological Superconductors

Floquet Majorana fermions are steady states of equal superposition of electrons and holes in a periodically driven superconductor. We study the experimental signatures of Floquet Majorana fermions in transport measurements and show, both analytically and numerically, that their presence is signaled by a quantized conductance sum rule over discrete values of lead bias differing by multiple absorption or emission energies at drive frequency. We also study the effects of static disorder and find that the quantized sum rule is robust against weak disorder. Thus, we offer a unique way to identify the topological signatures of Floquet Majorana fermions.

Effective theory of Floquet topological transitions.

We develop a theory of topological transitions in a Floquet topological insulator, using graphene irradiated by circularly polarized light as a concrete realization. We demonstrate that a hallmark signature of such transitions in a static system, i.e., metallic bulk transport with conductivity of order e^{2}/h, is substantially suppressed at some Floquet topological transitions in the clean system. We determine the conditions for this suppression analytically and confirm our results in numerical simulations. Remarkably, introducing disorder dramatically enhances this transport by several orders of magnitude.

Electron-phonon scattering in topological insulator thin films

We present a theoretical study of electron-phonon scattering effects in thin films made of a strong topological insulator. Phonons are modelled by isotropic elastic continuum theory with stress-free boundary conditions, and the interaction with the helical surface Dirac fermions is mediated by the deformation potential. We determine the temperature-dependent electrical resistivity

Anomalous Josephson current, incipient time-reversal symmetry breaking, and Majorana bound states in interacting multilevel dots

\rho(T)

Floquet-Engineered Valleytronics in Dirac Systems

and the quasiparticle decay rate

Tunable Floquet Majorana fermions in driven coupled quantum dots

\Gamma(T)

Magnetic scattering of Dirac fermions in topological insulators and graphene

observable in photoemission. The low- and high-temperature power laws for both quantities are obtained analytically. Detailed estimates covering the full temperature range are provided for Bi

Proximity-induced superconductivity in Weyl semimetals

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Chiral nodes and oscillations in the Josephson current in Weyl semimetals

Se

0-π transitions in a Josephson junction of an irradiated Weyl semimetal

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