Parafermion braiding in fractional quantum Hall edge states with a finite chemical potential

in Physical Review. B, Condensed Matter and Materials Physics (2019), 100

Parafermions are non-Abelian anyons which generalize Majorana fermions and hold great promise for topological quantum computation. We study the braiding of Z2n parafermions which have been predicted to ... [more ▼]

Parafermions are non-Abelian anyons which generalize Majorana fermions and hold great promise for topological quantum computation. We study the braiding of Z2n parafermions which have been predicted to emerge as localized zero modes in fractional quantum Hall systems at filling factor ν=1/n (n odd). Using a combination of bosonization and refermionization, we calculate the energy splitting as a function of distance and chemical potential for a pair of parafermions separated by a gapped region. Braiding of parafermions in quantum Hall edge states can be implemented by repeated fusion and nucleation of parafermion pairs. We simulate the conventional braiding protocol of parafermions numerically, taking into account the finite separation and finite chemical potential. We show that a nonzero chemical potential poses challenges for the adiabaticity of the braiding process because it leads to accidental crossings in the spectrum. To remedy this, we propose an improved braiding protocol which avoids those degeneracies. [less ▲]

Entropy production in one-dimensional quantum fluids

in Physical Review. B (2019)

Disorder-driven exceptional lines and Fermi ribbons in tilted nodal-line semimetals

in Physical Review. B, Condensed Matter (2019), 99

We consider the impact of disorder on the spectrum of three-dimensional nodal-line semimetals. We show that the combination of disorder and a tilted spectrum naturally leads to a non-Hermitian self-energy ... [more ▼]

We consider the impact of disorder on the spectrum of three-dimensional nodal-line semimetals. We show that the combination of disorder and a tilted spectrum naturally leads to a non-Hermitian self-energy contribution that can split a nodal line into a pair of exceptional lines. These exceptional lines form the boundary of an open and orientable bulk Fermi ribbon in reciprocal space on which the energy gap vanishes. We find that the orientation and shape of such a disorder-induced bulk Fermi ribbon is controlled by the tilt direction and the disorder properties, which can also be exploited to realize a twisted bulk Fermi ribbon with nontrivial winding number. Our results put forward a paradigm for the exploration of non-Hermitian topological phases of matter. [less ▲]

Z4 parafermions in one-dimensional fermionic lattices

in Physical Review. B, Condensed Matter (2018), 98

Parafermions are emergent excitations which generalize Majorana fermions and are potentially relevant to topological quantum computation. Using the concept of Fock parafermions, we present a mapping ... [more ▼]

Parafermions are emergent excitations which generalize Majorana fermions and are potentially relevant to topological quantum computation. Using the concept of Fock parafermions, we present a mapping between lattice Z4-parafermions and lattice spin-1/2 fermions which preserves the locality of operators with Z4 symmetry. Based on this mapping, we construct an exactly solvable, local one-dimensional fermionic Hamiltonian which hosts parafermionic edge states. We numerically show that the parafermionic phase remains stable in a wide range of parameters, and discuss its signatures in the fermionic spectral function. [less ▲]

Universal scaling of quench-induced correlations in a one-dimensional channel at finite temperature

in SciPost Physics (2018)

It has been shown that a quantum quench of interactions in a one-dimensional fermion system at zero temperature induces a universal power law ∝t−2 in its long-time dynamics. In this paper we demonstrate ... [more ▼]

It has been shown that a quantum quench of interactions in a one-dimensional fermion system at zero temperature induces a universal power law ∝t−2 in its long-time dynamics. In this paper we demonstrate that this behaviour is robust even in the presence of thermal effects. The system is initially prepared in a thermal state, then at a given time the bath is disconnected and the interaction strength is suddenly quenched. The corresponding effects on the long times dynamics of the non-equilibrium fermionic spectral function are considered. We show that the non-universal power laws, present at zero temperature, acquire an exponential decay due to thermal effects and are washed out at long times, while the universal behaviour ∝t−2 is always present. To verify our findings, we argue that these features are also visible in transport properties at finite temperature. The long-time dynamics of the current injected from a biased probe exhibits the same universal power law relaxation, in sharp contrast with the non-quenched case which features a fast exponential decay of the current towards its steady value, and thus represents a fingerprint of quench-induced dynamics. Finally, we show that a proper tuning of the probe temperature, compared to that of the one-dimensional channel, can enhance the visibility of the universal power-law behaviour. [less ▲]

Quantum thermodynamics of the resonant-level model with driven system-bath coupling

in Physical Review. B, Condensed Matter (2018), 97

Magnetotransport signatures of three-dimensional topological insulator nanostructures

in Physical Review. B (2018), 97(24), 245429

We study the magnetotransport properties of patterned 3D topological insulator nanostructures with several leads, such as kinks or Y-junctions, near the Dirac point with analytical as well as numerical ... [more ▼]

We study the magnetotransport properties of patterned 3D topological insulator nanostructures with several leads, such as kinks or Y-junctions, near the Dirac point with analytical as well as numerical techniques. The interplay of the nanostructure geometry, the external magnetic field, and the spin-momentum locking of the topological surface states lead to a richer magnetoconductance phenomenology as compared to straight nanowires. Similar to straight wires, a quantized conductance with perfect transmission across the nanostructure can be realized across a kink when the input and output channels are pierced by a half-integer magnetic flux quantum. Unlike for straight wires, there is an additional requirement depending on the orientation of the external magnetic field. A right-angle kink shows a unique π -periodic magnetoconductance signature as a function of the in-plane angle of the magnetic field. For a Y-junction, the transmission can be perfectly steered to either of the two possible output legs by a proper alignment of the external magnetic field. These magnetotransport signatures offer new ways to explore topological surface states and could be relevant for quantum transport experiments on nanostructures which can be realized with existing fabrication methods. [less ▲]

Charge and energy fractionalization mechanism in one-dimensional channels

in Physical Review B (2017), 96

We study the problem of injecting single electrons into interacting one-dimensional quantum systems, a fundamental building block for electron quantum optics. It is well known that such injection leads to ... [more ▼]

We study the problem of injecting single electrons into interacting one-dimensional quantum systems, a fundamental building block for electron quantum optics. It is well known that such injection leads to charge and energy fractionalization. We elucidate this concept by calculating the nonequilibrium electron distribution function in the momentum and energy domains after the injection of an energy-resolved electron. Our results shed light on how fractionalization occurs via the creation of particle-hole pairs by the injected electron. In particular, we focus on systems with a pair of counterpropagating channels, and we fully analyze the properties of each chiral fractional excitation which is created by the injection. We suggest possible routes to access their energy and momentum distribution functions in topological quantum Hall or quantum spin-Hall edge states. [less ▲]

Charge pumping through a polaron quantum dot

Poster (2017, July)

Nanoelectromechanical systems exhibit a rich phenomenology due to the interaction of electronic and mechanical degrees of freedom. If this interaction is sufficiently strong, it leads to drastic ... [more ▼]

Nanoelectromechanical systems exhibit a rich phenomenology due to the interaction of electronic and mechanical degrees of freedom. If this interaction is sufficiently strong, it leads to drastic suppression of conductance ("Franck-Condon blockade''). We show that this blockade can be exponentially lifted by application of an AC voltage. Multi-parameter drive protocols generate a pump current which enjoys the same enhancement. [less ▲]

Charge and energy fractionalization mechanism in one-dimenional chanels

in Physical Review. B : Condensed Matter (2017)