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Univ. Paris-Saclay

Sujet de stage / Master 2 Internship

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Quantum magnetotransport in shaped topological insulator nanowires

Contact: GORINI Cosimo, , cosimo.gorini@cea.fr, +33 1 69 08 72 36
How is quantum transport of Dirac electrons on the surface of a topological insulator modified by the direct coupling with the nanoscopic curvature of the samples (also called "effective gravitational fields" effect).
Possibility of continuation in PhD: Oui
Deadline for application:28/03/2023

Full description:
Mesoscopic physics is the realm of micron-size objects composed of trillions of constituents, yet behaving as single quantum entities. An example thereof are 3D topological insulator nanowires, whose insulating bulk is enclosed by highly conducting Dirac-like surface states. At low temperatures electrons cross the wires as quantum waves of (pseudo)relativistic nature. Their magnetotransport properties are thus ruled by intereference. The latter is determined/modulated by external magnetic fields and by the Berry curvature of the system, as demonstrated in a recent collaboration with experimentalists [Ziegler et al., Phys. Rev. B 97, 035157 (2018)].

Soon afterwards we also showed that the geometrical shape of a nanowire can have dramatic consequences on its magnetotransport properties [Kozlovsky et al. Phys. Rev. Lett. 124, 126804 (2020); Graf et al., Phys. Rev. B 102, 165105 (2020)]. Crucially, in shaped nanowires Dirac-like electrons propagate in curved space and may thus feel effective gravitational effects. Such emerging gravity takes place on scales which are comparable to the characteristic quantum scales of the system, much as in black holes – nanowires can however be built in labs with current technology, black holes not quite.

Among the numerous open questions in this rapidly growing field, two are most relevant for this master internship: (i) How are surface states modified in curved space? (ii) Can a quantum transport signature of effective gravitational nature be singled out in a realistic setup? To answer these both analytical and numerical methods (tight-binding simulations) will be employed.
Technics/methods used during the internship:
Schroedinger/Dirac eqs. in curved space, Landauer-Buettiker formalism, tight-binding numerical simulations

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