Abstract In a 2D electron system (2DES) the breaking of the inversion, time‐reversal and bulk crystal‐field symmetries is interlaced with the effects of spin‐orbit coupling (SOC) triggering exotic quantum phenomena. Here, epitaxial engineering is used to design and realize a 2DES characterized simultaneously by ferromagnetic order, large Rashba SOC and hexagonal band warping at the (111) interfaces between LaAlO 3 , EuTiO 3 , and SrTiO 3 insulators. The 2DES displays anomalous quantum corrections to the magneto‐conductance driven by the time‐reversal‐symmetry breaking occurring below the magnetic transition temperature. The results are explained by the emergence of a non‐trivial Berry phase and competing weak anti‐localization/weak localization back‐scattering of Dirac‐like fermions, mimicking the phenomenology of gapped topological insulators. These findings open perspectives for the engineering of novel spin‐polarized functional 2DES holding promises in spin‐orbitronics and topological electronics.

COMPTERA vise le développement de composants avancés pour les futurs systèmesd’imagerie multispectrale en gamme THz (0,3-30 THz) qui feront appel à des technologiestrès variées à la frontière de l’électronique et de l’optoélectronique, en particulier desdétecteurs à haute sensibilité adaptés à chaque gamme de longueurs d’onde (notammentmicro-bolomètres, détecteurs à effet de champ, photodétecteurs unipolaires à multi-puitsquantiques). Une partie de ces capteurs ultra-sensibles sera ensuite intégrée à dessystèmes d’imagerie adaptés à la démonstration de leurs performances.

Amplified interband emission within the 14–24 μm range is investigated in HgCdTe-based quantum wells under optical pumping. Carrier lifetimes are shown to be marginally limited only by Shockley–Read–Hall recombination, fully realizing the advantage of relativistic energy spectra of 2D HgCdTe in terms of suppressing the Auger processes. By carefully optimizing the waveguides and mitigating carrier heating, we achieve amplification thresholds as low as 1.5–2 W/cm2 at a pulse duration of 20–500 μs. With last generation quantum cascade lasers used for optical pumping, we estimate that continuous-wave HgCdTe lasers can operate in the very long-wavelength range (15–30 μm) and beyond.

Spectral studies of the photoconductivity in the temperature range of T = 5–70 K, as well as studies of the magneto-absorption and magnetotransport at T = 4.2 K, have been performed in a HgTe/CdHgTe heterostructure with a double quantum well under an “optical gate” effect. Studies of magneto-absorption spectra under the controlled optical exposure have made it possible to observe absorption lines caused by both the cyclotron resonances of electrons and holes simultaneously. The coexistence of electrons and holes in the HgTe/CdHgTe double quantum well with a relatively large bandgap (~80 meV) indicates the appearance of a strongly inhomogeneous light-induced distribution of charge carriers in the plane of the structure. Experimental results obtained clearly demonstrate disadvantages of the control of the Fermi level positions in heterostructures with HgTe/CdHgTe quantum wells by means of the optical gate.

We report on the coexistence of both normal and topological insulating phases in InAs/GaSb bilayer quantum well induced by the built-in electric field tuned optically and electrically. The emergence of topological and normal insulating phases is assessed based on the evolution of the charge carrier densities, the resistivity dependence of the gap via in-plane magnetic fields and the thermal activation of carriers. For the Hall bar device tuned optically, we observe the fingerprints associated with the presence of only the topological insulating phase. For another Hall bar processed identically but with an additional top gate, the coexistence of normal and topological insulating phases is found by electrical tuning. Our finding paves the way for utilizing a new electro-optical tuning scheme to manipulate InAs/GaSb bilayer quantum wells to obtain trivial-topological insulating interfaces in the bulk rather than at the physical edge of the device.