title: Strong confinement-induced engineering of the g factor and lifetime of conduction electron spins in Ge quantum wells.
abstract: Control of electron spin coherence via external fields is fundamental in spintronics. Its implementation demands a host material that accommodates the desirable but contrasting requirements of spin robustness against relaxation mechanisms and sizeable coupling between spin and orbital motion of the carriers. Here, we focus on Ge, which is a prominent candidate for shuttling spin quantum bits into the mainstream Si electronics. So far, however, the intrinsic spin-dependent phenomena of free electrons in conventional Ge/Si heterojunctions have proved to be elusive because of epitaxy constraints and an unfavourable band alignment. We overcome these fundamental limitations by investigating a two-dimensional electron gas in quantum wells of pure Ge grown on Si. These epitaxial systems demonstrate exceptionally long spin lifetimes. In particular, by fine-tuning quantum confinement we demonstrate that the electron Landé g factor can be engineered in our CMOS-compatible architecture over a range previously inaccessible for Si spintronics.
authors.affiliation: LNESS and Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, via Cozzi 55, Milano 20125, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Giorgioni
authors.affiliation: Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, via Cozzi 55, Milano 20125, Italy.
authors.forename: Stefano
authors.identifier: 0000-0001-8951-4646
authors.initials: S
authors.lastname: Paleari
authors.affiliation: LNESS and Dipartimento di Fisica, Politecnico di Milano, via Anzani 42, Como 22100, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Cecchi
authors.affiliation: LNESS and Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, via Cozzi 55, Milano 20125, Italy.
authors.forename: Elisa
authors.identifier: 0000-0002-6952-2531
authors.initials: E
authors.lastname: Vitiello
authors.affiliation: LNESS and Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, via Cozzi 55, Milano 20125, Italy.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Grilli
authors.affiliation: LNESS and Dipartimento di Fisica, Politecnico di Milano, via Anzani 42, Como 22100, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Isella
authors.affiliation: Institut für Halbleiter-und Festkörperphysik, Johannes Kepler University, Altenbergerstrasse 69, Linz 4040, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Jantsch
authors.affiliation: Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, via Cozzi 55, Milano 20125, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Fanciulli
authors.affiliation: LNESS and Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, via Cozzi 55, Milano 20125, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Pezzoli