FisMat2017 - Submission - View

Abstract's title: LaVO3-based heterostructures
Submitting author: Paolo Franceschini
Affiliation: Università Cattolica del Sacro Cuore di Brescia - Dipartimento di Matematica e Fisica “Niccolò Tartaglia”
Affiliation Address: Università Cattolica del Sacro Cuore di Brescia Sede del Buon Pastore Via Musei 41 - 25121 Brescia
Country: Italy
Oral presentation/Poster (Author's request): Poster
Other authors and affiliations: Pasquale Orgiani(CNR-SPIN, UOS Salerno, 84084 Fisciano, Italy), Giancarlo Panaccione (CNR-IOM, TASC Laboratory in Area Science Park, 34139 Trieste, Italy), Giorgio Rossi (Department of Physics, University of Milano, 20133 Milano, Italy), Francesco Banfi (Department of Physics, Università Cattolica del Sacro Cuore, Brescia I-25121, Italy), Gabriele Ferrini (Department of Physics, Università Cattolica del Sacro Cuore, Brescia I-25121, Italy), Claudio Giannetti(Department of Physics, Università Cattolica del Sacro Cuore, Brescia I-25121, Italy)
LaVO3 (LVO) is one of the most promising candidates to investigate and, possibly, exploit
quantum-coherent effects in heterostructures; indeed, it is a prototypical Mott-Hubbard insulator
(direct gap of ~ 1,1 eV) with a 3d2 electronic configuration of V3+. The fundamental optical
excitation is the transition from the lower (LHB) to the upper Hubbard band (UHB), which
corresponds to moving an electron from one V atom to its neighbouring V-site. Interestingly,
LVO exhibits large quantum orbital fluctuations at room temperature, in the sense that the
orbital occupation of the t2g is strongly fluctuating on a frequency range which is determined
by quantum effects instead of kBT. However, at 143 K, LVO single crystals undergo a magnetic
transition from paramagnetic to antiferromagnetic and also a lattice-structural phase transition
from orthorhombic to monoclinic lattice accompanied concomitantly with an orbital ordering
as temperature is lowered at 141 K. Thus, the strong incoherent orbital fluctuations are almost
completely suppressed in the monoclinic low-temperature phase, when they turn into a
phase-coherent condensate in which the orbital occupation assumes a well defined (phase stable)
pattern in space and time.
The goal of my project is to synthesize LVO heterostructures in which coherent-transport phenomena
are observed at ambient temperatures. In particular, we aim at controlling the decoherence
timescale of optical excitations by tuning the distance from the orbital-ordering phase
transition. The first step along this way is the growth of LVO thin-films by PLD and and their
characterization by RHEED and LEED. The substrate is SrTiO3 (STO), although different
substrates have been tested to address the role of the substrate-induced strain in determining
the electronic properties of LVO. The LVO charge-ordering transition at low temperature is
investigated by XPS and XAS, in order to address the minimum thickness at which the bulk
properties are maintained. This knowledge would constitute the starting point for the synthesis
of STO/LVO/STO heterostructures, which constitute the building blocks for solid-state based
quantum devices working at ambient.
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