5 research outputs found
Nature of the current-induced insulator-to-metal transition in CaRuO as revealed by transport-ARPES
The Mott insulator CaRuO exhibits a rare insulator-to-metal
transition (IMT) induced by DC current. While structural changes associated
with this transition have been tracked by neutron diffraction, Raman
scattering, and x-ray spectroscopy, work on elucidating the response of the
electronic degrees of freedom is still in progress. Here we unveil the
current-induced modifications of the electronic states of CaRuO by
employing angle-resolved photoemission spectroscopy (ARPES) in conjunction with
four-probe transport. Two main effects emerge: a clear reduction of the Mott
gap and a modification in the dispersion of the Ru-bands. The changes in
dispersion occur exclusively along the high-symmetry direction, parallel
to the -axis where the greatest in-plane lattice change occurs. These
experimental observations are reflected in dynamical mean-field theory (DMFT)
calculations simulated exclusively from the current-induced lattice constants,
indicating a current driven structural transition as the primary mechanism of
the IMT. Furthermore, we demonstrate this phase is distinct from the
high-temperature zero-current metallic phase. Our results provide insight into
the elusive nature of the current-induced IMT of CaRuO and advance the
challenging, yet powerful, technique of transport-ARPES.Comment: 8 pages, 4 figure
Non-collinear and asymmetric polar moments at back-gated SrTiO<inf>3</inf> interfaces
The mechanism of the gate-field-induced metal-to-insulator transition of the electrons at the interface of SrTiO3 with LaAlO3 or AlOx is of great current interest. Here, we show with infrared ellipsometry and confocal Raman spectroscopy that an important role is played by a polar lattice distortion that is non-collinear, highly asymmetric and hysteretic with respect to the gate field. The anomalous behavior and the large lateral component of the underlying local electric field is explained in terms of the interplay between the oxygen vacancies, that tend to migrate and form extended clusters at the antiferrodistortive domain boundaries, and the interfacial electrons, which get trapped/detrapped at the oxygen vacancy clusters under a positive/negative gate bias. Our findings open new perspectives for the defect engineering of lateral devices with strongly enhanced and hysteretic local electric fields that can be manipulated with various parameters, like strain, temperature, or photons.F.L. and C.B. acknowledge enlightening discussions with S. Das, J. Maier, R. Merkle, A. Dubroka, and B. I. Shklovskii. Work at the University of Fribourg was supported by the Schweizerische Nationalfonds (SNF) by Grant No. 200020-172611. M.B. acknowledges support from the ERC Advanced grant n° 833973 “FRESCO” and the QUANTERA project “QUANTOX”. G.H. acknowledges financial support from Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) through the Severo Ochoa FUNFUTURE (CEX2019-000917-S) and Grant No. PID2020-118479RB-I00, and Generalitat de Catalunya (2017 400 SGR 1377).With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe
Imaging mesoscopic antiferromagnetic spin textures in the dilute limit from single-geometry resonant coherent x-ray diffraction
The detection and manipulation of antiferromagnetic domains and topological antiferromagnetic textures are of central interest to solid-state physics. A fundamental step is identifying tools to probe the mesoscopic texture of an antiferromagnetic order parameter. In this work, we demonstrate that Bragg coherent diffractive imaging can be extended to study the mesoscopic texture of an antiferromagnetic order parameter using resonant magnetic x-ray scattering. We study the onset of the antiferromagnet transition in PrNiO3, focusing on a temperature regime in which the antiferromagnetic domains are dilute in the beam spot and the coherent diffraction pattern modulating the antiferromagnetic peak is greatly simplified. We demonstrate that it is possible to extract the arrangements and sizes of these domains from single diffraction patterns and show that the approach could be extended to a time-structured light source to study the motion of dilute domains or the motion of topological defects in an antiferromagnetic spin texture