Quasistatic antiferromagnetism in the quantum wells of SmTiO3/SrTiO3 heterostructures

Abstract

High carrier density quantum wells embedded within a Mott insulating matrix present a rich arena for exploring unconventional electronic phase behavior ranging from non-Fermi-liquid transport and signatures of quantum criticality to pseudogap formation. Probing the proposed connection between unconventional magnetotransport and incipient electronic order within these quantum wells has however remained an enduring challenge due to the ultra-thin layer thicknesses required. Here we address this challenge by exploring the magnetic properties of high-density SrTiO 3 quantum wells embedded within the antiferromagnetic Mott insulator SmTiO 3 via muon spin relaxation and polarized neutron reflectometry measurements. The one electron per planar unit cell acquired by the nominal d 0 band insulator SrTiO 3 when embedded within a d 1 Mott SmTiO 3 matrix exhibits slow magnetic fluctuations that begin to freeze into a quasistatic spin state below a critical temperature T *. The appearance of this quasistatic well magnetism coincides with the previously reported opening of a pseudogap in the tunneling spectra of high carrier density wells inside this film architecture. Our data suggest a common origin of the pseudogap phase behavior in this quantum critical oxide heterostructure with those observed in bulk Mott materials close to an antiferromagnetic instability.

Controlling a Van Hove singularity and Fermi surface topology at a complex oxide heterostructure interface

“…Transport measurements have shown two different regimes as a function of thickness. Specifically, the temperature dependence of resistivity shows a sharp change from a behavior to a (with ) behavior as the number of layers decreases, with a sharp crossover at the critical thickness 5-SrO where a divergence of resistivity and other electronic properties, such as the Hall coefficient, is observed 15–18 . While the origin of these exotic properties is believed to be related to quantum confinement, involving atomic orbital and coupling/correlation of the interfacial electron liquids, no study of the electronic structures at these buried interfaces exists.…”

“…Their properties can be controlled by varying the parent constituents and/or their stacking geometry 5,9–14 . One notable example is the emergence of electron liquid behavior, created by novel charge mismatch in the quantum well of nonpolar band insulator SrTiO 3 embedded in polar Mott insulator, such as SmTiO 3 , showing hallmarks of strongly correlated phases, including non-Fermi liquid behavior 15,16 , transport lifetime separation 16 , pseudo-gap 17 , spin density waves 15 , and antiferromagnetism 18 . These behaviors are tuned by the thickness of the quantum wells in SrTiO 3 , defined by the number of SrO layers (-SrO), embedded in SmTiO 3 .…”

Coupling of magnetic phases at nickelate interfaces

“…Here, the LEM instrument produces low energy muons with tunable energies in the range of 1 to 30 keV. This allows access to different implantation depths in solids and thin films, ranging from a fraction of a nm to several hundred nm [42][43][44][45]. For our superlattices, simulated muon implantation profiles were calculated for various implantation energies with the TRIM.SP Monte Carlo code [46,47].…”

Effect of capping layers on the near-surface region of SrVO3 films

“…Advancement in thin film synthesis techniques has heralded prospects of emergent interface physics 1 and of maturing some of these phenomena toward practical devices. 2,3 Moreover, driving thin films into the ultrathin (few nanometers) regime can give rise to interesting electronic and magnetic phenomena, driven by quantum confinement [4][5][6][7][8] and dimensional crossover. [9][10][11][12] From a device point of view, the application of an electric field is a desirable strategy for controlling and switching material properties, such as metal-insulator transitions.…”