4 research outputs found
Unconventional quantum oscillations and evidence of non-trivial electronic states in quasi-two-dimensional electron system at complex oxide interfaces
The simultaneous occurrence of electric-field controlled superconductivity
and spin-orbit interaction makes two-dimensional electron systems (2DES)
constructed from perovskite transition metal oxides promising candidates for
the next generation of spintronics and quantum computing. It is, however,
essential to understand the electronic bands thoroughly and verify the
predicted electronic states experimentally in these 2DES to advance
technological applications. Here, we present novel insights into the electronic
states of the 2DES at oxide interfaces through comprehensive investigations of
Shubnikov-de Haas oscillations in two different systems: EuO/KTaO (EuO/KTO)
and LaAlO/SrTiO (LAO/STO). To accurately resolve these oscillations, we
conducted transport measurements in high magnetic fields up to 60 T and low
temperatures down to 100 mK. For 2D confined electrons at both interfaces, we
observed a progressive increase of oscillations frequency and cyclotron mass
with the magnetic field. We interpret these intriguing findings by considering
the existence of non-trivial electronic bands, for which the dispersion
incorporates both linear and parabolic dispersion relations. In addition to
providing experimental evidence for topological-like electronic states in
KTO-2DES and STO-2DES, the unconventional oscillations presented in this study
establish a new paradigm for quantum oscillations in 2DES based on perovskite
transition metal oxides, where the oscillations frequency exhibits quadratic
dependence on the magnetic field
Lifshitz transition enabling superconducting dome around the quantum critical point in TiSe
Superconductivity often emerges as a dome around a quantum critical point
(QCP) where long-range order is suppressed to zero temperature. So far, this
has been mostly studied in magnetically ordered materials. By contrast, the
interplay between charge order and superconductivity at a QCP is not fully
understood. Here, we present resistance measurements proving that a dome of
superconductivity surrounds the charge-density-wave (CDW) QCP in pristine
samples of 1-TiSe tuned with hydrostatic pressure. Furthermore, we use
quantum oscillation measurements to show that the superconductivity sets in at
a Lifshitz transition in the electronic band structure. We use density
functional theory to identify the Fermi pockets enabling superconductivity:
large electron and hole pockets connected by the CDW wave vector
which emerge upon partial suppression of the zero-pressure CDW gap. Hence, we
conclude that superconductivity is of interband type enabled by the presence of
hole and electron bands connected by the CDW vector. Earlier
calculations show that interband interactions are repulsive, which suggests
that unconventional s superconductivity is realised in TiSe -
similar to the iron pnictides. These results highlight the importance of
Lifshitz transitions in realising unconventional superconductivity and help
understand its interaction with CDW order in numerous materials.Comment: 21 pages, 5 figure
Electronic subbands in the a-LaAlO3/KTaO3 interface revealed by quantum oscillations in high magnetic fields
10.1103/physrevresearch.3.033234Physical Review Research333323