DQMP Forum - Pr2Ir2O7: Topological Phase and Correlation Physics & Band Structure and Spin-Orbital Texture of the (111)-KTaO3 Two-Dimensional Electron Gas

26.02.2019 13:00 – 14:00

Pr2Ir2O7: Topological Phase and Correlation Physics
Kai Wang (group of Prof. van der Marel)

Pyrochlore irritates have been predicted to give rise to 3D nontrivial topological properties in the past decade. A magnetic type Weyl semimetal phase probably exist in this series, preserving cubic symmetry
but time reversal symmetry breaking. More surprisingly, due to 5d Ir electron extended orbit, the energy scale of electron correlation effect and spin-orbit coupling strength become comparable, leading to a rich
novel phase that emerge. We investigate DC transport and charge dynamics of ab plane. Optical conductivity indicates a strong temperature dependence, showing a successive phase transition, including
topological Weyl semi-metal and Mott insulating phase. More importantly we observe an opening of full gap in the at low temperatures, however coherent spectral weight still demonstrates temperature square
dependence, which greatly deviated from the thermal excited behavior in gap phase. We argue that the new physics could be at play.

Band Structure and Spin-Orbital Texture of the (111)-KTaO3 Two-Dimensional Electron Gas
Flavio Bruno (group of Prof. Baumberger)

Two-dimensional electron gases (2DEGs) in oxides show great potential for discovering new physical phenomena and at the same time hold promise for electronic applications. In this work we use angle
resolved photoemission to determine the electronic structure of a 2DEG stabilized in the (111)-oriented surface of the strong spin orbit coupling material KTaO3. Our measurements reveal multiple sub-bands
that emerge as a consequence of quantum confinement and form a six-fold symmetric Fermi surface. This electronic structure is well reproduced by self-consistent tight-binding supercell calculations. Based on
these calculations we determine the spin and orbital texture of the 2DEG. We show that the 2DEG Fermi surface is derived from bulk J = 3/2 states and exhibits an unconventional anisotropic Rashba-like lifting
of the spin-degeneracy. Spin-momentum locking holds only for high symmetry directions and a strong out-of-plane spin component renders the spin-texture three-fold symmetric. We find that the average spinsplitting
on the Fermi surface is an order of magnitude larger than in SrTiO3, which should translate into an enhancement in the spin-orbitronic response of (111)-KTaO3 2DEG based devices.

Forum Committee: C. Lichtensteiger, N. Ubrig, A. Tamai (18.2.2019)

Lieu

Bâtiment: Ecole de Physique

Auditoire Stückelberg

Organisé par

Département de physique de la matière quantique

Intervenant-e-s

Kai Wang, Assistant Doctorant, UNIGE, Groupe Prof. van der Marel
Flavio Bruno, Collaborateur Scientifique, UNIGE, Groupe Prof. Baumberger

entrée libre

Classement

Catégorie: Forum

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