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The two-dimensional electron system formed at the interface between the insulating oxides LaAlO3 and SrTiO3 exhibits ferromagnetism, superconductivity, and a wide range of unique magnetotransport properties. A key challenge is to find a unified microscopic mechanism that underlies these emergent phenomena. Here we show that a universal Lifshitz transition between d-orbitals lies at the core of the observed transport phenomena in this system. Our measurements find a critical electronic density at which the transport switches from single to multiple carriers. This density has a universal value, independent of the LaAlO3 thickness and electron mobility. The characteristics of the transition, its universality, and its compatibility with spectroscopic measurements establish it as a transition between d-orbitals of different symmetries. A simple band model, allowing for spin-orbit coupling at the atomic level, connects the observed universal transition to a range of reported magnetotransport properties. Interestingly, we also find that the maximum of the superconducting transition temperature occurs at the same critical transition, indicating a possible connection between the two phenomena. Our observations demonstrate that orbital degeneracies play an important role in the fascinating behavior observed so far in these oxides.

Abstract: One of the more interesting and unusual aspects of the present-day Martian climate is the seasonal condensation of the atmosphere during polar winter. Heat cannot be transported from lower latitudes rapidly enough by the thin CO2 atmosphere to offset radiative cooling within the polar night, and the air cools to the CO2 frost point. Pressure changes recorded by the Viking landers indicate that about one third of the atmosphere is exchanged with the seasonal polar caps each year through the condensation/sublimation cycle. Does it snow? I will present recent infrared observations by the Mars Climate Sounder (on NASA's Mars Reconnaissance Orbiter), which reveal the distribution and behavior of polar CO2 clouds for the first time, elucidating the role of snowfall in forming the seasonal polar caps. A ~300-km snow cloud persists over the south polar residual cap (SPRC) for the entire winter season, making it the snowiest place on Mars.We find that CO2 snowfall contributes at least 7-15% of seasonal deposition at the SPRC, and the granularity of the snow deposits may enable their interannual preservation by enhancing their summertime albedo. Thus, the mode of deposition may be a key to buffering the Martian atmosphere against complete sublimation on interannual time scales.