| 1. |
- Curcio, Davide, et al.
(författare)
-
Current-driven insulator-to-metal transition without Mott breakdown in Ca2RuO4
- 2023
-
Ingår i: Physical Review B. - 2469-9950. ; 108:16
-
Tidskriftsartikel (refereegranskat)abstract
- The electrical control of a material's conductivity is at the heart of modern electronics. Conventionally, this control is achieved by tuning the density of mobile charge carriers. A completely different approach is possible in Mott insulators such as Ca2RuO4, where an insulator-to-metal transition (IMT) can be induced by a weak electric field or current. While the driving force of the IMT is poorly understood, it has been thought to be a breakdown of the Mott state. Using in operando angle-resolved photoemission spectroscopy, we show that this is not the case: The current-induced conductivity is caused by the formation of in-gap states with only a minor reorganization of the Mott state. Electronic structure calculations show that these in-gap states form at the boundaries of structural domains that emerge during the IMT. At such boundaries, the overall gap is drastically reduced, even if the structural difference between the domains is small and the individual domains retain their Mott character. The inhomogeneity of the sample is thus key to understanding the IMT, as it leads to a nonequilibrium semimetallic state that forms at the interface of Mott domains.
|
|
| 2. |
- Fortier, A., et al.
(författare)
-
CHEOPS in-flight performance: A comprehensive look at the first 3.5 yr of operations
- 2024
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 687
-
Tidskriftsartikel (refereegranskat)abstract
- Context. Since the discovery of the first exoplanet almost three decades ago, the number of known exoplanets has increased dramatically. By beginning of the 2000s it was clear that dedicated facilities to advance our studies in this field were needed. The CHaracterising ExOPlanet Satellite (CHEOPS) is a space telescope specifically designed to monitor transiting exoplanets orbiting bright stars. In September 2023, CHEOPS completed its nominal mission duration of 3.5 yr and remains in excellent operational conditions. As a testament to this, the mission has been extended until the end of 2026. Aims. Scientific and instrumental data have been collected throughout in-orbit commissioning and nominal operations, enabling a comprehensive analysis of the missiona's performance. In this article, we present the results of this analysis with a twofold goal. First, we aim to inform the scientific community about the present status of the mission and what can be expected as the instrument ages. Secondly, we intend for this publication to serve as a legacy document for future missions, providing insights and lessons learned from the successful operation of CHEOPS. Methods. To evaluate the instrument performance in flight, we developed a comprehensive monitoring and characterisation (M&C) programme. It consists of dedicated observations that allow us to characterise the instrumenta's response and continuously monitor its behaviour. In addition to the standard collection of nominal science and housekeeping data, these observations provide valuable input for detecting, modelling, and correcting instrument systematics, discovering and addressing anomalies, and comparing the instrumenta's actual performance with expectations. Results. The precision of the CHEOPS measurements has enabled the mission objectives to be met and exceeded. The satellitea's performance remains stable and reliable, ensuring accurate data collection throughout its operational life. Careful modelling of the instrumental systematics allows the data quality to be significantly improved during the light curve analysis phase, resulting in more precise scientific measurements. Conclusions. CHEOPS is compliant with the driving scientific requirements of the mission. Although visible, the ageing of the instrument has not affected the missiona's performance. The satellitea's capabilities remain robust, and we are confident that we will continue to acquire high-quality data during the mission extension.
|
|
| 3. |
- Horio, M., et al.
(författare)
-
Orbital-selective metal skin induced by alkali-metal-dosing Mott-insulating Ca 2 RuO 4
- 2023
-
Ingår i: Communications Physics. - 2399-3650. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Doped Mott insulators are the starting point for interesting physics such as high temperature superconductivity and quantum spin liquids. For multi-band Mott insulators, orbital selective ground states have been envisioned. However, orbital selective metals and Mott insulators have been difficult to realize experimentally. Here we demonstrate by photoemission spectroscopy how Ca2RuO4, upon alkali-metal surface doping, develops a single-band metal skin. Our dynamical mean field theory calculations reveal that homogeneous electron doping of Ca2RuO4 results in a multi-band metal. All together, our results provide evidence for an orbital-selective Mott insulator breakdown, which is unachievable via simple electron doping. Supported by a cluster model and cluster perturbation theory calculations, we demonstrate a type of skin metal-insulator transition induced by surface dopants that orbital-selectively hybridize with the bulk Mott state and in turn produce coherent in-gap states.
|
|
| 4. |
- Marques, Carolina A., et al.
(författare)
-
Spin-orbit coupling induced Van Hove singularity in proximity to a Lifshitz transition in Sr4Ru3O10
- 2024
-
Ingår i: npj Quantum Materials. - 2397-4648. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- Van Hove singularities (VHss) in the vicinity of the Fermi energy often play a dramatic role in the physics of strongly correlated electron materials. The divergence of the density of states generated by VHss can trigger the emergence of phases such as superconductivity, ferromagnetism, metamagnetism, and density wave orders. A detailed understanding of the electronic structure of these VHss is therefore essential for an accurate description of such instabilities. Here, we study the low-energy electronic structure of the trilayer strontium ruthenate Sr4Ru3O10, identifying a rich hierarchy of VHss using angle-resolved photoemission spectroscopy and millikelvin scanning tunneling microscopy. Comparison of k-resolved electron spectroscopy and quasiparticle interference allows us to determine the structure of the VHss and demonstrate the crucial role of spin-orbit coupling in shaping them. We use this to develop a minimal model from which we identify a mechanism for driving a field-induced Lifshitz transition in ferromagnetic metals.
|
|
