Large Tunability of Strain in WO₃ Single-Crystal Microresonators Controlled by Exposure to H₂ Gas

Strain engineering is one of the most effective approaches to manipulate the physical state of materials, control their electronic properties, and enable crucial functionalities. Because of their rich phase diagrams arising from competing ground states, quantum materials are an ideal playground for on-demand material control and can be used...

Light control of the nanoscale phase separation in heteroepitaxial nickelates

Strongly correlated materials show unique solid-state phase transitions with rich nanoscale phenomenology that can be controlled by external stimuli. Particularly interesting is the case of light–matter interaction in the proximity of the metal–insulator transition of heteroepitaxial nickelates. In this work, we use near-infrared laser light in...

Single-crystal Pt-decorated WO₃ ultrathin films: a platform for sub-ppm hydrogen sensing at room temperature

Hydrogen-related technologies are rapidly developing, driven by the necessity of efficient and high-density energy storage. This poses new challenges to the detection of dangerous gases, in particular the realization of cheap, sensitive, and fast hydrogen sensors. Several materials are being studied for this application, but most present...

Balanced electron-hole transport in spin-orbit semimetal SrIrO 3 heterostructures

Relating the band structure of correlated semimetals to their transport properties is a complex and often open issue. The partial occupation of numerous electron and hole bands can result in properties that are seemingly in contrast with one another, complicating the extraction of the transport coefficients of different bands. The 5d oxide...

Spin-Orbit Semimetal SrIrO3 in the Two-Dimensional Limit

We investigate the thickness-dependent electronic properties of ultrathin SrIrO3 and discover a transition from a semimetallic to a correlated insulating state below 4 unit cells. Low-temperature magnetoconductance measurements show that spin fluctuations in the semimetallic state are significantly enhanced while approaching the transition...

Metal–Insulator Transitions in Heterostructures of Quantum Materials

This thesis is an experimental investigation of the physical properties of different transition metal oxide ultra-thin films. A common feature of these various materials and structures is that they exhibit a solid-state phase transition from a metallic to an insulating state, which is triggered upon changing sample composition, or by varying an...

Insulator-to-Metal Transition at Oxide Interfaces Induced by WO₃ Overlayers

Interfaces between complex oxides constitute a unique playground for two-dimensional electron systems (2DESs), where superconductivity and magnetism can arise from combinations of bulk insulators. The 2DES at the LaAlO₃/SrTiO₃ interface is one of the most studied in this regard, and its origin is determined by the polar...

Multiple Supersonic Phase Fronts Launched at a Complex-Oxide Heterointerface

Selective optical excitation of a substrate lattice can drive phase changes across heterointerfaces. This phenomenon is a nonequilibrium analogue of static strain control in heterostructures and may lead to new applications in optically controlled phase change devices. Here, we make use of time-resolved nonresonant and resonant x-ray...

Striped nanoscale phase separation at the metal-insulator transition of heteroepitaxial nickelates

Nucleation processes of mixed-phase states are an intrinsic characteristic of first-order phase transitions, typically related to local symmetry breaking. Direct observation of emerging mixed-phase regions in materials showing a first-order metal-insulator transition (MIT) offers unique opportunities to uncover their driving mechanism. Using...

Epitaxial growth and thermodynamic stability of SrIrO₃/SrTiO₃ heterostructures

Obtaining high-quality thin films of 5d transition metal oxides is essential to explore the exotic semimetallic and topological phases predicted to arise from the combination of strong electron correlations and spin-orbit coupling. Here, we show that the transport properties of SrIrO₃ thin films, grown by pulsed laser deposition,...

Giant negative magnetoresistance driven by spin-orbit coupling at the LaAlO3/SrTiO3 interface

The LaAlO3=SrTiO3 interface hosts a two-dimensional electron system that is unusually sensitive to the application of an in-plane magnetic field. Low-temperature experiments have revealed a giant negative magnetoresistance (dropping by 70%), attributed to a magnetic-field induced transition between interacting phases of conduction electrons with...