Nanoscale self-organization and metastable non-thermal metallicity in Mott insulators

Abstract

Mott transitions in real materials are first order and almost always associated with lattice distortions, both features promoting the emergence of nanotextured phases. This nanoscale self-organization creates spatially inhomogeneous regions, which can host and protect transient non-thermal electronic and lattice states triggered by light excitation. Here, we combine time-resolved X-ray microscopy with a Landau-Ginzburg functional approach for calculating the strain and electronic real-space configurations. We investigate V2O3, the archetypal Mott insulator in which nanoscale self-organization already exists in the low-temperature monoclinic phase and strongly affects the transition towards the high-temperature corundum metallic phase. Our joint experimental-theoretical approach uncovers a remarkable out-of-equilibrium phenomenon: the photo-induced stabilisation of the long sought monoclinic metal phase, which is absent at equilibrium and in homogeneous materials, but emerges as a metastable state solely when light excitation is combined with the underlying nanotexture of the monoclinic lattice.

Metal–Insulator Transition of Single-Crystal V2O3 through van der Waals Interface Engineering

“…However, its epitaxial thin film shows a continuous transition due to the existence of massive heterogeneous nucleation sites and crystallographic defects. ,,− V 2 O 3 nanowires, fabricated by plasma etching on epitaxial thin films, exhibit multiple-stage resistance changes during the metal–insulator transition, , reflecting the number of nucleation sites in the small nanowire. Recently, nanoresolved infrared microscopy and X-ray photoemission electron microscopy , have revealed the real-space evolution of a striped multiple-domain pattern in thin films during the phase transition. The multiple-domain pining phenomenon in these thin films , is likely due to defects which lead to low nucleation barrier possibly because of a strong film–substrate interaction.…”

“…Recently, nanoresolved infrared microscopy and X-ray photoemission electron microscopy , have revealed the real-space evolution of a striped multiple-domain pattern in thin films during the phase transition. The multiple-domain pining phenomenon in these thin films , is likely due to defects which lead to low nucleation barrier possibly because of a strong film–substrate interaction. Scanning photoelectron microscopy has revealed the formation of a trigonal-shaped domain in Cr-doped V 2 O 3 .…”

“…31,32,44−46 V 2 O 3 nanowires, fabricated by plasma etching on epitaxial thin films, exhibit multiple-stage resistance changes during the metal−insulator transition, 47,48 reflecting the number of nucleation sites in the small nanowire. Recently, nanoresolved infrared microscopy 31 and X-ray photoemission electron microscopy 44,45 have revealed the real-space evolution of a striped multiple-domain pattern in thin films during the phase transition. The multiple-domain pining phenomenon in these thin films 44,45 is likely due to defects which lead to low nucleation barrier possibly because of a strong film−substrate interaction.…”

Pattern Formation by Electric-Field Quench in a Mott Crystal

“…13−16 Depending on its amplitude, an applied gate voltage can yield a dielectric breakdown and electronic avalanches 17 or activate collective low-energy lattice and spin−orbital excitations. 18 The transitions which emerge from the Mott insulating state can hence involve multiple degrees of freedom and be marked or not by significant changes in the crystal structure, as is the case for V 2 O 3 , 19 VO 2 , 20−23 and Fe 3 O 4 systems. 24 In this framework, Ca 2 RuO 4 (CRO) represents a paradigmatic material platform to assess the interplay of electron correlations and electron− lattice coupling in the presence of multiorbital physics 25−27 with spin−orbit and Hund interactions.…”

“…There are two scenarios that are often encountered in proximity of Mott phases: (i) the occurrence of superconductivity when the insulating phase is destroyed, as for the emblematic case of cuprates with magnetism playing an important role too, and (ii) the tendency to form inhomogeneous electronic patterns due to the first order character of the Mott transition and the competing length scales of localized and itinerant electronic degrees of freedom. − Recently, it has been pointed out that the application of an electric field, both static or dynamic, can be an ideal knob to control the conducting properties of correlated materials by inducing insulator-to-metal transitions and novel quantum phases of matter. − Depending on its amplitude, an applied gate voltage can yield a dielectric breakdown and electronic avalanches or activate collective low-energy lattice and spin–orbital excitations . The transitions which emerge from the Mott insulating state can hence involve multiple degrees of freedom and be marked or not by significant changes in the crystal structure, as is the case for V 2 O 3 , VO 2 , − and Fe 3 O 4 systems . In this framework, Ca 2 RuO 4 (CRO) represents a paradigmatic material platform to assess the interplay of electron correlations and electron–lattice coupling in the presence of multiorbital physics − with spin–orbit and Hund interactions .…”