Geometric constraints on phase coexistence in vanadium dioxide single crystals

Abstract

The appearance of stripe phases is a characteristic signature of strongly correlated quantum materials, and its origin in phase-changing materials has only recently been recognized as the result of the delicate balance between atomic and mesoscopic materials properties. A vanadium dioxide (VO) single crystal is one such strongly correlated material with stripe phases. Infrared nano-imaging on low-aspect-ratio, single-crystal VO microbeams decorated with resonant plasmonic nanoantennas reveals a novel herringbone pattern of coexisting metallic and insulating domains intercepted and altered by ferroelastic domains, unlike previous reports on high-aspect-ratio VO crystals where the coexisting metal/insulator domains appear as alternating stripe phases perpendicular to the growth axis. The metallic domains nucleate below the crystal surface and grow towards the surface with increasing temperature as suggested by the near-field plasmonic response of the gold nanorod antennas.

Nano-Resolved Current-Induced Insulator-Metal Transition in the Mott Insulator Ca2RuO4

“…This possibility is especially true for SCEMs, since the competition between many degrees of freedom including orbital, lattice, and magnetic ordering can yield the coexistence of multiple phases in the same crystal, triggered by minute perturbations of the electronic and lattice subsystems. Field-induced filament growth and temperature-induced phase percolation at microscopic scales are extensively reported in 3d transition-metal oxides, including vanadates, manganites, and cuprates [10][11][12][13][14][15][16][17]. Therefore, direct insight into the spatial structure and thermal aspects of quantum phase transitions is urgently needed.…”

Reconfigurable infrared hyperbolic metasurfaces using phase change materials

“…Existing metasurfaces frequently utilize metallic polaritonic 4 elements with high absorption losses 5 , and/or fixed geometrical designs that serve a single function. Here we overcome these limitations by demonstrating a reconfigurable hyperbolic 6 metasurface comprising of a heterostructure of isotopically enriched hexagonal boron nitride (hBN) [7][8][9][10] in direct contact with the phase-change material (PCM) vanadium dioxide (VO2) [11][12][13][14] . Spatially localized metallic and dielectric domains in VO2 change the wavelength of the hyperbolic phonon polaritons (HPhPs) supported in hBN by a factor 1.6 at 1450cm -1 .…”

“…Propagation of HPhPs is strongly influenced by the local dielectric environment 21,23 , so we investigated the influence of the VO2 phase transition by measuring the s-SNOM response of the sample as a function of temperature, traversing the full dielectric-to-metal transition between 60-80°C 14 . Individual VO2 domains are directly observable with s-SNOM due to the dielectric contrast between domains, with metallic (dielectric) VO2 appearing as bright (dark) regions (Fig 1c) [11][12][13][14] . As the device is heated further (Fig.…”

The Dynamic Mixed Metal–Insulator Phase in Self‐Heated Needle‐Like VO2 Single Crystals

“…Changes in the microstructure and damage associated with the structural transition may accompany very significant changes in the resistivity and in the optical properties; much of today's development efforts in this field are devoted to finding strategies that enable highly repetitive cycling through the phase transition in thin films without structural damage . In single crystals and crystallites, the mixed phase reached by heating as well as self‐heating under near‐equilibrium conditions contains a variety of static domain patterns such as triangular domains, stripes, or herring bones . Dynamic domain patterns appear in single crystals in the current‐controlled negative differential resistivity (CC‐NDR) regime of the nonlinear I – V characteristic governed by self‐heating.…”

“…[14] In single crystals and crystallites, the mixed phase reached by heating as well as self-heating under near-equilibrium conditions contains a variety of static domain patterns such as triangular domains, [15,16] stripes, [15,17] or herring bones. [17] Dynamic domain patterns appear in single crystals in the current-controlled negative differential resistivity (CC-NDR) regime [18] of the nonlinear I-V characteristic governed by self-heating. In their simplest form, they consist of narrow insulating domains sliding along a free-standing needle-like crystal within a metallic domain, in the sense of the electric current.…”