Conventional Phase Diagram Research Articles

Axial, planar-diagonal, body-diagonal fields on the cubic-spin spin glass in d=3: A plethora of ordered phases under finite fields.

A nematic phase, previously seen in the d=3 classical Heisenberg spin-glass system, occurs in the n-component cubic-spin spin-glass system, between the low-temperature spin-glass phase and the high-temperature disordered phase, for number of spin components n≥3, in spatial dimension d=3, thus constituting a liquid-crystal phase in a dirty (quenched-disordered) magnet. Furthermore, under application of a variety of uniform magnetic fields, a veritable plethora of phases is found. Under uniform magnetic fields, 17 different phases and two spin-glass phase diagram topologies (meaning the occurrences and relative positions of the many phases), qualitatively different from the conventional spin-glass phase diagram topology, are seen. The chaotic rescaling behaviors and their Lyapunov exponents are calculated in each of these spin-glass phase diagram topologies. These results are obtained from renormalization-group calculations that are exact on the d=3 hierarchical lattice and, equivalently, approximate on the cubic spatial lattice. Axial, planar-diagonal, or body-diagonal finite-strength uniform fields are applied to n=2 and 3 component cubic-spin spin-glass systems in d=3.

Metastable network phases from controlled self-assembly of high- χ block copolymers

Well-ordered nanonetwork materials with triply periodic minimal surface texture are appealing and promising for innovative properties such as optical and mechanical metamaterials as inspired by nature (e.g., the photonic property from the wing structure of a butterfly and the high-impact property from the dactyl club of a mantis shrimp). Network structures possess self-supporting frameworks, open-cell character, high porosity, and large specific surface area, giving specific functions and complexity for practical applications. Here, a facile approach with simple routes for acquiring of metastable network phases beyond conventional phase diagrams is proposed and examined. By taking advantage of controlled self-assembly for high-interaction-parameter () block copolymers (BCPs), it is feasible to acquire network phases from the use of a selective solvent for self-assembly under controlled evaporation of the solvent. In contrast with the thermodynamically stable equilibrium phases from intrinsic BCPs and their blends with conventional network phases, a variety of kinetically trapped network phases with a high degree of ordering can be obtained from a single-composition lamellar phase, giving an easy method to acquire metastable network phases even for a primitive phase with large packing frustration (i.e., entropic penalty). Furthermore, the windows for network phases can even be expanded through controlled self-assembly of star-BCPs as compared with the linear-conformation diblocks. As a result, the topological architecture of BCPs could be another controlling factor to vary the phase behaviors, which may provide easy access to a variety of metastable network phases from thermodynamically stable phases through a kinetically controlled process for self-assembly. Published by the American Physical Society 2024

The Influence of Wettability Effect and Adsorption Thickness on Nanoconfined Methane Phase Behavior: Vapor-Liquid Co-Existence Curves and Phase Diagrams

Research interest in the behavior of methane inside nanopores has been growing, driven by the substantial geological reserves of shale gas and coalbed methane. The phase diagram of methane in nanopores differs significantly from its bulk state, influencing its existing form and pertinent physical properties—such as density and viscosity—at specific pressures and temperatures. Currently, there is a lack of effort to understand the nanoconfinement effect on the methane phase diagram; this is a crucial issue that needs urgent attention before delving into other aspects of nanoconfined methane behavior. In this study, we establish a fully coupled model to predict the methane phase diagram across various scales. The model is based on vapor-liquid fugacity equilibrium, considering the shift in critical pressure and temperature induced by pore size shrinkage and adsorption-phase thickness. Notably, our proposed model incorporates the often-overlooked factor of capillary pressure, which is greatly amplified by nanoscale pore size and the presence of the adsorption phase. Additionally, we investigated the impact of surface wettability, correlated to capillary pressure and the shift in critical properties, on the methane phase diagram. Our results indicate that (a) as pore size decreases, the methane phase diagram becomes more vertical, suggesting a transition from a gaseous to a liquid state for some methane molecules, which is contrary to the conventional phase diagram; (b) enhancing surface wettability results in a more vertical phase diagram, with the minimum temperature corresponding to 0 MPa pressure on the phase diagram, increasing by as much as 87.3%; (c) the influence of capillary pressure on the phase diagram is more pronounced under strong wettability conditions compared to weak wettability, and the impact from the shift in critical properties can be neglected when the pore size exceeds 50 nm.

Effects of temperature and shear conditions on lamellar-to-onion transition in nonionic surfactant/water systems

The effects of temperature and shear conditions on the lamellar-to-multilamellar vesicle (MLV) phase transition were elucidated using rheometry (Rheo)–small-angle light scattering (SALS) measurements for a system comprising C12E4.2 (a nonionic surfactant containing distributed ethylene oxide; 40 wt%) and water (60 wt%). Small-angle X-ray scattering (SAXS) measurements indicated that the bilayer d-spacing widened up to 30 °C, and further increasing the temperature caused the bilayer to fluctuate more easily. Rheo–SALS measurements indicated that the C12E4.2 viscosity increased, and a cloverleaf pattern appeared, as previously reported for other CnEm systems, indicating a phase transition. The decrease in vesicle size with increasing shear rate was slower than that reported for the non-distributed system. In a conventional dynamic phase diagram prepared in the shear-rate–temperature space, regions appeared in which temperatures and shear rates required for the phase transition were inconsistent. When a shear-stress-controlled flow was applied, the shear stress magnitude required for the phase transition increased continuously with increasing temperature. Furthermore, critical shear strains comparable to those measured for the shear rate control were obtained for different temperatures. These results suggest that the bilayer fluctuated more easily with increasing temperature, requiring more energy for the phase to transition, as indicated by the stress ramp measurements. Therefore, the temperature-dependent bilayer kinetics determined the conditions required for the phase transition, and shear stress magnitudes required for the phase transition must also be considered in CnEm systems.

Machine learning the metastable phase diagram of covalently bonded carbon

Conventional phase diagram generation involves experimentation to provide an initial estimate of the set of thermodynamically accessible phases and their boundaries, followed by use of phenomenological models to interpolate between the available experimental data points and extrapolate to experimentally inaccessible regions. Such an approach, combined with high throughput first-principles calculations and data-mining techniques, has led to exhaustive thermodynamic databases (e.g. compatible with the CALPHAD method), albeit focused on the reduced set of phases observed at distinct thermodynamic equilibria. In contrast, materials during their synthesis, operation, or processing, may not reach their thermodynamic equilibrium state but, instead, remain trapped in a local (metastable) free energy minimum, which may exhibit desirable properties. Here, we introduce an automated workflow that integrates first-principles physics and atomistic simulations with machine learning (ML), and high-performance computing to allow rapid exploration of the metastable phases to construct “metastable” phase diagrams for materials far-from-equilibrium. Using carbon as a prototypical system, we demonstrate automated metastable phase diagram construction to map hundreds of metastable states ranging from near equilibrium to far-from-equilibrium (400 meV/atom). We incorporate the free energy calculations into a neural-network-based learning of the equations of state that allows for efficient construction of metastable phase diagrams. We use the metastable phase diagram and identify domains of relative stability and synthesizability of metastable materials. High temperature high pressure experiments using a diamond anvil cell on graphite sample coupled with high-resolution transmission electron microscopy (HRTEM) confirm our metastable phase predictions. In particular, we identify the previously ambiguous structure of n-diamond as a cubic-analog of diaphite-like lonsdaelite phase.

Forming mechanism of equilibrium and non-equilibrium metallurgical phases in dissimilar aluminum/steel (Al\u2013Fe) joints

Forming metallurgical phases has a critical impact on the performance of dissimilar materials joints. Here, we shed light on the forming mechanism of equilibrium and non-equilibrium intermetallic compounds (IMCs) in dissimilar aluminum/steel joints with respect to processing history (e.g., the pressure and temperature profiles) and chemical composition, where the knowledge of free energy and atomic diffusion in the Al–Fe system was taken from first-principles phonon calculations and data available in the literature. We found that the metastable and ductile (judged by the presently predicted elastic constants) Al6Fe is a pressure (P) favored IMC observed in processes involving high pressures. The MoSi2-type Al2Fe is brittle and a strong P-favored IMC observed at high pressures. The stable, brittle η-Al5Fe2 is the most observed IMC (followed by θ-Al13Fe4) in almost all processes, such as fusion/solid-state welding and additive manufacturing (AM), since η-Al5Fe2 is temperature-favored, possessing high thermodynamic driving force of formation and the fastest atomic diffusivity among all Al–Fe IMCs. Notably, the ductile AlFe3, the less ductile AlFe, and most of the other IMCs can be formed during AM, making AM a superior process to achieve desired IMCs in dissimilar materials. In addition, the unknown configurations of Al2Fe and Al5Fe2 were also examined by machine learning based datamining together with first-principles verifications and structure predictions. All the IMCs that are not P-favored can be identified using the conventional equilibrium phase diagram and the Scheil-Gulliver non-equilibrium simulations.

Revised α/ε′–γ phase boundaries for the Fe–H system

At high temperatures and high pressures, iron reacts with hydrogen to form hydrides. Three hydride phases are present at moderate temperature and pressure ranges below 2000 K and 20 GPa: α, γ, and ε′ phases, respectively, with bcc, fcc, and double-hcp (dhcp) structures. Recent reports have described studies of phase transitions at temperatures and pressures that differ greatly from those predicted from the conventional phase diagram for the Fe–H system established in the early 2000s. We conducted in-situ X-ray diffraction experiments to investigate α/ε′–γ phase boundaries at temperatures up to 900 K and pressures up to 9.1 GPa. Phase transition temperatures were determined by averaging those observed upon heating and cooling under constant pressure. The α/ε′–γ phase boundaries were found at temperatures 150–300 K higher than the conventional phase boundaries. The α–γ–ε′ triple point was expected to relocate accordingly.

Coexistence of magnetism and superconductivity in the iron containing FeSr2YCu2O7.57 cuprate as studied by μSR

Substitution of copper by iron in the charge reservoir block of the YSr2Cu3O6+δ (YSCO) cuprate superconductor brings out an appealing insight on the interplay between superconductivity and magnetism. In the resulting FeSr2YCu2O7+δ (Fe-1212) materials, FeO1+δ layers and CuO2 bi-layers are alternated along the stacking direction, in close analogy to the RuSr2GdCu2O8 (Ru-1212) ferromagnetic superconductor. For the FeSr2YCu2O7.57 compound, both BVS calculations and spectroscopic data reflect a high doping level in the superconducting planes of pCuO2 ∼ 0.30, placing this cuprate on the overdoped region of the conventional phase diagram for cuprate superconductors. Nonetheless, iron cations in the charge reservoir block (CRB) are quite oxidized, reaching a high formal oxidation state of Fe3.6+. This highly doped FeSr2YCu2O7.57 cuprate is superconducting below Tc = 30 K and, from our muon spin relaxation spectroscopy (μSR) study, the presence of magnetic interactions has been substantiated. Most interestingly, the coincidence of the onset of the magnetic interactions with the superconducting critical temperature suggests a complex interplay between magnetism and superconductivity in this overdoped cuprate.

Hexagonal Close-packed Iron Hydride behind the Conventional Phase Diagram

Hexagonal close-packed iron hydride, hcp FeHx, is absent from the conventional phase diagram of the Fe–H system, although hcp metallic Fe exists stably over extensive temperature (T) and pressure (P) conditions, including those corresponding to the Earth’s inner core. In situ X-ray and neutron diffraction measurements at temperatures ranging from 298 to 1073 K and H pressures ranging from 4 to 7 GPa revealed that the hcp hydride was formed for FeHx compositions when x < 0.6. Hydrogen atoms occupied the octahedral interstitial sites of the host metal lattice both partially and randomly. The hcp hydride exhibited a H-induced volume expansion of 2.48(5) Å3/H-atom, which was larger than that of the face-centered cubic (fcc) hydride. The hcp hydride showed an increase in x with T, whereas the fcc hydride showed a corresponding decrease. The present study provides guidance for further investigations of the Fe–H system over an extensive x–T–P region.

Phenomenological constitutive modeling of ferromagnetic shape memory alloys considering the effects of loading history on reorientation start conditions

Ferromagnetic shape memory alloys (FSMAs) are a branch of smart materials which can undergo inelastic deformation when exposed to magnetic fields. In this work, experiments are carried out on an FSMA consisting of elastic interruptions during reorientation to study the effects of loading history on reorientation start conditions. Correspondingly, a phenomenological approach is introduced to propose appropriate kinetic laws capable of modeling cases in which loading history plays an important role. Conventional phase diagrams in 2D field–stress space are generalized to 3D reorientation surfaces to directly enter the effects of loading history on reorientation start conditions. Algebraic approaches are utilized to find conditions guaranteeing the continuation of variant reorientation. Further experiments are also carried out to verify the proposed model under various incomplete loading–unloading cycles and minor loops. Comparison between numerical and experimental results indicates the validity of the proposed model. Appropriate continuation conditions for the biaxial loading case are proposed, and biaxial results are used to verify the proposed model.

Grain boundary wetting-related phase transformations in Al and Cu-based alloys. Review

The phase transformations can proceed not only between bulk phases but also in free surfaces, grain boundaries and interphase boundaries. In this review we consider the grain boundary phase transformations in Cu- and Al-based alloys. In particular, among those transformations are the transitions between compete and incomplete grain boundary wetting. The wetting phase can be either liquid or solid. If the wetting phase is solid, the portion of wetted grain boundaries can increase also with decreasing temperature. The transition itself can be discontinuous (of the first order) or continous (of the second order). The thin layers of grain boundary phases (called also the grain boundary complexions) can occur in the conditions (temperature, pressure and concentration) where only one volume phase can exist. The phenomenon of the pseudo-incomplete (or pseudo-partial) grain boundary wetting is also discussed. In this case the non-zero grain boundary contact angle coexists with thin layer of grain boundary phase. The new lines of respective grain boundary phase transformations appear in the conventional phase diagrams for three-dimensional phases. The grain boundary phase transitions can strongly influence the properties of grain boundaries themselves and those of polycrystals as a whole. For example, the presence of grain boundary layers can increase the plasticity (if the phase is ductile) or decrease it (of the grain boundary phase is brittle). The influence of grain boundary phase transitions increases with decreasing grain size and becomes critical in nanograined materials.

Effect of loading history on phase transition and martensitic detwinning in shape memory alloys: Limitations of current approaches and development of a 1D constitutive model

Numerous constitutive models have been proposed so far to investigate the unique properties of shape memory alloys. In these models, start conditions for transformation as well as martensitic detwinning are assumed to be independent of loading history. In this work, experiments are carried out on SMA wires and tubes to show how loading history affects the transformation and martensitic detwinning start conditions. Based on the experimental findings, enhanced kinetic laws are proposed to consider the effect of loading history on transformation as well as detwinning start conditions. It is shown that these kinetic laws satisfy the principles of thermodynamics as well. The main feature of the proposed kinetic laws is its simplicity in calculating the amount of martensitic volume fractions. The conventional phase diagrams are further generalized to transformation surfaces in order to directly capture the effects of loading history. For a specified loading history, these surfaces in conjunction with geometrical approaches determine the conditions for the beginning of transformations and detwinning. It is shown that the newly-proposed model can successfully reproduce the experimental findings for various incomplete loading-unloading cycles on SMA wires and tubes.

(Invited) High-k, Higher-k and Ferroelectric HfO2

We have studied high-k gate stacks since 2000. We have presented our results on high-k and also learned a lot at ECS symposium. We gave a talk concerning doped HfO2 in order to achieve higher-k [1], and then also discussed a number of high-k properties including the interface dipole formation at high-k/SiO2 [2], advanced ALD process [3], the interface dipole formation mechanism [4, 5], high-k/Ge gate stacks [6], non-equilibrium PDA-induced HfO2 phase transformation [7], and the interlayer scavenging kinetics in HfO2 gate stacks [8]. In this talk, we would like to look back on our way, and discuss the origin of versatile properties of HfO2. The dielectric constant is important in high-k technology, and ferroelectric HfO2 recently reported is also exciting for functional device applications [9]. Why does HfO2 show such variety of properties? We would like to understand HfO2 in more detail. HfO2 has already been used in advanced CMOS. It is technically important whether a new higher-k material should be searched for or HfO2 should be further used. We have been interested in the structural phase control of HfO2 in order to enhance the dielectric constant. The 1st-principles calculation predicted that high temperature phase HfO2 such as cubic or tetragonal one had higher-k than amorphous or monoclinic one [10]. The monoclinic phase, however, is thermodynamically stable at Si processing temperatures, so usually cubic or tetragonal phase HfO2 is not available. Nevertheless, the significant enhancement of the dielectric constant in HfO2 was experimentally demonstrated through the stabilization of the cubic or tetragonal phase. The trick is the structural phase transformation by doping another metal-oxide to HfO2 [1]. The typical example is Y2O3-doped HfO2. In the ceramics community, it had been actually well recognized since long before that Y2O3 doping could induce the oxygen vacancy in ZrO2 to maintain the charge neutrality, which stabilized the cubic or tetragonal phase [11]. Furthermore, another way to realize the symmetric phase HfO2 was through a non-equilibrium thermal process of amorphous HfO2 [7]. In particular, the fast ramping-up in the RTA process enabled us to achieve the symmetric phase HfO2. It means that the nucleation rather than growth process is more important for implementing high symmetric phase HfO2. In addition, the size effect has also been well investigated thermodynamically for characterizing the structural phase [12]. Very unfortunately for us, we did not notice that HfO2 ferroelectricity came out by doping other oxides. An interesting point in the ferroelectric HfO2 is that the ferroelectric orthorhombic phase is not in the conventional phase diagram. Very recently we found that ferroelectric HfO2 was also made by anion doping into HfO2 [13]. The key is how to realize non-centrosymmetric phase HfO2 structure. Ferroelectric orthorhombic phase might be between monoclinic and tetragonal phases as a metastable state. This makes it more difficult to recognize such unexpected fabulous functionality easily. Materials are so challenging but so exciting.

Novel Electronic State and Superconductivity in the Electron-Doped High-Tc T’-Superconductors

In this review article, we show our recent results relating to the undoped (Ce-free) superconductivity in the electron-doped high- T c cuprates with the so-called T’ structure. For an introduction, we briefly mention the characteristics of the electron-doped T’-cuprates, including the reduction annealing, conventional phase diagram and undoped superconductivity. Then, our transport and magnetic results and results relating to the superconducting pairing symmetry of the undoped and underdoped T’-cuprates are shown. Collaborating spectroscopic and nuclear magnetic resonance results are also shown briefly. It has been found that, through the reduction annealing, a strongly localized state of carriers accompanied by an antiferromagnetic pseudogap in the as-grown samples changes to a metallic and superconducting state with a short-range magnetic order in the reduced superconducting samples. The formation of the short-range magnetic order due to a very small amount of excess oxygen in the reduced superconducting samples suggests that the T’-cuprates exhibiting the undoped superconductivity in the parent compounds are regarded as strongly correlated electron systems, as well as the hole-doped high- T c cuprates. We show our proposed electronic structure model to understand the undoped superconductivity. Finally, unsolved future issues of the T’-cuprates are discussed.

Eclogites and garnet clinopyroxenites in the Anrakhai complex, Central Asian Orogenic Belt, Southern Kazakhstan: P-T evolution, protoliths and some geodynamic implications

The Anrakhai Metamorphic Complex (AMC), located in the SE part of the Chu-Ili Mountains of Southern Kazakhstan in the western part of Central Asian Orogenic Belt, exhibits occurrences of HP metamorphic rocks in the form of eclogites and garnet clinopyroxenites with peak metamorphic conditions of 750–850° and 15–19kbar estimated with both conventional geothermobarometric methods and phase diagram modeling. P-T estimates as well as intimate field relations evidently imply a common metamorphic history for eclogites and garnet clinopyroxenites of the AMC. These high-pressure, medium temperature eclogite facies P-T conditions are indicative of a collision or subduction tectonic setting. Major and trace element geochemistry suggests that they probably had a common magmatic origin as part of a suite of differentiated tholeiitic intrusions. Furthermore, distinctive mineral and chemical compositions of these eclogites and garnet clinopyroxenites correspond to the Fe-Ti type of ultramafic rocks suggesting that they may have been derivatives of intraplate tholeiitic melts, introduced into continental crust before HP metamorphism.

Microstructure and properties of an as-deposited and heat treated martensitic stainless steel fabricated by direct laser deposition

A steel of 16wt.% Cr-4.5wt.% Ni-1.6wt.% Mo-0.9wt.% B-0.6wt.% Mn-0.12wt.%C was fabricated by direct laser deposition (DLD), and its microstructure and material performance were investigated using transmission electron microscope (TEM), scanning electron microscopy (SEM), electrochemical workstation, hardness and impact test machines. The results show that solidification process of the Fe-Cr-Ni-Mo-B steel did not follow the conventional phase diagram during DLD. The as-deposited microstructure consists of a martensite dendritic matrix and lots of lamellar eutectic phases. The lamellar eutectic phase is composed of carboboride and α phase. The carboborides were identified to be Cr-riched M23(C, B)6 with face centered cubic (FCC) structure. Furthermore, the microstructure transition after heat treatment was also studied. After aging treatment, lots of nano-sized secondary carbides were dispersedly precipitated in the martensite matrix with a specific orientation relationship. The hardness is much higher than that of the as-deposited samples, but the toughness is decreased a lot. After destabilization treatment, the content of Cr in the interdendritic eutectic α phase increased and got close to that in the dendritic martensite. The interdendritic eutectic M23(C, B)6 phase tended to be partially dissolved, spheroidized and finally transformed into elliptical-like particles with size of 100–500nm. According to the high-resolution TEM results, the spheroidized carboboride was characterized with long period stacking (LPS) structure along 〈110〉 direction, which has not yet been found in the previous literature. In addition, the evolution of the chemical composition in various phases were also discussed. Due to the evolution of microstructure and chemical composition, both the corrosion resistance and impact toughness were improved significantly.

Surface energy effects on the stability of anatase and rutile nanocrystals: A predictive diagram for Nb2O5-doped-TiO2

Titanium dioxide nanoparticles are widely used for photocatalysis, and the relative fraction of titanium dioxide polymorph, i.e. anatase, rutile, or brookite, significantly affects the final performance. Even though conventional phase diagrams indicate a higher stability for the rutile polymorph, it is well established that nanosizes benefit the anatase phase due to its smaller surface energy. However, doping elements are expected to change this behavior, once changes in both surface and bulk energies may occur. Nb2O5 is commonly added to TiO2 to allow property control. However, the effect of niobium on the relative stability of anatase and rutile phases is not well understood from the thermodynamic point of view. The objective of this work was to build a new predictive nanoscale phase diagram for Nb2O5-doped TiO2. Water adsorption microcalorimetry and high temperature oxide melt solution were used to obtain the surface and bulk enthalpies. The phase diagram obtained shows the stable titania polymorph as a function of the composition and size.

Multiferroic interfaces in bismuth ferrite composite fibers grown by laser floating zone technique

In this work we explore the formation of enhanced multiferroic interfaces in bismuth ferrite crystalline fibers grown by laser floating zone technique. An underlying mechanism of self-segregation during the fibers growth process enables to establish a textured microstructure of a dominant BiFeO3 phase bordered by the presence of Bi25FeO40 secondary phase. The crystallites c axis of the BiFeO3 phase shows a preferential orientation along the longitudinal axis of the fibers, together with grain boundaries that also present a significant alignment with the same direction. These features induce a systematic disturbance of the antiferromagnetic structure of the BiFeO3 phase at the interfaces with the Bi25FeO40 diamagnetic phase. The structural anisotropy confirmed by High Resolution X-ray diffraction and scanning electron microscopy images is also manifested in the magnetic properties of the fibers, which reveal an enhanced susceptibility response in comparison to the conventional BiFeO3 phase diagram.

Influence of the modulated hopping on the one-dimensional interacting electron system

By introducing a modulation parameter (ξ), we study the one-dimensional correlated system with modulated hopping, on-site (U) and nearest-neighbor (V) repulsions in the weak-coupling regime. The induced three-body attraction changes topology of the conventional phase diagram. Besides the usual CDW and SDW phases, a BSDW phase exists for |U−2V|<8tξ2/π. In the absence of V, an insulator–metal transition takes place, and the TS phase is realized for ξ>πU/8t. Phenomenologically, the general quantum phase diagram including insulating and superconducting phases is discussed.

Model of nonadiabatic-to-adiabatic dynamical quantum phase transition in photoexcited systems

We study the ultrafast dynamic process in photoexcited systems and find that the Franck-Condon or Landau-Zener tunneling between the photoexcited state and the ground state is abruptly blocked with increasing the state coupling from nonadiabatic to adiabatic limits. The blockage of the tunneling inhibits the photoexcited state from decaying into the thermalized state and results in an emergence of a metastable state, which represents an entanglement of electronic states with different electron-phonon coupling strengths. Applying this model to the investigation of photoexcited half-doped manganites, we show that the quantum critical transition is responsible for more than three orders of magnitude difference in the ground state recovery times following photoirradiation. This model also explains some elusive experimental results such as photoinduced rearrangement of orbital order by structural rather than electronic process and the structural bottleneck of one-quarter period of the Jahn-Teller mode. We demonstrate that in the spin-boson model there exist unexplored regions not covered in the conventional phase diagram.