Non-equilibrium quantum domain reconfiguration dynamics in a two-dimensional electronic crystal and a quantum annealer.

Relaxation dynamics of complex many-body quantum systems trapped into metastable states is a very active field of research from both the theoretical and experimental point of view with implications in a wide array of topics from macroscopic quantum tunnelling and nucleosynthesis to non-equilibrium superconductivity and energy-efficient memory devices. In this work, we investigate quantum domain reconfiguration dynamics in the electronic superlattice of a quantum material using time-resolved scanning tunneling microscopy and unveil a crossover from temperature to noisy quantum fluctuation dominated dynamics. The process is modeled using a programmable superconducting quantum annealer in which qubit interconnections correspond directly to the microscopic interactions between electrons in the quantum material. Crucially, the dynamics of both the experiment and quantum simulation is driven by spectrally similar pink noise. We find that the simulations reproduce the emergent time evolution and temperature dependence of the experimentally observed electronic domain dynamics.

Manipulation of fractionalized charge in the metastable topologically entangled state of a doped Wigner crystal.

Metastability of many-body quantum states is rare and still poorly understood. An exceptional example is the low-temperature metallic state of the layered dichalcogenide 1T-TaS2 in which electronic order is frozen after external excitation. Here we visualize the microscopic dynamics of injected charges in the metastable state using a multiple-tip scanning tunnelling microscope. We observe non-thermal formation of a metastable network of dislocations interconnected by domain walls, that leads to macroscopic robustness of the state to external thermal perturbations, such as small applied currents. With higher currents, we observe annihilation of dislocations following topological rules, accompanied with a change of macroscopic electrical resistance. Modelling carrier injection into a Wigner crystal reveals the origin of formation of fractionalized, topologically entangled networks, which defines the spatial fabric through which single particle excitations propagate. The possibility of manipulating topological entanglement of such networks suggests the way forward in the search for elusive metastable states in quantum many body systems.

Coherent light control of a metastable hidden state.

Metastable phases present a promising route to expand the functionality of complex materials. Of particular interest are light-induced metastable phases that are inaccessible under equilibrium conditions, as they often host new, emergent properties switchable on ultrafast timescales. However, the processes governing the trajectories to such hidden phases remain largely unexplored. Here, using time- and angle-resolved photoemission spectroscopy, we investigate the ultrafast dynamics of the formation of a hidden quantum state in the layered dichalcogenide 1T-TaS2 upon photoexcitation. Our results reveal the nonthermal character of the transition governed by a collective charge-density-wave excitation. Using a double-pulse excitation of the structural mode, we show vibrational coherent control of the phase-transition efficiency. Our demonstration of exceptional control, switching speed, and stability of the hidden state are key for device applications at the nexus of electronics and photonics.

Cavity-mediated thermal control of metal-to-insulator transition in 1T-TaS2.

Placing quantum materials into optical cavities provides a unique platform for controlling quantum cooperative properties of matter, by both weak and strong light-matter coupling1,2. Here we report experimental evidence of reversible cavity control of a metal-to-insulator phase transition in a correlated solid-state material. We embed the charge density wave material 1T-TaS2 into cryogenic tunable terahertz cavities3 and show that a switch between conductive and insulating behaviours, associated with a large change in the sample temperature, is obtained by mechanically tuning the distance between the cavity mirrors and their alignment. The large thermal modification observed is indicative of a Purcell-like scenario in which the spectral profile of the cavity modifies the energy exchange between the material and the external electromagnetic field. Our findings provide opportunities for controlling the thermodynamics and macroscopic transport properties of quantum materials by engineering their electromagnetic environment.

Optical vortex induced spatio-temporally modulated superconductivity in a high-Tc cuprate.

We report an experimental approach to produce spatially localized photoinduced superconducting state in a cuprate superconductor using optical vortices with ultrafast pulses. The measurements were carried out using coaxially aligned three-pulse time-resolved spectroscopy, in which an intense vortex pulse was used for coherent quenching of superconductivity and the resulting spatially modulated metastable states were analyzed by the pump-probe spectroscopy. The transient response after quenching shows a spatially localized superconducting state that remains unquenched at the dark core of the vortex beam for a few picoseconds. Because the quenching is instantaneously driven by photoexcited quasiparticles, the vortex beam profile can be transferred directly to the electron system. By using the optical vortex-induced superconductor, we demonstrate spatially resolved imaging of the superconducting response and show that the spatial resolution can be improved using the same principle as that of super-resolution microscopy for fluorescent molecules. The demonstration of spatially controlled photoinduced superconductivity is significant for establishing a new method for exploring novel photoinduced phenomena and applications in ultrafast optical devices.

Charge Configuration Memory Devices: Energy Efficiency and Switching Speed.

Current trends in data processing have given impetus for an intense search of new concepts of memory devices with emphasis on efficiency, speed, and scalability. A promising new approach to memory storage is based on resistance switching between charge-ordered domain states in the layered dichalcogenide 1T-TaS2. Here we investigate the energy efficiency scaling of such charge configuration memory (CCM) devices as a function of device size and data write time τW as well as other parameters that have bearing on efficient device operation. We find that switching energy efficiency scales approximately linearly with both quantities over multiple decades, departing from linearity only when τW approaches the ∼0.5 ps intrinsic switching limit. Compared to current state of the art memory devices, CCM devices are found to be much faster and significantly more energy efficient, demonstrated here with two-terminal switching using 2.2 fJ, 16 ps electrical pulses.

Quantum billiards with correlated electrons confined in triangular transition metal dichalcogenide monolayer nanostructures.

Forcing systems through fast non-equilibrium phase transitions offers the opportunity to study new states of quantum matter that self-assemble in their wake. Here we study the quantum interference effects of correlated electrons confined in monolayer quantum nanostructures, created by femtosecond laser-induced quench through a first-order polytype structural transition in a layered transition-metal dichalcogenide material. Scanning tunnelling microscopy of the electrons confined within equilateral triangles, whose dimensions are a few crystal unit cells on the side, reveals that the trajectories are strongly modified from free-electron states both by electronic correlations and confinement. Comparison of experiments with theoretical predictions of strongly correlated electron behaviour reveals that the confining geometry destabilizes the Wigner/Mott crystal ground state, resulting in mixed itinerant and correlation-localized states intertwined on a length scale of 1 nm. The work opens the path toward understanding the quantum transport of electrons confined in atomic-scale monolayer structures based on correlated-electron-materials.

A time-domain phase diagram of metastable states in a charge ordered quantum material.

Metastable self-organized electronic states in quantum materials are of fundamental importance, displaying emergent dynamical properties that may be used in new generations of sensors and memory devices. Such states are typically formed through phase transitions under non-equilibrium conditions and the final state is reached through processes that span a large range of timescales. Conventionally, phase diagrams of materials are thought of as static, without temporal evolution. However, many functional properties of materials arise as a result of complex temporal changes in the material occurring on different timescales. Hitherto, such properties were not considered within the context of a temporally-evolving phase diagram, even though, under non-equilibrium conditions, different phases typically evolve on different timescales. Here, by using time-resolved optical techniques and femtosecond-pulse-excited scanning tunneling microscopy (STM), we track the evolution of the metastable states in a material that has been of wide recent interest, the quasi-two-dimensional dichalcogenide 1T-TaS2. We map out its temporal phase diagram using the photon density and temperature as control parameters on timescales ranging from 10-12 to 103 s. The introduction of a time-domain axis in the phase diagram enables us to follow the evolution of metastable emergent states created by different phase transition mechanisms on different timescales, thus enabling comparison with theoretical predictions of the phase diagram, and opening the way to understanding of the complex ordering processes in metastable materials.

Strain-Induced Metastable Topological Networks in Laser-Fabricated TaS2 Polytype Heterostructures for Nanoscale Devices.

The stacking of layered materials into heterostructures offers diverse possibilities for generating deformed moiré states arising from their mutual interaction. Here we report self-assembled two-dimensional nanoscale strain networks formed within a single prismatic (H) polytype monolayer of TaS2 created in situ on the surface of an orthorhombic 1T-TaS2 single crystal by a low-temperature laser-induced polytype transformation. The networks revealed by scanning tunneling microscopy (STM) take on diverse configurations at different temperatures, including extensive double stripes and a twisted 3-gonal mesh of connected 6-pronged vertices. The resulting phase diagram can be understood to be a consequence of thermally driven minimization of discommensurations between the H and 1T layers. Nontrivial dislocation defects of embedded 2- and 4-gonal structures are shown to be associated with local inhomogeneous strains. The creation of metastable heterostructures by laser quench at cryogenic temperatures in combination with STM manipulation of local strain demonstrates nanoscale control of topological defects in transition metal dichalcogenide heterostructures may be utilized in the fabrication of nanoscale electronic devices and neural networks.

Quantum jamming transition to a correlated electron glass in 1T-TaS2.

Distinct many-body states may be created under non-equilibrium conditions through different ordering paths, even when their constituents are subjected to the same fundamental interactions. The phase-transition mechanism to such states remains poorly understood. Here, we show that controlled optical or electromagnetic perturbations can lead to an amorphous metastable state of strongly correlated electrons in a quasi-two-dimensional dichalcogenide. Scanning tunnelling microscopy reveals a hyperuniform pattern of localized charges, whereas multitip surface nanoscale conductivity measurements and tunnelling spectroscopy show an electronically gapless conducting state that is different from conventional Coulomb glasses and many-body localized systems. The state is stable up to room temperature and shows no signs of either local charge order or phase separation. The mechanism for its formation is attributed to a dynamical localization of electrons through mutual interactions. Theoretical calculations confirm the correlations between localized charges to be crucial for the state's unusual stability.

Histopathologic differentiation as a prognostic factor in patients with carcinoma of the hepatopancreatic ampulla of Vater.

OBJECTIVE: Periampullary carcinomas are a group of neoplasms with variable histopathology that originate from the anatomical junction of different epithelial types including the bile duct, pancreatic duct, and duodenal mucosa. This study was performed to determine whether the histopathologic type of these tumors should be considered an independent prognostic factor. METHODS: We analyzed the specimen histopathology of 37 patients who underwent radical cephalic pancreatoduodenectomy for carcinoma of the ampulla of Vater during a 5-year period. We excluded patients with other tumors with an indication for Whipple's procedure and those in whom R0 resection was not achieved. RESULTS: The carcinomas of the hepatopancreatic ampulla were intestinal in 23 (62%) patients, pancreatobiliary in 13 (35%), and mixed type in 1 (3%). The analysis demonstrated significantly more advanced local tumor spread, a more aggressive lymph node metastasizing pattern, and more frequent lymphatic and perineural invasion in patients with pancreatobiliary than intestinal and mixed type tumors. CONCLUSION: Pancreatobiliary type of ampullary carcinoma is associated with a poorer prognosis than intestinal and mixed types because of its more aggressive behavior. Histopathology should be regarded as an independent predictor of survival and may have therapeutic and prognostic implications for patients.

Large retroperitoneal schwannoma: a rare cause of chronic back pain.

Schwannomas are tumours that arise from Schwann cells of the peripheral nerve sheath and rarely occur in the retroperitoneum. We report a 45-year-old woman who presented with a 2-year history of continuous progressive right-sided lower back and dull flank pain radiating into her posterolateral thigh. Abdominal magnetic resonance imaging showed a homogenous soft-tissue tumour with thick capsular lining, which lay in the right retroperitoneum. The tumour was removed at surgery. A histological examination confirmed the diagnosis of benign encapsulated cellular schwannoma. Complete tumour excision should be regarded as the treatment of choice for benign retroperitoneal schwannomas. Successful treatment of these tumours requires thorough preoperative planning and a multidisciplinary approach.

Nonequilibrium optical control of dynamical states in superconducting nanowire circuits.

Optical control of states exhibiting macroscopic phase coherence in condensed matter systems opens intriguing possibilities for materials and device engineering, including optically controlled qubits and photoinduced superconductivity. Metastable states, which in bulk materials are often associated with the formation of topological defects, are of more practical interest. Scaling to nanosize leads to reduced dimensionality, fundamentally changing the system's properties. In one-dimensional superconducting nanowires, vortices that are present in three-dimensional systems are replaced by fluctuating topological defects of the phase. These drastically change the dynamical behavior of the superconductor and introduce dynamical periodic long-range ordered states when the current is driven through the wire. We report the control and manipulation of transitions between different dynamically stable states in superconducting δ3-MoN nanowire circuits by ultrashort laser pulses. Not only can the transitions between different dynamically stable states be precisely controlled by light, but we also discovered new photoinduced hidden states that cannot be reached under near-equilibrium conditions, created while laser photoexcited quasi-particles are outside the equilibrium condition. The observed switching behavior can be understood in terms of dynamical stabilization of various spatiotemporal periodic trajectories of the order parameter in the superconductor nanowire, providing means for the optical control of the superconducting phase with subpicosecond control of timing.

Markers of proliferation and cytokeratins in the differential diagnosis of jaw cysts.

We conducted a retrospective study to analyze the histologic and immunohistochemical findings in three main types of odontogenic cyst. We studied 90 archived cystic jaw lesions: 30 dentigerous cysts, 30 keratocystic odontogenic tumors, and 30 radicular cysts. The cyst types were identified on the basis of clinical, radiologic, and histopathologic findings. Immunohistochemical analyses included staining with Ki-67, p53, epidermal growth factor receptor (EGFR), cytokeratin (CK) 8, CK14, CK17, and CK18. Cell immunopositivity was evaluated for the entire epithelium. The criteria for Ki-67 and p53 positivity were dense and/or faint nuclear staining, and cells were considered EGFR-positive if they exhibited membrane staining and/or cytoplasm staining. For the cytokeratins, cells exhibiting cytoplasm staining were considered positive. Five representative fields of each lesion were selected and identified in each of the Ki-67- and p53-stained slides. We found a statistically significant difference in the ratio of Ki-67-positive cells in the entire layer between the keratocystic odontogenic tumors and both the dentigerous cysts and the radicular cysts. A statistically significant difference was observed in the ratio of p53-positive cells between the keratocystic odontogenic tumors and the radicular cysts. Cytokeratins proved to be useful in differentiating radicular cysts from other types of cystic jaw lesions because of their CK8-positive and CK17-negative immunolabeling.

Three-dimensional resistivity and switching between correlated electronic states in 1T-TaS2.

Recent demonstrations of controlled switching between different ordered macroscopic states by impulsive electromagnetic perturbations in complex materials have opened some fundamental questions on the mechanisms responsible for such remarkable behavior. Here we experimentally address the question of whether two-dimensional (2D) Mott physics can be responsible for unusual switching between states of different electronic order in the layered dichalcogenide 1T-TaS2, or it is a result of subtle inter-layer "orbitronic" re-ordering of its stacking structure. We report on in-plane (IP) and out-of-plane (OP) resistance switching by current-pulse injection at low temperatures. Elucidating the controversial theoretical predictions, we also report on measurements of the anisotropy of the electrical resistivity below room temperature. From the T-dependence of ρ⊥ and ρ||, we surmise that the resistivity is more consistent with collective motion than single particle diffusive or band-like transport. The relaxation dynamics of the metastable state for both IP and OP electron transport are seemingly governed by the same mesoscopic quantum re-ordering process. We conclude that 1T-TaS2 shows resistance switching arising from an interplay of both IP and OP correlations.

The significance of angiogenesis for predicting optimal therapeutic response in chronic myeloid leukaemia patients.

In this study the correlation and the prognostic value of the morphometric parameters of angiogenesis for optimal therapeutic response to tyrosine kinase inhibitor (TKI) therapy in patients with chronic myeloid leukaemia (CML), i.e. complete cytogenetic response (CCgR) and major molecular response (MMoR), were investigated. Microvascular density (MVD) and a number of different size- and shape-related morphometric parameters of microvessels of bone marrow biopsy from 40 CML patients and 20 controls were examined. Microvessels of bone marrow were examined by using immunohistochemical staining for CD34 and quantified in the region of the most intense vascularisation by using image analysis. CML patients had significantly higher angiogenesis parameters when compared with controls. A statistically significant correlation was found between some parameters of angiogenesis and evaluated CCgR and MMoR. For achievement of CCgR, lower values of MVD, minor axis, area, circularity, and roundness and higher value of aspect ratio, while for achievement of MMoR only lower values of MVD have been identified as positive prognostic factors. Besides confirming increased angiogenesis in CML patients, this study also demonstrated prognostic significance of the degree of angiogenesis for the clinical outcome and identified angiogenic predictive factors for achieving optimal response on TKIs therapy.

Exciton and charge carrier dynamics in few-layer WS2.

Semiconducting transition metal dichalcogenides (TMDs) have been applied as the active layer in photodetectors and solar cells, displaying substantial charge photogeneration yields. However, their large exciton binding energy, which increases with decreasing thickness (number of layers), as well as the strong resonance peaks in the absorption spectra suggest that excitons are the primary photoexcited states. Detailed time-domain studies of the photoexcitation dynamics in TMDs exist mostly for MoS2. Here, we use femtosecond optical spectroscopy to study the exciton and charge dynamics following impulsive photoexcitation in few-layer WS2. We confirm excitons as the primary photoexcitation species and find that they dissociate into charge pairs with a time constant of about 1.3 ps. The better separation of the spectral features compared to MoS2 allows us to resolve a previously undetected process: these charges diffuse through the samples and get trapped at defects, such as flake edges or grain boundaries, causing an appreciable change of their transient absorption spectra. This finding opens the way to further studies of traps in TMD samples with different defect contents.

Central mucoepidermoid carcinoma of the mandible ­ A case report.

Introduction: Mucoepidermoid carcinoma, compared to other tumors of salivary glands, occurs in 5­10% of cases. Histopathologically, it is divided into a well differentiated tumor that is of low-grade of malignancy, and a medium and poorly differentiated tumor of high grade of malignancy. Central mucoepidermoid carcinoma (CMEC) of the mandible was firstly described by Lepp in 1936, on a 66-year-old female patient. CMEC is characterized by atypical clinical image and radiological manifestation. Case Outline: A 55-year-old female patient was examined at the Clinic of Dentistry in Nis, Serbia, with anamnestic data regarding the presence of painless swelling in the right side of the mandible. Considering the histopathological results and presence of enlarged lymph nodes, right hemimandibulectomy and tumour excision from pterygomandibular space followed by supraomohyoid neck dissection was done. In due course, postoperative radiotherapy was applied (60 Gy) Conclusion: CMEC represents a rare tumor, characterized by local tissue destruction and ability to metastasize. Initial biopsy represented the key in preoperative planing. Radical excision with neck lymph node dissection followed by postoperative radiotherapy in our case represent a successful method of treating CMEC of the mandible.

Control of switching between metastable superconducting states in δ-MoN nanowires.

The superconducting state in one-dimensional nanosystems is very delicate. While fluctuations of the phase of the superconducting wave function lead to the spontaneous decay of persistent supercurrents in thin superconducting wires and nanocircuits, discrete phase-slip fluctuations can also lead to more exotic phenomena, such as the appearance of metastable superconducting states in current-bearing wires. Here we show that switching between different metastable superconducting states in δ-MoN nanowires can be very effectively manipulated by introducing small amplitude electrical noise. Furthermore, we show that deterministic switching between metastable superconducting states with different numbers of phase-slip centres can be achieved in both directions with small electrical current pulse perturbations of appropriate polarity. The observed current-controlled bi-stability is in remarkable agreement with theoretically predicted trajectories of the system switching between different limit cycle solutions of a model one-dimensional superconductor.