82 research outputs found
Superconductivity of Strontium Titanate in Reduced Dimensions
In this thesis, I will summarize my work on mesoscale devices created at the hetero interface between complex oxides lanthanum aluminate and strontium titanate (LaAlO3/SrTiO3). In chapter I, the relevant advances in the field of SrTiO3 as well as LaAlO3/SrTiO3 is reviewed. In chapter II, I will briefly describe relevant experimental setups and techniques, from transport at milliKelvin (mK) temperatures to our efforts on mK scanning probe and mK optical characterization of the system. In chapter III, I will summarize our observation of 1D nature of the superconductivity at LaAlO3 /SrTiO3. In chapter IV, results from 1D zigzag superconducting nanowires are summarized. In chapter V, I will summarize our simulation work on phase field modeling SrTiO3, followed by future works and outlook for this field in chapter VI
Surface acoustic wave generation and detection in quantum paraelectric regime of SrTiO-based heterostructure
Strontium titanate (STO), apart from being a ubiquitous substrate for
complex-oxide heterostructures, possesses a multitude of strongly-coupled
electronic and mechanical properties. Surface acoustic wave (SAW) generation
and detection offers insight into electromechanical couplings that are
sensitive to quantum paraelectricity and other structural phase transitions.
Propagating SAWs can interact with STO-based electronic nanostructures, in
particular LaAlO/SrTiO (LAO/STO). Here we report generation and
detection of SAW within LAO/STO heterointerfaces at cryogenic temperatures
(~2 K) using superconducting interdigitated transducers (IDTs). The
temperature dependence shows an increase in the SAWs quality factor that
saturates at K. The effect of backgate tuning on the SAW
resonance frequency shows the possible acoustic coupling with the ferroelastic
domain wall evolution. This method of generating SAWs provides a pathway
towards dynamic tuning of ferroelastic domain structures, which are expected to
influence electronic properties of complex-oxide nanostructures. Devices which
incorporate SAWs may in turn help to elucidate the role of ferroelastic domain
structures in mediating electronic behavior
Monolayer superconductivity and tunable topological electronic structure at the Fe(Te,Se)/Bi2Te3 interface
The interface between two-dimensional topological Dirac states and an s-wave
superconductor is expected to support Majorana bound states that can be used
for quantum computing applications. Realizing these novel states of matter and
their applications requires control over superconductivity and spin-orbit
coupling to achieve spin-momentum locked topological surface states which are
simultaneously superconducting. While signatures of Majorana bound states have
been observed in the magnetic vortex cores of bulk FeTe0.55Se0.45,
inhomogeneity and disorder from doping makes these signatures unclear and
inconsistent between vortices. Here we report superconductivity in monolayer
FeTe1-ySey (Fe(Te,Se)) grown on Bi2Te3 by molecular beam epitaxy. Spin and
angle resolved photoemission spectroscopy directly resolve the interfacial spin
and electronic structure of Fe(Te,Se)/Bi2Te3 heterostructures. We find that for
y = 0.25 the Fe(Te,Se) electronic structure overlaps with the topological
Bi2Te3 interfacial states which disrupts the desired spin-momentum locking. In
contrast, for y = 0.1 a smaller Fe(Te,Se) Fermi surface allows for clear
spin-momentum locking observed in the topological states. Hence, we demonstrate
the Fe(Te,Se)/Bi2Te3 system is a highly tunable platform for realizing Majorana
bound states where reduced doping can improve characteristics important for
Majorana interrogation and potential applications
A Reconfigurable Quantum Local Area Network Over Deployed Fiber
Practical quantum networking architectures are crucial for scaling the
connection of quantum resources. Yet quantum network testbeds have thus far
underutilized the full capabilities of modern lightwave communications, such as
flexible-grid bandwidth allocation. In this work, we implement flex-grid
entanglement distribution in a deployed network for the first time, connecting
nodes in three distinct campus buildings time-synchronized via the Global
Positioning System (GPS). We quantify the quality of the distributed
polarization entanglement via log-negativity, which offers a generic metric of
link performance in entangled bits per second. After demonstrating successful
entanglement distribution for two allocations of our eight dynamically
reconfigurable channels, we demonstrate remote state preparation -- the first
realization on deployed fiber -- showcasing one possible quantum protocol
enabled by the distributed entanglement network. Our results realize an
advanced paradigm for managing entanglement resources in quantum networks of
ever-increasing complexity and service demands
Original Research MicroRNA-30a promotes invasiveness and metastasis in vitro and in vivo through epithelial-mesenchymal transition and results in poor survival of nasopharyngeal carcinoma patients
Abstract Although microRNA-30a (miR-30a) has been shown to regulate cancer metastasis, the molecular mechanism has not yet been clearly elucidated in nasopharyngeal carcinoma (NPC). The present study was to investigate the miR-30a expression pattern and its potential functions and further to identify its target gene and corresponding clinical applications in NPC. MiR-30a was identified to be down-regulated in NPC primary tumors compared with metastatic tumors using quantitative real-time PCR. Furthermore, over-expression of miR-30a transfected with precursor increased the ability of metastasis and invasion of NPC tumor cells in vivo and in vitro. E-cadherin was screened as a putative target gene of miR-30a by computational algorithms. Luciferase reporter assays showed that over-expression of miR-30a directly reduced the activity of a luciferase transcript combined with the 3 0 -untranslated region (3 0 -UTR) of E-cadherin. Kaplan-Meier survival analysis and log-rank test were analyzed for 1077 NPC patients for overall survival, indicating that a high expression of E-cadherin was beneficial for NPC prognosis (P ¼ 0.001). Importantly, NPC patients with high expression of E-cadherin had much lower risk of poor prognosis (hazard ratio ¼ 0.757, P ¼ 0.017) using multivariate analysis. In conclusion, miR-30a could play an important role in regulating NPC metastasis and potentially provide useful guidelines for individualized therapy
The Role of Age in Predicting the Outcome of Caustic Ingestion in Adults: A Retrospective Analysis
<p>Abstract</p> <p>Background</p> <p>Although the outcomes of caustic ingestion differ between children and adults, it is unclear whether such outcomes differ among adults as a function of their age. This retrospective study was performed to ascertain whether the clinical outcomes of caustic ingestion differ significantly between elderly and non-elderly adults.</p> <p>Methods</p> <p>Medical records of patients hospitalized for caustic ingestion between June 1999 and July 2009 were reviewed retrospectively. Three hundred eighty nine patients between the ages of 17 and 107 years were divided into two groups: non-elderly (< 65 years) and elderly (≥ 65 years). Mucosal damage was graded using esophagogastroduodenoscopy (EGD). Parameters examined in this study included gender, intent of ingestion, substance ingested, systemic and gastrointestinal complications, psychological and systemic comorbidities, severity of mucosal injury, and time to expiration.</p> <p>Results</p> <p>The incidence of psychological comorbidities was higher for the non-elderly group. By contrast, the incidence of systemic comorbidities, the grade of severity of mucosal damage, and the incidence of systemic complications were higher for the elderly group. The percentages of ICU admissions and deaths in the ICU were higher and the cumulative survival rate was lower for the elderly group. Elderly subjects, those with systemic complications had the greatest mortality risk due to caustic ingestion.</p> <p>Conclusions</p> <p>Caustic ingestion by subjects ≥65 years of age is associated with poorer clinical outcomes as compared to subjects < 65 years of age; elderly subjects with systemic complications have the poorest clinical outcomes. The severity of gastrointestinal tract injury appears to have no impact on the survival of elderly subjects.</p
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