We present an experimental study of low temperature electronic transport in the hybridization gap of inverted InAs/GaSb composite quantum wells. An electrostatic gate is used to push the Fermi level ...into the gap regime, where the conductance as a function of sample length and width is measured. Our analysis shows strong evidence for the existence of helical edge modes proposed by Liu et al Phys. Rev. Lett. 100, 236601 (2008). Edge modes persist in spite of sizable bulk conduction and show only a weak magnetic field dependence-a direct consequence of a gap opening away from the zone center.
Electron-hole pairing can occur in a dilute semimetal, transforming the system into an excitonic insulator state in which a gap spontaneously appears at the Fermi surface, analogous to a ...Bardeen-Cooper-Schrieffer (BCS) superconductor. Here, we report optical spectroscopic and electronic transport evidence for the formation of an excitonic insulator gap in an inverted InAs/GaSb quantum-well system at low temperatures and low electron-hole densities. Terahertz transmission spectra exhibit two absorption lines that are quantitatively consistent with predictions from the pair-breaking excitation dispersion calculated based on the BCS gap equation. Low-temperature electronic transport measurements reveal a gap of ~2 meV (or ~25 K) with a critical temperature of ~10 K in the bulk, together with quantized edge conductance, suggesting the occurrence of a topological excitonic insulator phase.
We have engineered electron-hole bilayers of inverted InAs/GaSb quantum wells, using dilute silicon impurity doping to suppress residual bulk conductance. We have observed robust helical edge states ...with wide conductance plateaus precisely quantized to 2e^{2}/h in mesoscopic Hall samples. On the other hand, in larger samples the edge conductance is found to be inversely proportional to the edge length. These characteristics persist in a wide temperature range and show essentially no temperature dependence. The quantized plateaus persist to a 12 T applied in-plane field; the conductance increases from 2e^{2}/h in strong perpendicular fields manifesting chiral edge transport. Our study presents a compelling case for exotic properties of a one-dimensional helical liquid on the edge of InAs/GaSb bilayers.
The properties of anyons — two-dimensional particles that are neither fermions nor bosons — have been directly measured in a quantum Hall interferometer.
2019 coronavirus disease (COVID‐19) presents as a newly recognized pneumonia and could rapidly progress into acute respiratory distress syndrome which has brought about a global pandemic. Until now, ...no curative therapy has been strongly recommended for COVID‐19 except for personalized supportive care. T cells and virus‐specific T cells are essential to protect against virus infection, including COVID‐19. Delayed immune reconstitution (IR) and cytokine storm (CS) remain serious obstacles for the cure of COVID‐19. Most COVID‐19 patients, especially among elderly patients, had marked lymphopenia and increased neutrophils, but T cell counts in severe COVID‐19 patients surviving the disease gradually restored later. Elevated pro‐inflammatory cytokines, particularly IL‐6, IL‐10, IL‐2 and IL‐17, and exhausted T cells are found in peripheral blood and the lungs. It suggests that Thymosin α1 and adoptive COVID‐19‐specific T cells could improve IR, while convalescent plasma, IL‐6 blockade, mesenchymal stem cells and corticosteroids could suppress CS. More clinical studies in this field worldwide are urgently warranted to pave the way for therapy of COVID‐19 in the future.
We present an experimental study of S-N-S junctions, with N being a quantum spin Hall insulator made of InAs/GaSb. A front gate is used to vary the Fermi level into the minigap, where helical edge ...modes exist Phys. Rev. Lett. 107, 136603 (2011). In this regime we observe a ~2e(2)/h Andreev conductance peak, consistent with a perfect Andreev reflection on the helical edge modes predicted by theories. The peak diminishes under a small applied magnetic field due to the breaking of time-reversal symmetry. This work thus demonstrates the helical property of the edge modes in a quantum spin Hall insulator.
Correlation and frustration play essential roles in physics, giving rise to novel quantum phases
. A typical frustrated system is correlated bosons on moat bands, which could host topological orders ...with long-range quantum entanglement
. However, the realization of moat-band physics is still challenging. Here, we explore moat-band phenomena in shallowly inverted InAs/GaSb quantum wells, where we observe an unconventional time-reversal-symmetry breaking excitonic ground state under imbalanced electron and hole densities. We find that a large bulk gap exists, encompassing a broad range of density imbalances at zero magnetic field (B), accompanied by edge channels that resemble helical transport. Under an increasing perpendicular B, the bulk gap persists, and an anomalous plateau of Hall signals appears, which demonstrates an evolution from helical-like to chiral-like edge transport with a Hall conductance approximately equal to e
/h at 35 tesla, where e is the elementary charge and h is Planck's constant. Theoretically, we show that strong frustration from density imbalance leads to a moat band for excitons, resulting in a time-reversal-symmetry breaking excitonic topological order, which explains all our experimental observations. Our work opens up a new direction for research on topological and correlated bosonic systems in solid states beyond the framework of symmetry-protected topological phases, including but not limited to the bosonic fractional quantum Hall effect.
•Novel approach for high-strength pharmaceutical wastewater by PD/A was confirmed.•PD/A biofilm was developed rapidly and had high tolerance to real wastewater.•Higher LB-EPS was produced with ...protein 3-turn helices structure was obtained.•Relatively stable TN removal efficiency of 81.2% was achieved with increasing load.•Thauera was highly enriched and dominated for partial NO3− reduction to NO2−.
Biological nitrogen removal from pharmaceutical wastewater has drawn increasing attention due to biotoxicity and inhibition. In this study, for the first time, a novel approach integrating partial-denitrification with anaerobic ammonia oxidation (PD/A) in a sequencing biofilm batch reactor (SBBR) was proposed and demonstrated to be efficient to treat the bismuth nitrate and bismuth potassium citrate manufacturing wastewater, containing ammonia (NH4+-N) and nitrate (NO3−-N) of 6300±50 mg L − 1 and 15,300±50 mg L − 1. The maximum anammox activity was found at the shock effect of influent total nitrogen (TN) of 100 mg L − 1 with NO3−-N/NH4+-N of 1.0. Long-term operation demonstrated that the PD/A biofilm was developed rapidly after 30 days using synthetic influent, with TN removal efficiency increasing from 40.9% to 80.8%. Significantly, the key bacteria for PD/A had high tolerance and adapted rapidly to pharmaceutical wastewater, achieving a relatively stable TN removal efficiency of 81.2% with influent NH4+-N and NO3−-N was 77.9 ± 2.6 and 104.1 ± 4.4 mg L − 1 at a relatively low COD/NO3−-N of 2.6. Anammox pathway contributed to TN removal reached 83.6%. Significant increase of loosely-bound extracellular polymeric substances was obtained with increasing protein of 3-turn helices structure as response to the inhibitory condition. High-throughput sequencing analysis revealed that the functional genus Thauera was highly enriched in both biofilms (9.5%→43.6%) and suspended biomass (15.5%→57.5%), which played a key role in high NO2−-N accumulation. While the anammox bacteria decreasing from 7.8% to 1.6% in biofilm, and from 1.8% decreased to 0.1% in the suspended sludge. Overall, this study provides a new method of high-strength pharmaceutical wastewater treatment with low energy consumption and operation cost, as well as a satisfactory efficiency.
Display omitted
Display omitted
•Effluent TN as low as 4.0 mg N/L was achieved via PD-Anammox process.•Anammox was stable and accounted for 78.2% on nitrogen removal.•Low nitrous oxide (N2O) was produced in ...PD-Anammox process.•Oxygen consumption, COD demand and sludge production would be largely reduced.•PD-Anammox process can be easily retrofitted from existing plants.
High nitrate (NO3−-N) concentration in the effluent of wastewater treatment plants (WWTPs), cannot meet the increasing stringent discharge limits. Hence, the tertiary treatment is necessary to lower the total nitrogen concentration. In this study, an innovative partial denitrification (PD)-Anammox process was applied to remove the nitrate nitrogen (20–40 mg N/L) from secondary effluent. The nitrate wastewater were firstly fed to PD sequencing batch reactor (SBR, 10 L) to produce nitrite along with the low carbon/nitrogen ratio (C/N) municipal sewage (NH4+ of 57.8 mg N/L, COD of 175.8 mg/L), then the effluent from SBR was pumped to the anaerobic sludge blanket (UASB, 3.2 L) performing anammox for further nitrogen removal. The integrated process was operated for 224 days with the secondary effluent to municipal sewage volume ratio of 2.9–6. The results suggested that an excellent nitrate removal efficiency of 97.9% was achieved, and the mean removal efficiency of NH4+-N and COD from municipal sewage were 95.2% and 81.6%, respectively, leading to the total nitrogen and COD concentration in the final effluent as low as 4.0 mg N/L and 30.1 mg/L, respectively. Anammox was the main nitrogen removal pathway with a mean proportion of 78.2%, and Candidatus_Brocadia was identified as the dominating genus. Furthermore, it was found that a minor nitrous oxide (N2O) was produced in the integrated process. The PD-Anammox process was verified to be economically and environmentally feasible for retrofitting of existing plants.
PDF
