Superconductivity and Charge-Density-Wave-Like Transition in Th2Cu4As5

We report the synthesis, crystal structure, and physical properties of a novel ternary compound, Th2Cu4As5. The material crystallizes in a tetragonal structure with lattice parameters a = 4.0639(3) Å and c = 24.8221(17) Å. Its structure can be described as an alternating stacking of fluorite-type Th2As2 layers with antifluorite-type double-layered Cu4As3 slabs. The measurement of electrical resistivity, magnetic susceptibility, and specific heat reveals that Th2Cu4As5 undergoes bulk superconducting transition at 4.2 K. Additionally, all these physical quantities exhibit anomalies at 48 K, accompanied by a sign change in the Hall coefficient, suggesting a charge-density-wave-like (CDW) phase transition. Drawing from both experimental data and band calculations, we propose that the superconducting and CDW-like phase transitions are, respectively, associated with the Cu4As3 slabs and the As plane in the Th2As2 layers.

Time-reversal symmetry breaking superconductivity between twisted cuprate superconductors

Twisted interfaces between stacked van der Waals (vdW) cuprate crystals present a platform for engineering superconducting order parameters by adjusting stacking angles. Using a cryogenic assembly technique, we construct twisted vdW Josephson junctions (JJs) at atomically sharp interfaces between Bi2Sr2CaCu2O8+x crystals, with quality approaching the limit set by intrinsic JJs. Near 45° twist angle, we observe fractional Shapiro steps and Fraunhofer patterns, consistent with the existence of two degenerate Josephson ground states related by time-reversal symmetry (TRS). By programming the JJ current bias sequence, we controllably break TRS to place the JJ into either of the two ground states, realizing reversible Josephson diodes without external magnetic fields. Our results open a path to engineering topological devices at higher temperatures.

Tumor Treatment Response Assessed During the Concurrent Chemoradiotherapy for Nasopharyngeal Patients

PURPOSE/OBJECTIVE(S)

To evaluate intratumoral treatment response distribution with using FDG-PET/CT during the chemoradiotherapy of nasopharyngeal patients (NPC).

MATERIALS/METHODS

A total of 5 of 30 patients with stage III-IVA NPC were enrolled in the institutional protocol for induction/concurrent chemoradiotherapy with radiation dose of 70 Gy in 33 fractions. For each patient, a pre-radiation treatment FDG-PET/MRI image (SUV0) and a mid-treatment image (SUVm) at the treatment dose of 31.8 Gy were obtained. Followed by deformable PET/MRI registration between SUV0 and SUVm, the tumor voxel SUV reduction ratio was obtained to construct a tumor dose response matrix (DRM). Tumor SUVavid was also constructed by limiting tumor voxel SUVm > a given value. Spatial correlations of the tumor SUV0, SUVm, SUVavid and DRM were determined.

RESULTS

The mean and coefficient variation (CV) of the SUV0, SUVm and DRM for all tumors were 5.05 (52%), 2.72 (49%) and 0.64 (63%) (Table contains the individual data), which were smaller than those on the SUVs of head-n-neck HPV+ patients reported previously due to the induction chemotherapy, but had much larger DRM mean and CV. The inter-tumoral CVs of SUV0 and DRM were 29% and 27%, which were much lower than those of the intra-tumoral CVs 43% and 57%. Meanwhile, the intra-tumoral variations on SUV0 was smaller than the one of head-neck HPV+ patients, but the DRM intra-variation was much larger. There was a weak correlation between SUV0 and SUVm with the correlation coefficient 0.13, a medium correlation of -0.55 between SUV0 and DRM, but a strong correlation, 0.72, between SUVm and DRM. However, the spatial correlation between tumor DRM and SUVavid was getting weaker as the SUVavid value increasing and equal 0.47 with SUVavid value > 3.

CONCLUSION

The spatial dose response DRM for NPC in the concurrent chemoradiotherapy was relatively high, while had relatively low baseline tumor metabolic activity SUV0. It was most likely due to the induction chemotherapy. In addition, the tumor dose response showed vary large intra-tumoral variation. The high correlations between DRM and SUVm imply that SUVavid could be used partially to guide adaptive modification of NPC treatment with carefully selected boundary value.

Tumor Treatment Response Assessed During the Chemo-Radiotherapy for Locally Advanced NSCLC

PURPOSE/OBJECTIVE(S)

To evaluate the capability of assessing intratumoral treatment response distribution with using FDG-PET/CT during the chemoradiotherapy of locally advanced NSCLC.

MATERIALS/METHODS

Twelve of total 50 patients with stage III NSCLC were enrolled in the institutional protocol for concurrent chemoradiotherapy with treatment dose of 54-60 Gy in 27-30 fractions. For each patient, a pre-treatment FDG-PET/CT image (SUV0) and a mid-treatment image (SUVm) obtained within the treatment dose of 24 ∼ 46 Gy were obtained. Followed by deformable PET/CT registration between SUV0 and SUVm, the tumor voxel SUV reduction ratio was obtained to construct a tumor dose response matrix (DRM). Tumor SUVavid was also constructed by limiting tumor voxel SUVm > a given value. Spatial correlations of the tumor SUV0, SUVm, SUVavid and DRM were determined.

RESULTS

The mean and coefficient variation (CV) of the SUV0, SUVm and DRM for all tumors were 6.56(64%), 2.82(59%) and 0.52(70%) (Table contains the individual data), which were like those on the SUVs and the mean DRM of head-neck HPV- patients reported previously, but much larger on the DRM variation. The inter-tumoral CVs of SUV0 and DRM were 17% and 43%, which were much smaller than those of the intra-tumoral CVs 61% and 55%. Meanwhile, the intra-tumoral variations on both SUV0 and DRM were much larger than those of head-neck HPV- patients. There was a weak correlation between SUV0 and SUVm with the correlation coefficient 0.32, a medium correlation of -0.51 between SUV0 and DRM; 0.58 between SUVm and DRM. It implies that the rule of tumor dose response DRM on treatment modification decision cannot be fully replaced by either SUV0 or SUVm. The spatial correlation between tumor DRM and SUVavid was 0.23 with SUVavid value > 3, which was getting weaker when increasing SUVavid value.

CONCLUSION

Spatial dose response for NSCLC assessed using FDG-PET/CT feedback demonstrated high treatment resistant patterns, which had a large intra-tumoral variation. In addition, the medium correlations of DRM vs SUV0 and DRM vs SUVm imply that all these factors could be used to guide adaptive modification of NSCLC treatment.

Hybrid Immuno-RT for Bulky Tumors: Standard Fractionation with Partial Tumor SBRT

PURPOSE/OBJECTIVE(S)

Bulky tumors remain challenging to be treated. Stereotactic body radiation therapy (SBRT) is effective against radioresistant tumor cells and can induce immunogenic cell death (ICD) that leads to T-cell-mediated antitumor effects. Low-dose radiation (LDRT) can inflame the tumor microenvironment (TME) by recruiting T cells. We designed a novel radiotherapy technique (RT, ERT) whose dose distribution map resembles the "eclipse" by concurrently delivering LDRT to the whole tumor, meanwhile SBRT to only a part of the same tumor. This study examined the safety and efficacy of ERT to bulky lesions with PD-1 inhibitors in mice and patients.

MATERIALS/METHODS

In mice with CT26 colon or LLC1 lung bulky tumors (400 - 500 cm3), the whole tumor was irradiated by LDRT (2 Gy x 3), meanwhile the tumor center was irradiated by SBRT (10 Gy x 3); αPD-1 was given weekly. The dependence of therapeutic effects on CD8+ T cells was determined using depleting antibodies. Frequencies of CD8+ T cells and M1 macrophages (Mφ) were determined by flow cytometry. Multiplex Immunohistochemistry (mIHC) was applied to analyze the number and the location of CD8+ T cells and their subpopulations, as well as the phospho-eIF2α level (the ICD marker) of tumor cells in TME. Patients with advanced lung or liver bulky tumors who failed standard treatment or with oncologic emergencies were treated. Kaplan-Meier method was applied to estimate patients' progression-free survival (PFS) and overall survival (OS).

RESULTS

ERT/αPD-1 is superior to SBRT/αPD-1 or LDRT/αPD-1 in controlling bulky tumors in both mouse models in a CD8+ T-cell dependent manner. In the CT26 model, ERT/αPD-1 resulted in complete tumor regression in 3/11 mice and induced more CD8+ T cells and M1 Mφ in TME compared to other groups. mIHC analysis showed that ERT/αPD-1 induced higher bulk, stem-like (TCF1+ TIM3- PD-1+), and more differentiated (TCF1- TIM3+ PD-1+) CD8+ T cells infiltration into the tumor center and periphery compared to other groups. Compared to untreated or LDRT-treated tumor centers, tumor centers irradiated with ERT or SBRT showed elevated phospho-eIF2α accompanied by higher dendritic cell infiltration. In total, 39 advanced cancer patients were treated with ERT/αPD-1 or plus chemotherapy. Radiation-induced pneumonitis occurred in 1 of 26 patients receiving thoracic ERT. There were two cases of grade III toxicity associated with PD-1 inhibitors. No toxicity above grade III was observed. The objective response rate was 38.5%. The median PFS was 5.6 months and median OS was not reached at a median follow-up of 11.7 months.

CONCLUSION

ERT/αPD-1 showed superior efficacy in controlling bulky tumor in two mouse models. The hybrid immuno-RT (ERT) combing PD-1 inhibitors was safe and effective in patients with bulky tumors. Further clinical trials in combination with bioimaging to identify the optimal SBRT target region for the bulky tumor are warranted.

Low-energy quasi-circular electron correlations with charge order wavelength in Bi2Sr2CaCu2O8+δ

Most resonant inelastic x-ray scattering (RIXS) studies of dynamic charge order correlations in the cuprates have focused on the high-symmetry directions of the copper oxide plane. However, scattering along other in-plane directions should not be ignored as it may help understand, for example, the origin of charge order correlations or the isotropic scattering resulting in strange metal behavior. Our RIXS experiments reveal dynamic charge correlations over the q_x-q_y scattering plane in underdoped Bi₂Sr₂CaCu₂O_8+δ. Tracking the softening of the RIXS-measured bond-stretching phonon, we show that these dynamic correlations exist at energies below approximately 70 meV and are centered around a quasi-circular manifold in the q_x-q_y scattering plane with radius equal to the magnitude of the charge order wave vector, q_CO. This phonon-tracking procedure also allows us to rule out fluctuations of short-range directional charge order (i.e., centered around [q_x = ±q_CO, q_y = 0] and [q_x = 0, q_y = ±q_CO]) as the origin of the observed correlations.

A magnetic continuum in the cobalt-based honeycomb magnet BaCo2(AsO4)2

Quantum spin liquids (QSLs) are topologically ordered states of matter that host fractionalized excitations. A particular route towards a QSL is via strongly bond-dependent interactions on the hexagonal lattice. A number of Ru- and Ir-based candidate Kitaev QSL materials have been pursued, but all have appreciable non-Kitaev interactions. Using time-domain terahertz spectroscopy, we observed a broad magnetic continuum over a wide range of temperatures and fields in the honeycomb cobalt-based magnet BaCo₂(AsO₄)₂, which has been proposed to be a more ideal version of a Kitaev QSL. Applying an in-plane magnetic field of ~0.5 T suppresses the magnetic order, and at higher fields, applying the field gives rise to a spin-polarized state. Under a 4 T magnetic field that was oriented principally out of plane, a broad magnetic continuum was observed that may be consistent with a field-induced QSL. Our results indicate BaCo₂(AsO₄)₂ is a promising QSL candidate.

Safety and efficacy of dendritic cell-based immunotherapy (DCVAC/LuCa) combined with carboplatin/pemetrexed for patients with advanced non-squamous non-small-cell lung cancer without oncogenic drivers

Background

Our prospective, open-label, single-arm phase II study investigated the safety and efficacy of DCVAC/LuCa (dendritic cell vaccines for lung cancer) combined with standard carboplatin/pemetrexed in advanced non-squamous (nsq) non-small-cell lung cancer (NSCLC).

Patients and methods

Eligible patients had stage IV nsq NSCLC without oncogenic drivers and had not received prior systemic cancer therapy. Treatment consisted of carboplatin/pemetrexed for up to 6 cycles followed by 21 cycles of pemetrexed maintenance or until progression or intolerance. Non-progression patients after two cycles of chemotherapy started to receive DCVAC/LuCa subcutaneously (s.c.) on day 15 of cycle 3, and thereafter q3w (day 15 of chemotherapy cycles) for up to 15 doses. Dosing of DCVAC/LuCa s.c. varied among patients depending on the baseline number of leucocytes but remained constant for each single patient. Safety was assessed by adverse events (AEs), treatment-related adverse events (TRAEs), serious adverse events (SAEs), and adverse events of special interest (AESIs). Efficacy was measured by overall survival (OS), progression-free survival (PFS), time to progression (TTP), and objective response rate (ORR).

Results

Sixty-one patients were enrolled. In the safety population (n = 60), eight patients (13.33%) had grade 3 or greater TRAEs, and six patients (10.0%) showed SAEs which were not related to leukapheresis or DC vaccination. Six grade 1 AEs were considered to be related to leukapheresis. No AESIs or DCVAC/LuCa-induced AEs were observed. The 2-year survival rate in the modified intention-to-treat population (n = 44) was 52.57%. Median OS was not reached. Median PFS was 8.0 months, median TTP was 10.2 months, and the ORR was 31.82%.

Conclusion

In treatment-naïve stage IV nsq NSCLC patients without oncogenic drivers, the combination of carboplatin/pemetrexed and DCVAC/LuCa was well tolerated and showed promising efficacy. Therefore, a study to prove our immunotherapeutic concept in a randomized phase III trial is planned.

•

We investigated the safety and efficacy of DCVAC/LuCa combined with standard carboplatin/pemetrexed in nsq NSCLC.

•

The combination therapy showed a favorable tolerability profile in a selected Chinese population.

•

The 2-year survival rate in the modified intention-to-treat population (n = 44) was 52.57%.

Observation of magnetic adatom-induced Majorana vortex and its hybridization with field-induced Majorana vortex in an iron-based superconductor

Braiding Majorana zero modes is essential for fault-tolerant topological quantum computing. Iron-based superconductors with nontrivial band topology have recently emerged as a surprisingly promising platform for creating distinct Majorana zero modes in magnetic vortices in a single material and at relatively high temperatures. The magnetic field-induced Abrikosov vortex lattice makes it difficult to braid a set of Majorana zero modes or to study the coupling of a Majorana doublet due to overlapping wave functions. Here we report the observation of the proposed quantum anomalous vortex with integer quantized vortex core states and the Majorana zero mode induced by magnetic Fe adatoms deposited on the surface. We observe its hybridization with a nearby field-induced Majorana vortex in iron-based superconductor FeTe0.55Se0.45. We also observe vortex-free Yu-Shiba-Rusinov bound states at the Fe adatoms with a weaker coupling to the substrate, and discover a reversible transition between Yu-Shiba-Rusinov states and Majorana zero mode by manipulating the exchange coupling strength. The dual origin of the Majorana zero modes, from magnetic adatoms and external magnetic field, provides a new single-material platform for studying their interactions and braiding in superconductors bearing topological band structures.

Spin-Polarized Yu-Shiba-Rusinov States in an Iron-Based Superconductor

Yu-Shiba-Rusinov (YSR) bound states appear when a magnetic atom interacts with a superconductor. Here, we report on spin-resolved spectroscopic studies of YSR states related with Fe atoms deposited on the surface of the topological superconductor FeTe_{0.55}Se_{0.45} using a spin-polarized scanning tunneling microscope. We clearly identify the spin signature of pairs of YSR bound states at finite energies within the superconducting gap having opposite spin polarization as theoretically predicted. In addition, we also observe zero-energy bound states for some of the adsorbed Fe atoms. In this case, a spin signature is found to be absent indicating the absence of Majorana bound states associated with Fe adatoms on FeTe_{0.55}Se_{0.45}.

Gen-editing to model Short QT syndrome type 5 using human-induced pluripotent stem cell-derived cardiomyocytes

Aims

Short QT syndrome (SQTS), a disorder associated with characteristic electrocardiogram QT-segment abbreviation, predisposes afflicted patients to sudden cardiac death. Despite some progress in assessing the organ level pathophysiology and genetic changes of the disorder, the understanding of the human cellular phenotype and discovering of an optimal therapy has lagged due to a lack of appropriate human cellular models of the disorder. The aim of this study was to establish a cellular model of SQTS type 5 using human-induced pluripotent stem cell–derived cardiomyocytes (hiPSC-CMs) and gene-edited cell line using CRISPR/CAS9.

Methods and results

This study recruited one patient with short QT syndrome type 5 carrying a mutation in CACNb2 gene as well as one healthy control subject. We generated hiPSCs from their skin fibroblasts, and differentiated hiPSCs into cardiomyocytes (hiPSC-CMs) for physiological. Isogenic control hiPSC-CMs generated by the CRISPR/CAS9 technique were also used for the study.

The hiPSC-CMs from the patient showed a reduced calcium current (ICa-L) density and shortened action potential duration (APD) compared with healthy control hiPSC-CMs and isogenic hiPSC-CMs. Furthermore, they demonstrated abnormal rhythmic activities. Carbachol increased the arrhythmic events in SQTS significantly but not in healthy and isogenic control cells. Gene and protein expression profiling showed a decreased CACNb2 expression in SQTS cells. Quinidine prolonged the APD and abolished arrhythmic activity.

Conclusions

Patient-specific hiPSC-CMs are able to recapitulate single-cell phenotype features of SQTS type 5 and provide novel opportunities to further elucidate the cellular disease mechanism and test drug effects.

Funding Acknowledgement

Type of funding source: None

Immune cell infiltration features and related marker genes in lung cancer based on single-cell RNA-seq

PURPOSE

Immune cells in the immune microenvironment of lung cancer have a great impact on the development of lung cancer. Our purpose was to analyze the immune cell infiltration features and related marker genes for lung cancer.

METHODS

Single cell RNA sequencing data of 11,485 lung cancer cells were retrieved from the Gene Expression Omnibus. After quality control and data normalization, cell clustering was performed using the Seurat package. Based on the marker genes of each cell type from the CellMarker database, each cell was divided into G1, G2M, and S phases. Then, differential expression and functional enrichment analyses were performed. CIBERSORT was used to reconstruct immune cell types.

RESULTS

Following cell filtering, highly variable genes were identified for all cells. 14 cell types were clustered. Among them, CD4 + T cell, B cell, plasma cell, natural killer cell and cancer stem cell were the top five cell types. Up-regulated genes were mainly enriched in immune-related biological processes and pathways. Using CIBERSORT, we identified the significantly higher fractions of naïve B cell, memory CD4 + T cell, T follicular helper cell, T regulatory helper cell and M1 macrophage in lung cancer tissues compared to normal tissues. Furthermore, the fractions of resting NK cell, monocyte, M0 macrophage, resting mast cell, eosinophil and neutrophil were significantly lower in tumor tissues than normal tissues.

CONCLUSION

Our findings dissected the immune cell infiltration features and related marker genes for lung cancer, which might provide novel insights for the immunotherapy of lung cancer.

A cleanroom in a glovebox

The exploration of new materials, novel quantum phases, and devices requires ways to prepare cleaner samples with smaller feature sizes. Initially, this meant the use of a cleanroom that limits the amount and size of dust particles. However, many materials are highly sensitive to oxygen and water in the air. Furthermore, the ever-increasing demand for a quantum workforce, trained and able to use the equipment for creating and characterizing materials, calls for a dramatic reduction in the cost to create and operate such facilities. To this end, we present our cleanroom-in-a-glovebox, a system that allows for the fabrication and characterization of devices in an inert argon atmosphere. We demonstrate the ability to perform a wide range of characterization as well as fabrication steps, without the need for a dedicated room, all in an argon environment. Finally, we discuss the custom-built antechamber attached to the back of the glovebox. This antechamber allows the glovebox to interface with ultra-high vacuum equipment such as molecular-beam epitaxy and scanning tunneling microscopy.

Observation of a thermoelectric Hall plateau in the extreme quantum limit

The thermoelectric Hall effect is the generation of a transverse heat current upon applying an electric field in the presence of a magnetic field. Here, we demonstrate that the thermoelectric Hall conductivity αxy in the three-dimensional Dirac semimetal ZrTe5 acquires a robust plateau in the extreme quantum limit of magnetic field. The plateau value is independent of the field strength, disorder strength, carrier concentration, or carrier sign. We explain this plateau theoretically and show that it is a unique signature of three-dimensional Dirac or Weyl electrons in the extreme quantum limit. We further find that other thermoelectric coefficients, such as the thermopower and Nernst coefficient, are greatly enhanced over their zero-field values even at relatively low fields.

Weak-field induced nonmagnetic state in a Co-based honeycomb

Layered honeycomb magnets are of interest as potential realizations of the Kitaev quantum spin liquid (KQSL), a quantum state with long-range spin entanglement and an exactly solvable Hamiltonian. Conventional magnetically ordered states are present for all currently known candidate materials, however, because non-Kitaev terms in the Hamiltonians obscure the Kitaev physics. Current experimental studies of the KQSL are focused on 4d or 5d transition metal-based honeycombs, in which strong spin-orbit coupling can be expected, yielding Kitaev interaction that dominates in an applied magnetic field. In contrast, for 3d-based layered honeycomb magnets, spin-orbit coupling is weak, and thus, Kitaev physics should be substantially less accessible. Here, we report our studies on BaCo₂(AsO₄)₂, for which we find that the magnetic order associated with the non-Kitaev interactions can be fully suppressed by a relatively low magnetic field, yielding a nonmagnetic material and implying the presence of strong magnetic frustration and weak non-Kitaev interactions.

Nearly quantized conductance plateau of vortex zero mode in an iron-based superconductor

Majorana zero modes (MZMs) are spatially localized, zero-energy fractional quasiparticles with non-Abelian braiding statistics that hold promise for topological quantum computing. Owing to the particle-antiparticle equivalence, MZMs exhibit quantized conductance at low temperature. By using variable-tunnel-coupled scanning tunneling spectroscopy, we studied tunneling conductance of vortex bound states on FeTe_0.55Se_0.45 superconductors. We report observations of conductance plateaus as a function of tunnel coupling for zero-energy vortex bound states with values close to or even reaching the 2e ²/h quantum conductance (where e is the electron charge and h is Planck's constant). By contrast, no plateaus were observed on either finite energy vortex bound states or in the continuum of electronic states outside the superconducting gap. This behavior of the zero-mode conductance supports the existence of MZMs in FeTe_0.55Se_0.45.

Evidence for Helical Hinge Zero Modes in an Fe-Based Superconductor

Combining topology and superconductivity provides a powerful tool for investigating fundamental physics as well as a route to fault-tolerant quantum computing. There is mounting evidence that the Fe-based superconductor FeTe_0.55Se_0.45 (FTS) may also be topologically nontrivial. Should the superconducting order be s^±, then FTS could be a higher order topological superconductor with helical hinge zero modes (HHZMs). To test the presence of these modes, we have fabricated normal-metal/superconductor junctions on different surfaces via 2D atomic crystal heterostructures. As expected, junctions in contact with the hinge reveal a sharp zero bias anomaly that is absent when tunneling purely into the c-axis. Additionally, the shape and suppression with temperature are consistent with highly coherent modes along the hinge and are incongruous with other origins of zero bias anomalies. Additional measurements with soft-point contacts in bulk samples with various Fe interstitial contents demonstrate the intrinsic nature of the observed mode. Thus, we provide evidence that FTS is indeed a higher order topological superconductor.

Magnetic properties of the BaNi2(As1-x V x )2O8 honeycomb system

The Kitaev model for magnetic interactions on a honeycomb lattice, which underlies the exotic quantum spin liquid (QSL) state in such systems, has long been established and experimentally confirmed. Current studies on Kitaev QSLs have focused on heavy-metal-based Mott insulators where strong spin-orbit coupling (SOC) leads to bond-dependent spin anisotropy. Here we examine a 3d transition-metal-based honeycomb lattice material BaNi₂(As_1-x V _x )₂O₈, where the SOC is weak but spin exchange coupling is strongly frustrated due to the crystal field. We present an investigation of the crystal structure and magnetization of this series of Ni-based honeycomb materials, providing an alternative perspective in the search for the QSL in 3d-element-based honeycomb systems.

Sign-Reversing Hall Effect in Atomically Thin High-Temperature Bi_{2.1}Sr_{1.9}CaCu_{2.0}O_{8+δ} Superconductors

We developed novel techniques to fabricate atomically thin Bi_{2.1}Sr_{1.9}CaCu_{2.0}O_{8+δ} van der Waals heterostructures down to two unit cells while maintaining a transition temperature T_{c} close to the bulk, and carry out magnetotransport measurements on these van der Waals devices. We find a double sign change of the Hall resistance R_{xy} as in the bulk system, spanning both below and above T_{c}. Further, we observe a drastic enlargement of the region of sign reversal in the temperature-magnetic field phase diagram with decreasing thickness of the device. We obtain quantitative agreement between experimental R_{xy}(T,B) and the predictions of the vortex dynamics-based description of Hall effect in high-temperature superconductors both above and below T_{c}.

A New Magnetic Topological Quantum Material Candidate by Design

Magnetism, when combined with an unconventional electronic band structure, can give rise to forefront electronic properties such as the quantum anomalous Hall effect, axion electrodynamics, and Majorana fermions. Here we report the characterization of high-quality crystals of EuSn₂P₂, a new quantum material specifically designed to engender unconventional electronic states plus magnetism. EuSn₂P₂ has a layered, Bi₂Te₃-type structure. Ferromagnetic interactions dominate the Curie-Weiss susceptibility, but a transition to antiferromagnetic ordering occurs near 30 K. Neutron diffraction reveals that this is due to two-dimensional ferromagnetic spin alignment within individual Eu layers and antiferromagnetic alignment between layers-this magnetic state surrounds the Sn-P layers at low temperatures. The bulk electrical resistivity is sensitive to the magnetism. Electronic structure calculations reveal that EuSn₂P₂ might be a strong topological insulator, which can be a new magnetic topological quantum material (MTQM) candidate. The calculations show that surface states should be present, and they are indeed observed by angle-resolved photoelectron spectroscopy (ARPES) measurements.

Directly visualizing the sign change of d-wave superconducting gap in Bi2Sr2CaCu2O8+δ by phase-referenced quasiparticle interference

The superconducting state is formed by the condensation of Cooper pairs and protected by the superconducting gap. The pairing interaction between the two electrons of a Cooper pair determines the gap function. Thus, it is pivotal to detect the gap structure for understanding the mechanism of superconductivity. In cuprate superconductors, it has been well established that the gap may have a d-wave function. This gap function has an alternative sign change in the momentum space. It is however hard to visualize this sign change. Here we report the measurements of scanning tunneling spectroscopy in Bi2Sr2CaCu2O8+δ and conduct the analysis of phase-referenced quasiparticle interference (QPI). We see the seven basic scattering vectors that connect the octet ends of the banana-shaped contour of Fermi surface. The phase-referenced QPI clearly visualizes the sign change of the d-wave gap. Our results illustrate an effective way for determining the sign change of unconventional superconductors.

A polymorphic MYC response element in KBTBD11 influences colorectal cancer risk, especially in interaction with an MYC-regulated SNP rs6983267

Background

MYC is a well-established cancer driver gene regulating the expression of numerous genes, indicating that polymorphisms in MYC response elements could affect tumorigenesis through altering MYC regulation. We performed integrative multistage study to evaluate the effects of variants in MYC response elements and colorectal cancer (CRC) risk.

Patients and methods

We systematically integrated ChIP-Seq, DNase-Seq and transcription factor motif data to screen variants with potential ability to affect the MYC binding affinity. Then, we conducted a two-stage case-control study, totally consisting of 4830 CRC cases and 4759 controls in Chinese population to identify risk polymorphisms and interactions. The effects of risk variants were confirmed by functional assays in CRC LoVo, SW480 and HCT15 cells.

Results

We identified a novel polymorphism rs11777210 in KBTBD11 significantly associated with CRC susceptibility (P = 2.43 × 10-12). Notably, we observed a significant interaction between rs11777210 and MYC nearby rs6983267 (P-multi = 0.003, P-add = 0.005), subjects carrying rs6983267 GG and rs11777210 CC genotypes showing higher susceptibility to CRC (2.83-fold) than those carrying rs6983267 TT and rs11777210 TT genotypes. We further demonstrated that rs6983267 T > G increased MYC expression, and MYC bound to and negatively regulated KBTBD11 expression when the rs11777210 C risk allele was present. KBTBD11 was downregulated in tumor tissues, and KBTBD11 knockdown promoted cell proliferation and inhibited cell apoptosis.

Conclusion

The rs11777210 is a potential predictive biomarker of CRC susceptibility, and KBTBD11 functions as a putative tumor suppressor in tumorigenesis. Our study highlighted the high CRC risk of people carrying rs6983267 G and rs11777210 C alleles, and provided possible biological mechanism of the interaction.

Charge-stripe crystal phase in an insulating cuprate

High-temperature (high-T_c) superconductivity in cuprates arises from carrier doping of an antiferromagnetic Mott insulator. This carrier doping leads to the formation of electronic liquid-crystal phases¹. The insulating charge-stripe crystal phase is predicted to form when a small density of holes is doped into the charge-transfer insulator state^1-3, but this phase is yet to be observed experimentally. Here, we use surface annealing to extend the accessible doping range in Bi-based cuprates and realize the lightly doped charge-transfer insulating state of the cuprate Bi₂Sr₂CaCu₂O_8+x. In this insulating state with a charge transfer gap on the order of ~1 eV, our spectroscopic imaging scanning tunnelling microscopy measurements provide strong evidence for a unidirectional charge-stripe order with a commensurate 4a₀ period along the Cu-O-Cu bond. Notably, this insulating charge-stripe crystal phase develops before the onset of the pseudogap and formation of the Fermi surface. Our work provides fresh insight into the microscopic origin of electronic inhomogeneity in high-T_c cuprates.

Superconductor-Insulator Transitions in Exfoliated Bi2Sr2CaCu2O8+δ Flakes

We realize superconductor-insulator transitions (SIT) in mechanically exfoliated Bi₂Sr₂CaCu₂O_8+δ (BSCCO) flakes and address simultaneously their transport properties as well as the evolution of density of states. Back-gating via the solid ion conductor (SIC) engenders a SIT in BSCCO due to the modulation of carrier density by intercalated lithium ions. Scaling analysis indicates that the SIT follows the theoretical description of a two-dimensional quantum phase transition (2D-QPT). We further carry out tunneling spectroscopy in graphite(G)/BSCCO heterojunctions. We observe V-shaped gaps in the critical regime of the SIT. The density of states in BSCCO gets symmetrically suppressed by further going into the insulating regime. Our technique of combining solid state gating with tunneling spectroscopy can be easily applied to the study of other two-dimensional materials.

Evidence for Majorana bound states in an iron-based superconductor

The search for Majorana bound states (MBSs) has been fueled by the prospect of using their non-Abelian statistics for robust quantum computation. Two-dimensional superconducting topological materials have been predicted to host MBSs as zero-energy modes in vortex cores. By using scanning tunneling spectroscopy on the superconducting Dirac surface state of the iron-based superconductor FeTe_0.55Se_0.45, we observed a sharp zero-bias peak inside a vortex core that does not split when moving away from the vortex center. The evolution of the peak under varying magnetic field, temperature, and tunneling barrier is consistent with the tunneling to a nearly pure MBS, separated from nontopological bound states. This observation offers a potential platform for realizing and manipulating MBSs at a relatively high temperature.