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Strongly interacting topological matter 1 exhibits fundamentally new phenomena with potential applications in quantum information technology 2,3 . Emblematic instances are fractional quantum Hall (FQH) states 4 , in which the interplay of a magnetic field and strong interactions gives rise to fractionally charged quasi-particles, long-ranged entanglement and anyonic exchange statistics. Progress in engineering synthetic magnetic fields 5-21 has raised the hope to create these exotic states in controlled quantum systems. However, except for a recent Laughlin state of light 22 , preparing FQH states in engineered systems remains elusive. Here we realize a FQH state with ultracold atoms in an optical lattice. The state is a lattice version of a bosonic ν = 1/2 Laughlin state 4,23 with two particles on 16 sites. This minimal system already captures many hallmark features of Laughlin-type FQH states 24-28 : we observe a suppression of two-body interactions, we find a distinctive vortex structure in the density correlations and we measure a fractional Hall conductivity of σ H /σ 0  = 0.6(2) by means of the bulk response to a magnetic perturbation. Furthermore, by tuning the magnetic field, we map out the transition point between the normal and the FQH regime through a spectroscopic investigation of the many-body gap. Our work provides a starting point for exploring highly entangled topological matter with ultracold atoms 29-33 ., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Quantum Hall (QH) edge channels propagating along the periphery of two-dimensional (2D) electron gases under perpendicular magnetic field are a major paradigm in physics. However, groundbreaking experiments that could use them in graphene are hampered by the conjecture that QH edge channels undergo a reconstruction with additional nontopological upstream modes. By performing scanning tunneling spectroscopy up to the edge of a graphene flake on hexagonal boron nitride, we show that QH edge channels are confined to a few magnetic lengths at the crystal edges. This implies that they are ideal 1D chiral channels defined by boundary conditions of vanishing electronic wave functions at the crystal edges, hence free of electrostatic reconstruction. We further evidence a uniform charge carrier density at the edges, incompatible with the existence of upstream modes. This work has profound implications for electron and heat transport experiments in graphene-based systems and other 2D crystalline materials.

We show that a chiral spin liquid spontaneously emerges in partially amorphous, polycrystalline, or ion-irradiated Kitaev materials. In these systems, time-reversal symmetry is broken spontaneously due to a nonzero density of plaquettes with an odd number of edges n_{odd}. This mechanism opens a sizable gap, at small n_{odd} compatible with that of typical amorphous materials and polycrystals, and which can alternatively be induced by ion irradiation. We find that the gap is proportional to n_{odd}, saturating at n_{odd}∼40%. Using exact diagonalization, we find that the chiral spin liquid is approximately as stable to Heisenberg interactions as Kitaev's honeycomb spin-liquid model. Our results open up a significant number of noncrystalline systems where chiral spin liquids can emerge without external magnetic fields.

Abstarct: When electrons populate a flat band their kinetic energy becomes negligible, forcing them to organize in exotic many-body states to minimize their Coulomb energy 1-5 . The zeroth Landau level of graphene under a magnetic field is a particularly interesting strongly interacting flat band because interelectron interactions are predicted to induce a rich variety of broken-symmetry states with distinct topological and lattice-scale orders 6-11 . Evidence for these states stems mostly from indirect transport experiments that suggest that broken-symmetry states are tunable by boosting the Zeeman energy 12 or by dielectric screening of the Coulomb interaction 13 . However, confirming the existence of these ground states requires a direct visualization of their lattice-scale orders 14 . Here we image three distinct broken-symmetry phases in graphene using scanning tunnelling spectroscopy. We explore the phase diagram by tuning the screening of the Coulomb interaction by a low- or high-dielectric-constant environment, and with a magnetic field. In the unscreened case, we find a Kekulé bond order, consistent with observations of an insulating state undergoing a magnetic-field driven Kosterlitz-Thouless transition 15,16 . Under dielectric screening, a sublattice-unpolarized ground state 13 emerges at low magnetic fields, and transits to a charge-density-wave order with partial sublattice polarization at higher magnetic fields. The Kekulé and charge-density-wave orders furthermore coexist with additional, secondary lattice-scale orders that enrich the phase diagram beyond current theory predictions 6-10 . This screening-induced tunability of broken-symmetry orders may prove valuable to uncover correlated phases of matter in other quantum materials., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Combinatorial methods enable the synthesis of chemical libraries on scales of millions to billions of compounds, but the ability to efficiently screen and sequence such large libraries has remained a major bottleneck for molecular discovery. We developed a novel technology for screening and sequencing libraries of synthetic molecules of up to a billion compounds in size. This platform utilizes the fiber-optic array scanning technology (FAST) to screen bead-based libraries of synthetic compounds at a rate of 5 million compounds per minute (∼83 000 Hz). This ultra-high-throughput screening platform has been used to screen libraries of synthetic "self-readable" non-natural polymers that can be sequenced at the femtomole scale by chemical fragmentation and high-resolution mass spectrometry. The versatility and throughput of the platform were demonstrated by screening two libraries of non-natural polyamide polymers with sizes of 1.77M and 1B compounds against the protein targets K-Ras, asialoglycoprotein receptor 1 (ASGPR), IL-6, IL-6 receptor (IL-6R), and TNFα. Hits with low nanomolar binding affinities were found against all targets, including competitive inhibitors of K-Ras binding to Raf and functionally active uptake ligands for ASGPR facilitating intracellular delivery of a nonglycan ligand., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Many graphene moiré superlattices host narrow bands with nonzero valley Chern numbers. We provide analytical and numerical evidence for a robust spin and/or valley polarized insulator at total integer band filling in nearly flat bands of several different moiré materials. In the limit of a perfectly flat band, we present analytical arguments in favor of the ferromagnetic state substantiated by numerical calculations. Further, we numerically evaluate its stability for a finite bandwidth. We provide exact diagonalization results for models appropriate for ABC trilayer graphene aligned with hBN, twisted double bilayer graphene, and twisted bilayer graphene aligned with hBN. We also provide DMRG results for a honeycomb lattice with a quasiflat band and nonzero Chern number, which extend our results to larger system sizes. We find a maximally spin and valley polarized insulator at all integer fillings when the band is sufficiently flat. We also show that interactions may induce effective dispersive terms strong enough to destabilize this state. These results still hold in the case of zero valley Chern number (for example, trivial side of TLG/hBN). We give an intuitive picture based on extended Wannier orbitals, and emphasize the role of the quantum geometry of the band, whose microscopic details may enhance or weaken ferromagnetism in moiré materials.

The robust quantization of observables in units of universal constants is a hallmark of topological phases. We show that chiral higher order topological insulators (HOTIs), bulk insulators with chiral hinge states, present two unusual features related to quantization. First, we show that circular dichroism is quantized to an integer or zero depending on the orientation of the sample. This probe locates the hinge states, and can be used to distinguish different types of chiral HOTIs. Second, we find that the average of the local Chern marker over a single surface, an observable related to the surface Hall conductivity known to be quantized in the infinite slab geometry, is nonuniversal for a finite surface. This is due to a nonuniversal contribution of the hinge states, previously unaccounted for, that distinguishes surfaces of chiral HOTIs from Chern insulators. Our findings are relevant to establish higher order topology in systems such as the axion insulator candidate EuIn_{2}As_{2}, and cold atomic realizations.

We propose a simple microscopic model to numerically investigate the stability of a two-dimensional fractional topological insulator (FTI). The simplest example of an FTI consists of two decoupled copies of a Laughlin state with opposite chiralities, or double-semion phase. We focus on bosons at half filling. We study the stability of the FTI phase upon addition of two coupling terms of different nature: an interspin interaction term, and an inversion-symmetry-breaking term that couples the copies at the single-particle level. Using exact-diagonalization and entanglement spectra, we numerically show that the FTI phase is stable against both perturbations. We compare our system to a similar bilayer fractional Chern insulator. We show evidence that the time-reversal-invariant system survives the introduction of interaction coupling on a larger scale than the time-reversal-symmetry-breaking one, stressing the importance of time-reversal symmetry in the FTI phase stability. We also discuss possible fractional phases beyond ν=1/2. [ABSTRACT FROM AUTHOR]

We report the observation of a series of Abelian and non-Abelian topological states in fractional Chern insulators (FCIs). The states appear at bosonic filling ν=k/(C+1) (k,C integers) in several lattice models, in fractionally filled bands of Chern numbers C≥1 subject to on-site Hubbard interactions. We show strong evidence that the k=1 series is Abelian while the k>1 series is non-Abelian. The energy spectrum at both ground-state filling and upon the addition of quasiholes shows a low-lying manifold of states whose total degeneracy and counting matches, at the appropriate size, that of the fractional quantum Hall (FQH) SU(C) (color) singlet k-clustered states (including Halperin, non-Abelian spin singlet states and their generalizations). The ground-state momenta are correctly predicted by the FQH to FCI lattice folding. However, the counting of FCI states also matches that of a spinless FQH series, preventing a clear identification just from the energy spectrum. The entanglement spectrum lends support to the identification of our states as SU(C) color singlets, but offers anomalies in the counting for C > 1, possibly related to dislocations that call for the development of alternative counting rules of these topological states. [ABSTRACT FROM AUTHOR]

We report the first numerical observation of composite fermion (CF) states in fractional Chern insulators (FCI) using exact diagonalization. The ruby lattice Chern insulator model for both fermions and bosons exhibits a clear signature of CF states at filling factors 2/5 and 3/7 (2/3 and 3/4 for bosons). The topological properties of these states are studied through several approaches. Quasihole and quasielectron excitations in FCI display similar features as their fractional quantum hall (FQH) counterparts. The entanglement spectrum of FCI ground states shows an identical fingerprint to its FQH partner. We show that the correspondence between FCI and FQH obeys the emergent symmetry already established, proving the validity of this approach beyond the clustered states. We investigate other Chern insulator models and find similar signatures of CF states. However, some of these systems exhibit strong finite size effects. [ABSTRACT FROM AUTHOR]

The clinical efficacy of epidermal growth factor receptor (EGFR) kinase inhibitors is limited by the development of drug resistance. The irreversible EGFR kinase inhibitor WZ4002 is effective against the most common mechanism of drug resistance mediated by the EGFR T790M mutation. Here, we show, in multiple complementary models, that resistance to WZ4002 develops through aberrant activation of extracellular signal-regulated kinase (ERK) signaling caused by either an amplification of mitogen-activated protein kinase 1 (MAPK1) or by downregulation of negative regulators of ERK signaling. Inhibition of MAP-ERK kinase (MEK) or ERK restores sensitivity to WZ4002 and prevents the emergence of drug resistance. We further identify MAPK1 amplification in an erlotinib-resistant EGFR-mutant non-small cell lung carcinoma patient. In addition, the WZ4002-resistant MAPK1-amplified cells also show an increase both in EGFR internalization and a decrease in sensitivity to cytotoxic chemotherapy. Our findings provide insights into mechanisms of drug resistance to EGFR kinase inhibitors and highlight rational combination therapies that should be evaluated in clinical trials.

Moiré superlattices have emerged as an excellent platform for investigating a plethora of exotic quantum states in condensed matter physics. Recent advancements have unveiled abundant discoveries in two-dimensional moiré superlattices. In this paper, we will present a review of the recent progresses in superconductivity and topological physics within graphene and transition metal dichalcogenides-based moiré superlattices. Additionally, we outline future potential challenges and desirable efforts for discovering, understanding, and controlling these novel states in two-dimensional moiré superlattices. [ABSTRACT FROM AUTHOR]

The structure and expression of 14-3-3 sigma(sigma) was analysed in squamous carcinomas (SCC) of the vulva and in the vulval pre-malignant lesion vulval intraepithelial neoplasia (VIN). Sequence analysis of the sigma coding region did not detect mutations in any case of SCC or VIN III and loss of heterozygosity (LOH) occurred in only 2 out of 27 informative cases. In contrast to the absence of genetic change, methylation-specific PCR (MSP) analysis revealed dense CpG methylation within the sigma gene in approximately 60% of cases of vulval SCC, but methylation was not detected in matched, normal epithelial tissue. Methylation was associated in all cases with reduced or absent expression of sigma mRNA. There was no correlation between sigma methylation and HPV or p53 status. Analysis of pre-malignant vulval intraepithelial neoplasia (VIN) revealed that sigma methylation was detectable early in neoplastic development. Co-incident methylation, accompanied by loss of expression, of sigma and p16INK4a was commonly detected in both SCC and VIN III, suggesting that epigenetic silencing of these two genes is an early and important event in vulval neoplasia.

The structure and expression of the human Rad53 homologue Chk2 was analysed in breast cancer. The previously described silent polymorphism at nucleotide 252 in codon 84 (GAA>GAG) was observed in 5/141 cases. Somatic Chk2 coding mutations were detected in 7/141 cases, these occurring in 4/18 BRCA1-associated breast cancers, 1/78 sporadic breast cancers and 2/25 typical medullary carcinomas. Each of the BRCA1-associated cancers with Chk2 mutations also contained mutations in p53, whereas the single sporadic cancer with Chk2 mutation was wild-type for p53. Expression of Chk2 was ubiquitously detected in normal ductal epithelium of the breast, but there was loss of expression in a significant proportion of breast carcinomas, and this occurred in cancers both with and without p53 mutation. A CpG island was identified 5' of the Chk2 transcriptional start site, but there was no evidence of cytosine methylation in any of the cancers with down-regulated Chk2 expression. Analysis of the germ-line of 45 individuals with hereditary or early onset breast cancer revealed wild-type Chk2 sequence in all cases. Thus, despite the rarity of somatic mutations in Chk2 in sporadic breast carcinomas, our results nevertheless reveal that concomitant loss of function in Chk2 (via down-regulation of expression) and p53 (via mutation) occurs in a proportion of sporadic cases. However, consistent with other studies, we show that germ-line mutations in Chk2 are unlikely to account for a significant proportion of non BRCA1-, non BRCA2-associated hereditary breast cancers.

Physics is living an era of unprecedented cross-fertilization among the different areas of science. In this perspective review, we discuss the manifold impact that state-of-the-art cold and ultracold-atomic platforms can have in fundamental and applied science through the development of platforms for quantum simulation, computation, metrology and sensing. We illustrate how the engineering of table-top experiments with atom technologies is engendering applications to understand problems in condensed matter and fundamental physics, cosmology and astrophysics, unveil foundational aspects of quantum mechanics, and advance quantum chemistry and the emerging field of quantum biology. In this journey, we take the perspective of two main approaches, i.e., creating quantum analogues and building quantum simulators, highlighting that independently of the ultimate goal of a universal quantum computer to be met, the remarkable transformative effects of these achievements remain unchanged. We wish to convey three main messages. First, this atom-based quantum technology enterprise is signing a new era in the way quantum technologies are used for fundamental science, even beyond the advancement of knowledge, which is characterised by truly cross-disciplinary research, extended interplay between theoretical and experimental thinking, and intersectoral approach. Second, quantum many-body physics is unavoidably taking center stage in frontier's science. Third, quantum science and technology progress will have capillary impact on society, meaning this effect is not confined to isolated or highly specialized areas of knowledge, but is expected to reach and have a pervasive influence on a broad range of society aspects: while this happens, the adoption of a responsible research and innovation approach to quantum technologies is mandatory, to accompany citizens in building awareness and future scaffolding. Following on all the above reflections, this perspective review is thus aimed at scientists active or interested in interdisciplinary research, providing the reader with an overview of the current status of these wide fields of research where cold and ultracold-atomic platforms play a vital role in their description and simulation. [ABSTRACT FROM AUTHOR]

The fractional quantum anomalous Hall effect (FQAHE), the analogue of the fractional quantum Hall effect1 at zero magnetic field, is predicted to exist in topological flat bands under spontaneous time-reversal-symmetry breaking2–6. The demonstration of FQAHE could lead to non-Abelian anyons that form the basis of topological quantum computation7–9. So far, FQAHE has been observed only in twisted MoTe2 at a moiré filling factor v > 1/2 (refs. 10–13). Graphene-based moiré superlattices are believed to host FQAHE with the potential advantage of superior material quality and higher electron mobility. Here we report the observation of integer and fractional QAH effects in a rhombohedral pentalayer graphene–hBN moiré superlattice. At zero magnetic field, we observed plateaus of quantized Hall resistance R x y = h v e 2 at v = 1, 2/3, 3/5, 4/7, 4/9, 3/7 and 2/5 of the moiré superlattice, respectively, accompanied by clear dips in the longitudinal resistance Rxx. Rxy equals 2 h e 2 at v = 1/2 and varies linearly with v, similar to the composite Fermi liquid in the half-filled lowest Landau level at high magnetic fields14–16. By tuning the gate-displacement field D and v, we observed phase transitions from composite Fermi liquid and FQAH states to other correlated electron states. Our system provides an ideal platform for exploring charge fractionalization and (non-Abelian) anyonic braiding at zero magnetic field7–9,17–19, especially considering a lateral junction between FQAHE and superconducting regions in the same device20–22.Integer and fractional quantum anomalous Hall effects in a rhombohedral pentalayer graphene–hBN moiré superlattice are observed, providing an ideal platform for exploring charge fractionalization and (non-Abelian) anyonic braiding at zero magnetic field. [ABSTRACT FROM AUTHOR]

We develop a strong coupling approach towards quantum magnetism in Mott insulators for Wannier-obstructed bands. Despite the lack of Wannier orbitals, electrons can still singly occupy a set of exponentially localized but nonorthogonal orbitals to minimize the repulsive interaction energy. We develop a systematic method to establish an effective spin model from the electron Hamiltonian using a diagrammatic approach. The nonorthogonality of the Mott basis gives rise to multiple new channels of spin-exchange (or permutation) interactions beyond Hartree–Fock and superexchange terms. We apply this approach to a Kagome lattice model of interacting electrons in Wannier-obstructed bands (including both Chern bands and fragile topological bands). Due to the orbital nonorthogonality, as parameterized by the nearest-neighbor orbital overlap g, this model exhibits stable ferromagnetism up to a finite bandwidth W ∼ U g , where U is the interaction strength. This provides an explanation for the experimentally observed robust ferromagnetism in Wannier-obstructed bands. The effective spin model constructed through our approach also opens up the possibility for frustrated quantum magnetism around the ferromagnet-antiferromagnet crossover in Wannier-obstructed bands. [ABSTRACT FROM AUTHOR]

The material realization of charge-4e/6e superconductivity (SC) is a big challenge. Here, we propose to realize charge-4e SC in maximally-twisted homobilayers, such as 45∘-twisted bilayer cuprates and 30∘-twisted bilayer graphene, referred to as twist-bilayer quasicrystals (TB-QC). When each monolayer hosts a pairing state with the largest pairing angular momentum, previous studies have found that the second-order interlayer Josephson coupling would drive chiral topological SC (TSC) in the TB-QC. Here we propose that, above the Tc of the chiral TSC, either charge-4e SC or chiral metal can arise as vestigial phases, depending on the ordering of the total- and relative-pairing-phase fields of the two layers. Based on a thorough symmetry analysis to get the low-energy effective Hamiltonian, we conduct a combined renormalization-group and Monte-Carlo study and obtain the phase diagram, which includes the charge-4e SC and chiral metal phases. Liu et al. theoretically study maximally-twisted homo-bilayers, such as 45∘-twisted bilayer cuprates and 30∘-twisted bilayer graphene. Through renormalization group and Monte-Carlo calculations, the authors reveal the presence of charge-4e superconductivity and chiral-metal phases in the phase diagram. [ABSTRACT FROM AUTHOR]

The interplay between spontaneous symmetry breaking and topology can result in exotic quantum states of matter. A celebrated example is the quantum anomalous Hall (QAH) state, which exhibits an integer quantum Hall effect at zero magnetic field owing to intrinsic ferromagnetism1–3. In the presence of strong electron–electron interactions, fractional QAH (FQAH) states at zero magnetic field can emerge4–8. These states could host fractional excitations, including non-Abelian anyons—crucial building blocks for topological quantum computation9. Here we report experimental signatures of FQAH states in a twisted molybdenum ditelluride (MoTe2) bilayer. Magnetic circular dichroism measurements reveal robust ferromagnetic states at fractionally hole-filled moiré minibands. Using trion photoluminescence as a sensor10, we obtain a Landau fan diagram showing linear shifts in carrier densities corresponding to filling factor v = −2/3 and v = −3/5 ferromagnetic states with applied magnetic field. These shifts match the Streda formula dispersion of FQAH states with fractionally quantized Hall conductance of σ x y = − 2 3 e 2 h and σ x y = − 3 5 e 2 h , respectively. Moreover, the v = −1 state exhibits a dispersion corresponding to Chern number −1, consistent with the predicted QAH state11–14. In comparison, several non-ferromagnetic states on the electron-doping side do not disperse, that is, they are trivial correlated insulators. The observed topological states can be electrically driven into topologically trivial states. Our findings provide evidence of the long-sought FQAH states, demonstrating MoTe2 moiré superlattices as a platform for exploring fractional excitations.Signatures of fractional quantum anomalous Hall states at zero magnetic field are observed in a fractionally filled moiré superlattice in a molybdenum ditelluride twisted bilayer. [ABSTRACT FROM AUTHOR]

Chern insulators, which are the lattice analogues of the quantum Hall states, can potentially manifest high-temperature topological orders at zero magnetic field to enable next-generation topological quantum devices1–3. Until now, integer Chern insulators have been experimentally demonstrated in several systems at zero magnetic field3–8, whereas fractional Chern insulators have been reported in only graphene-based systems under a finite magnetic field9,10. The emergence of semiconductor moiré materials11, which support tunable topological flat bands12,13, provides an opportunity to realize fractional Chern insulators13–16. Here we report thermodynamic evidence of both integer and fractional Chern insulators at zero magnetic field in small-angle twisted bilayer MoTe2 by combining the local electronic compressibility and magneto-optical measurements. At hole filling factor ν = 1 and 2/3, the system is incompressible and spontaneously breaks time-reversal symmetry. We show that they are integer and fractional Chern insulators, respectively, from the dispersion of the state in the filling factor with an applied magnetic field. We further demonstrate electric-field-tuned topological phase transitions involving the Chern insulators. Our findings pave the way for the demonstration of quantized fractional Hall conductance and anyonic excitation and braiding17 in semiconductor moiré materials.Thermodynamic evidence of both integer and fractional Chern insulators at zero magnetic field is reported in small-angle twisted bilayer MoTe2 by combining the local electronic compressibility and magneto-optical measurements. [ABSTRACT FROM AUTHOR]

In non-interacting systems, bands from non-trivial topology emerge strictly at half-filling and exhibit either the quantum anomalous Hall or spin Hall effects. Here we show using determinantal quantum Monte Carlo and an exactly solvable strongly interacting model that these topological states now shift to quarter filling. A topological Mott insulator is the underlying cause. The peak in the spin susceptibility is consistent with a possible ferromagnetic state at T = 0. The onset of such magnetism would convert the quantum spin Hall to a quantum anomalous Hall effect. While such a symmetry-broken phase typically is accompanied by a gap, we find that the interaction strength must exceed a critical value for this to occur. Hence, we predict that topology can obtain in a gapless phase but only in the presence of interactions in dispersive bands. These results explain the recent quarter-filled quantum anomalous Hall effects seen in moiré systems. Moire bilayers support quantum spin Hall (QSH) and quantum anomalous Hall (QAH) states, but a unified explanation is missing. Mai et al. show that by including interactions in typical models, the QSH state shifts from 1/2 to 1/4 filling and gives way to the QAH state at low temperature. [ABSTRACT FROM AUTHOR]