Intertwined Van Hove Singularities as a Mechanism for Loop Current Order in Kagome Metals.

Recent experiments on kagome metals AV_{3}Sb_{5} (A=Cs,Rb,K) indicated spontaneous time-reversal symmetry breaking in the charge density wave state in the absence of static magnetization. The loop current order (LCO) is proposed as its cause, but a microscopic model explaining the emergence of LCO through electronic correlations has not been firmly established. We show that the coupling between van Hove singularities with distinct mirror symmetries is a key ingredient to generate LCO ground state. By constructing an effective model, we find that when multiple van Hove singularities with opposite mirror eigenvalues are close in energy, the nearest-neighbor electron repulsion favors a ground state with coexisting LCO and charge bond order. It is then demonstrated that this mechanism applies to the kagome metals AV_{3}Sb_{5}. Our findings provide an intriguing mechanism of LCO and pave the way for a deeper understanding of complex quantum phenomena in kagome systems.

Thermodynamic Characteristic for a Correlated Flat-Band System with a Quantum Anomalous Hall Ground State.

While the ground-state phase diagram of the correlated flat-band systems has been intensively investigated, the dynamic and thermodynamic properties of such lattice models are less explored, but it is the latter which is most relevant to the experimental probes (transport, quantum capacitance, and spectroscopy) of the quantum moiré materials such as twisted bilayer graphene. Here we show, by means of momentum-space quantum Monte Carlo and exact diagonalization, in chiral limit there exists a unique thermodynamic characteristic for the correlated flat-band model with interaction-driven quantum anomalous Hall (QAH) ground state, namely, the transition from the QAH insulator to the metallic state takes place at a much lower temperature compared with the zero-temperature single-particle gap generated by the long-range Coulomb interaction. Such low transition temperature comes from the proliferation of excitonic particle-hole excitations, which transfers the electrons across the gap between different topological bands to restore the broken time-reversal symmetry and gives rise to a pronounced enhancement in the charge compressibility. Future experiments, to verify such generic thermodynamic characteristics, are proposed.

Finite-Frequency Topological Maxwell Modes in Mechanical Self-Dual Kagome Lattices.

In this Letter, an elastic twisted kagome lattice at a critical twist angle, called self-dual kagome lattice, is shown to exhibit peculiar finite-frequency topological modes which emerge when certain conditions are satisfied. These states are topologically reminiscent of the zero energy (floppy) modes of Maxwell lattices, but they occur at a finite frequency in the band gap of the self-dual kagome lattice. Thus, we present a completely new class of topological modes that share similarities with both the zero frequency floppy modes in Maxwell lattices and the finite energy in-gap modes in topological insulators. We envision the presented mathematical and numerical framework to be invaluable for many technological advances pertaining to wave phenomena, such as reconfigurable waveguide designs.

Bladder paraganglioma managed with transurethral holmium laser resection: A case report.

RATIONALE: Bladder paraganglioma is characterized by headache, palpitations, hypertension, blurred vision, or sweating during voiding. Transurethral holmium laser resection is a safe and efficacious alternative method for the resection of bladder neoplasms. PATIENT CONCERNS: A 24-year-old female had a 2-year history of intermittent headaches, palpitation, and sweating during micturition. DIAGNOSIS: Physical examination revealed a rise in the patient's blood pressure to 180/90 mmHg after micturition. Laboratory examination found that the blood catecholamine metabolites were significantly increased. Abdominal ultrasound and computed tomography (CT) scan indicated a 37 mm × 31 mm paraganglioma situated at the right anterolateral wall of the bladder. A diagnosis of bladder paraganglioma was considered based on a comprehensive evaluation of the physical examination, laboratory examination, ultrasound and computerized tomography scan. INTERVENTIONS: Preoperative oral administration of a nonselective α-adrenergic receptor antagonist (phenoxybenzamine, 10 mg three times a day,) accompanied by a high-sodium diet and generous fluid intake, was initiated 2 weeks before the surgery to stabilize intraoperative hemodynamics. As the patient was newly married and nulligravid, management with transurethral resection was considered superior to open or partial cystectomy and was selected as the treatment method. OUTCOMES: Transurethral holmium resection of the bladder paraganglioma was successfully performed with blood loss less than 20 ml and well-controlled intraoperative blood pressure. The 1-year follow-up results demonstrated well-controlled symptoms. Cystoscopy and evaluation of blood catecholamine metabolites revealed no disease recurrence. LESSONS: Transurethral holmium laser resection is a good alternative approach for the resection of bladder paraganglioma, given its advantages of safety and efficacy.

Erratum: Pfaffian Formalism for Higher-Order Topological Insulators [Phys. Rev. Lett. 124, 036401 (2020)].

This corrects the article DOI: 10.1103/PhysRevLett.124.036401.

Pfaffian Formalism for Higher-Order Topological Insulators.

We generalize the Pfaffian formalism, which has been playing an important role in the study of time-reversal invariant topological insulators (TIs), to 3D chiral higher-order topological insulators (HOTIs) protected by the product of fourfold rotational symmetry C_{4} and the time-reversal symmetry T. This Pfaffian description reveals a deep and fundamental link between TIs and HOTIs, and allows important conclusions about TIs to be generalized to HOTIs. As examples, we demonstrate in the Letter how to generalize Fu-Kane's parity criterion for TIs to HOTIs, and also present a general method to efficiently compute the Z_{2} index of 3D chiral HOTIs without a global gauge.

Isolated Rare Urethral Metastasis From Primary Lung Adenocarcinoma: Case Report and Literature Review.

Background: Lung adenocarcinoma is a common respiratory malignancy, however urethral metastasis of lung adenocarcinoma has not yet been reported. This study aims to present a rare case of isolated urethral metastasis in a male patient with a history of primary lung adenocarcinoma. Case Presentation: A 69 year-old male patient was admitted complaining of dysuria and nocturia for 3 months, with a history of lung adenocarcinoma after surgery. The patient was diagnosed as benign prostatic hyperplasia (BPH) and received holmium laser enucleation of the prostate, an effective transurethral procedure to treat bladder outflow obstruction due to BPH. Four months after surgery for BPH, the patient had no improvement in symptoms and continued to complain of dysuria and perineum pain. An MRI of the pelvis indicated posterior urethral mass without any regional lymphadenopathy or other sites of lesion. Urethrocystoscopy found the mass in the membranous urethra near the verumontanum, and pathology combined with immunohistochemical staining confirmed the isolated urethral metastasis of lung adenocarcinoma. The further therapeutic regimen consisting of chemotherapy (pemetrexed combined with nedaplatin) and bevacizumab was well-tolerated, and obviously relieved the patient from dysuria and perineum pain. Conclusion: This study reported the first case of isolated rare urethral metastasis from primary lung adenocarcinoma and underlined the necessity for clinicians to remain vigilant to metastasis during follow-up of primary cancer.

Topological Protection from Random Rashba Spin-Orbit Backscattering: Ballistic Transport in a Helical Luttinger Liquid.

The combination of Rashba spin-orbit coupling and potential disorder induces a random current operator for the edge states of a 2D topological insulator. We prove that charge transport through such an edge is ballistic at any temperature, with or without Luttinger liquid interactions. The solution exploits a mapping to a spin 1/2 in a time-dependent field that preserves the projection along one randomly undulating component (integrable dynamics). Our result is exact and rules out random Rashba backscattering as a source of temperature-dependent transport, absent integrability-breaking terms.

Thermodynamics of the noninteracting Bose gas in a two-dimensional box.

Bose-Einstein condensation (BEC) of a noninteracting Bose gas of N particles in a two-dimensional box with Dirichlet boundary conditions is studied. Confirming previous work, we find that BEC occurs at finite N at low temperatures T without the occurrence of a phase transition. The conventionally-defined transition temperature T(E) for an infinite three-dimensional (3D) system is shown to correspond in a 2D system with finite N to a crossover temperature between a slow and rapid increase in the fractional boson occupation N(0)/N of the ground state with decreasing T. We further show that T(E)∼1/logN at fixed area per boson, so in the thermodynamic limit there is no significant BEC in 2D at finite T. Thus, paradoxically, BEC only occurs in 2D at finite N with no phase transition associated with it. Calculations of thermodynamic properties versus T and area A are presented, including Helmholtz free energy, entropy S, pressure p, ratio of p to the energy density U/A, heat capacity at constant volume (area) C(V) and at constant pressure C(p), isothermal compressibility κ(T) and thermal expansion coefficient α(p), obtained using both the grand-canonical ensemble (GCE) and canonical ensemble (CE) formalisms. The GCE formalism gives acceptable predictions for S, p, p/(U/A), κ(T) and α(p) at large N, T and A but fails for smaller values of these three parameters for which BEC becomes significant, whereas the CE formalism gives accurate results for all thermodynamic properties of finite systems even at low T and/or A where BEC occurs.