Disorder Operator and Rényi Entanglement Entropy of Symmetric Mass Generation.

The "symmetric mass generation" (SMG) quantum phase transition discovered in recent years has attracted great interest from both condensed matter and high energy theory communities. Here, interacting Dirac fermions acquire a gap without condensing any fermion bilinear mass term or any concomitant spontaneous symmetry breaking. It is hence beyond the conventional Gross-Neveu-Yukawa-Higgs paradigm. One important question we address in this Letter is whether the SMG transition corresponds to a true unitary conformal field theory. We employ the sharp diagnosis including the scaling of disorder operator and Rényi entanglement entropy in large-scale lattice model quantum Monte Carlo simulations. Our results strongly suggest that the SMG transition is indeed an unconventional quantum phase transition and it should correspond to a true (2+1)d unitary conformal field theory.

Fermion Disorder Operator at Gross-Neveu and Deconfined Quantum Criticalities.

The fermion disorder operator has been shown to reveal the entanglement information in 1D Luttinger liquids and 2D free and interacting Fermi and non-Fermi liquids emerging at quantum critical points (QCPs) [W. Jiang et al., arXiv:2209.07103]. Here we study, by means of large-scale quantum Monte Carlo simulation, the scaling behavior of the disorder operator in correlated Dirac systems. We first demonstrate the logarithmic scaling behavior of the disorder operator at the Gross-Neveu (GN) chiral Ising and Heisenberg QCPs, where consistent conformal field theory (CFT) content of the GN-QCP in its coefficient is found. Then we study a 2D monopole-free deconfined quantum critical point (DQCP) realized between a quantum-spin Hall insulator and a superconductor. Our data point to negative values of the logarithmic coefficients such that the DQCP does not correspond to a unitary CFT. Density matrix renormalization group calculations of the disorder operator on a 1D DQCP model also detect emergent continuous symmetries.

Metallic and Deconfined Quantum Criticality in Dirac Systems.

Motivated by the physics of spin-orbital liquids, we study a model of interacting Dirac fermions on a bilayer honeycomb lattice at half filling, featuring an explicit global SO(3)×U(1) symmetry. Using large-scale auxiliary-field quantum Monte Carlo (QMC) simulations, we locate two zero-temperature phase transitions as function of increasing interaction strength. First, we observe a continuous transition from the weakly interacting semimetal to a different semimetallic phase in which the SO(3) symmetry is spontaneously broken and where two out of three Dirac cones acquire a mass gap. The associated quantum critical point can be understood in terms of a Gross-Neveu-SO(3) theory. Second, we subsequently observe a transition toward an insulating phase in which the SO(3) symmetry is restored and the U(1) symmetry is spontaneously broken. While strongly first order at the mean-field level, the QMC data are consistent with a direct and continuous transition. It is thus a candidate for a new type of deconfined quantum critical point that features gapless fermionic degrees of freedom.

Itinerant quantum critical point with fermion pockets and hotspots.

Metallic quantum criticality is among the central themes in the understanding of correlated electronic systems, and converging results between analytical and numerical approaches are still under review. In this work, we develop a state-of-the-art large-scale quantum Monte Carlo simulation technique and systematically investigate the itinerant quantum critical point on a 2D square lattice with antiferromagnetic spin fluctuations at wavevector [Formula: see text]-a problem that resembles the Fermi surface setup and low-energy antiferromagnetic fluctuations in high-Tc cuprates and other critical metals, which might be relevant to their non-Fermi-liquid behaviors. System sizes of [Formula: see text] ([Formula: see text]) are comfortably accessed, and the quantum critical scaling behaviors are revealed with unprecedented high precision. We found that the antiferromagnetic spin fluctuations introduce effective interactions among fermions and the fermions in return render the bare bosonic critical point into a different universality, different from both the bare Ising universality class and the Hertz-Mills-Moriya RPA prediction. At the quantum critical point, a finite anomalous dimension [Formula: see text] is observed in the bosonic propagator, and fermions at hotspots evolve into a non-Fermi liquid. In the antiferromagnetically ordered metallic phase, fermion pockets are observed as the energy gap opens up at the hotspots. These results bridge the recent theoretical and numerical developments in metallic quantum criticality and can serve as the stepping stone toward final understanding of the 2D correlated fermions interacting with gapless critical excitations.

[Study on DNA strand breaks in workers exposed to soluble chromate].

OBJECTIVE: To explore the biological effective markers, we investigated DNA strand breaks in peripheral lymphocytes from occupational population with broad ranges of soluble chromate exposure. METHODS: We conducted a cross-sectional study in the chromate exposed workers employed at a chromate factory in a district of Jinan, Shandong Province. The studied population contained 114 workers from different processes of the chromate plants, in addition, 30 farmers in the countryside about one hundred kilometers away from the factory, without exposure to chromate were matched with the exposed subjects by age, gender and smoking status being identified as a control group. Personal information on age, chromate exposure, medical history (including acute infection and medicine usage), smoking habit and alcohol consumption was obtained by questionnaire. DNA strand breaks in lymphocytes were detected by single-cell gel electrophoresis assay (comet assay) and the DNA damaged degree was evaluated by the score weighted by comet type. The air concentration of chromate was determined by individual sampling for 8 hours per day as shift work and chromium was assayed by atomic absorption spectrometry. The chromium content in the erythrocytes from peripheral blood was determined by graphite furnace atomic absorption spectrometry. The data were analyzed by SPSS10.0 software for statistical significance. RESULTS: (1) The results showed that the score for DNA strand breaks in lymphocytes were 54.52 +/- 23.51 in the exposed group, which was significantly higher than those in the control group (24.70 +/- 11.84) (P < 0.01). (2) The degree of DNA strand breaks in lymphocytes was increased in a dose-dependent manner ranging from 0 microg/m(3) to 106.00 microg/m(3). (3) Correlation analysis showed that there was a significant positive correlation between airborne chromate concentration and the degree of DNA strand break in lymphocytes (P < 0.01). (4) By multiple regression analysis, it was found that the airborne concentrations, chromium contents in red blood cells and smoking habits were factors which might affect the degree of DNA breaks. CONCLUSION: Our findings suggest that DNA strand break in lymphocytes should be an effective biomarker for occupational chromate-exposed population and be applied in biological monitoring and health risk assessment for occupational chromate-exposed population.