Strange metallicity in the doped Hubbard model

Strange or bad metallic transport, defined by incompatibility with the conventional quasiparticle picture, is a theme common to many strongly correlated materials, including high-temperature superconductors. The Hubbard model represents a minimal starting point for modeling strongly correlated systems. Here we demonstrate strange metallic transport in the doped two-dimensional Hubbard model using determinantal quantum Monte Carlo calculations. Over a wide range of doping, we observe resistivities exceeding the Mott-Ioffe-Regel limit with linear temperature dependence. The temperatures of our calculations extend to as low as 1/40 of the noninteracting bandwidth, placing our findings in the degenerate regime relevant to experimental observations of strange metallicity. Our results provide a foundation for connecting theories of strange metals to models of strongly correlated materials.

Quantum Faraday Effect in the Universe

We study the Quantum Faraday rotation starting from the photon self-energy in the presence of a constant magnetic field. The Faraday angle is calculated in the non-degenerate regime and for weak field limit. Two physical scenarios, possibly characterized by these conditions, are the recombination epoch and the jets originated in pulsars. We discuss the resonant behavior that the Faraday angle exhibits in these scenarios and investigate the possibility of detecting cosmic magnetic fields through this resonant mechanism.

Theoretical study of quantum capacitance and associated delay in armchair-edge graphene nanoribbons

This work presents a comprehensive investigation of the quantum capacitance and the associated effects on the carrier transit delay in armchair-edge graphene nanoribbons (A-GNRs) based on semi-analytical method. We emphasize on the realistic analysis of bandgap with taking edge effects into account by means of modified tight binding (TB) model. The results show that the edge effects have significant influence in defining the bandgap which is a necessary input in the accurate analyses of capacitance. The quantum capacitance is discussed in both nondegenerate (low gate voltage) and degenerate (high gate voltage) regimes. We observe that the classical capacitance limits the total gate (external) capacitance in the degenerate regime, whereas, quantum capacitance limits the external gate capacitance in the nondegenerate regime. The influence of gate capacitances on the gate delay is studied extensively to demonstrate the optimization of switching time. Moreover, the high-field behavior of a GNR is studied in the degenerate and nondegenerate regimes. We find that a smaller intrinsic capacitance appears in the channel due to high velocity carrier, which limits the quantum capacitance and thus limit the gate delay. Such detail analysis of GNRs considering a realistic model would be useful for the optimized design of GNR-based nanoelectronic devices.

Multiplicity of Solutions to a Concave–Convex Problem

This paper studies two related problems. A first one,where Δwhere Ω is a ball and 1 < q < p < r. Features described above are shown to be also exhibited by (Q) and more importantly, it is proved that minimal solutions to (Q) develop flat patterns in the degenerate regime p > 2. Finally, it should be stressed that some of the properties satisfied by (P) and (Q) hold true when Ω is a general smooth domain.

Entanglement generation in the ultra-strongly coupled Rabi model

We analyze the dynamics of the quantum Rabi model for two qubits interacting through a common bosonic field (resonator), focusing on the generation and detection of maximally entangled states. We obtain analytical results for the unitary dynamics of this system in the slow-qubit (or degenerate) regime, considering ultra-strong coupling between qubits and resonator mode, for which the rotating wave approximation (RWA) is no longer applicable. We also numerically investigate the dynamics beyond the slow-qubit condition in order to study the validity of the model in the presence of less strict conditions.

CHANNEL CONDUCTANCE OF ABA STACKING TRILAYER GRAPHENE NANORIBBON FIELD-EFFECT TRANSISTOR

In this paper, our focus is on ABA trilayer graphene nanoribbon (TGN), in which the middle layer is horizontally shifted from the top and bottom layers. The conductance model of TGN as a FET channel is presented based on Landauer formula. Besides the good reported agreement with experimental study lending support to our model, the presented model demonstrates that minimum conductivity increases dramatically by temperature. It also draws parallels between TGN and bilayer graphene nanoribbon, in which similar thermal behavior is observed. Maxwell–Boltzmann approximation is employed to form the conductance of TGN near the neutrality point. Analytical model in degenerate regime in comparison with reported data proves that TGN-based transistor will operate in degenerate regime like what we expect in conventional semiconductors. Moreover, our model confirms that in similar condition, the conductivity of TGN is less than bilayer graphene nanoribbon as reported in some experiments.