94 research outputs found
The conductance of correlated many-fermion systems from charge fluctuations
We put forward a relation between the static charge correlations and the
conductance of correlated many-fermion systems at zero temperature. The former
can efficiently be computed for low-dimensional systems using tensor network
approaches, while the latter is often significantly more difficult to obtain,
requiring a challenging low-frequency linear response computation or an
explicit time evolution. We put this relation to the test for quantum dot and
quantum point contact setups, where in limiting cases exact results are known.
Our study includes systems in which the one-dimensional reservoirs are
interacting.Comment: 17 pages, 7 figure
TMDs as a platform for spin liquid physics: A strong coupling study of twisted bilayer WSe
The advent of twisted moir\'e heterostructures as a playground for strongly
correlated electron physics has led to a plethora of experimental and
theoretical efforts seeking to unravel the nature of the emergent
superconducting and insulating states. Amongst these layered compositions of
two dimensional materials, transition metal dichalcogenides (TMDs) are by now
appreciated as highly-tunable platforms to simulate reinforced electronic
interactions in the presence of low-energy bands with almost negligible
bandwidth. Here, we focus on the twisted homobilayer WSe and the insulating
phase at half-filling of the flat bands reported therein. More specifically, we
explore the possibility of realizing quantum spin liquid (QSL) physics on the
basis of a strong coupling description, including up to second nearest neighbor
Heisenberg couplings and , as well as Dzyaloshinskii-Moriya (DM)
interactions. Mapping out the global phase diagram as a function of an
out-of-plane displacement field, we indeed find evidence for putative QSL
states, albeit only close to SU symmetric points. In the presence of
finite DM couplings and XXZ anisotropy, long-range order is predominantly
present, with a mix of both commensurate and incommensurate magnetic phases.Comment: 12 pages, 5 figures, supplemental material (3 pages, 1 figure
Charge density waves and their transitions in anisotropic quantum Hall systems
In recent experiments, external anisotropy has been a useful tool to tune
different phases and study their competitions. In this paper, we look at the
quantum Hall charge density wave states in the Landau level. Without
anisotropy, there are two first-order phase transitions between the Wigner
crystal, the -electron bubble phase, and the stripe phase. By adding mass
anisotropy, our analytical and numerical studies show that the -electron
bubble phase disappears and the stripe phase significantly enlarges its domain
in the phase diagram. Meanwhile, a regime of stripe crystals that may be
observed experimentally is unveiled after the bubble phase gets out. Upon
increase of the anisotropy, the energy of the phases at the transitions becomes
progressively smooth as a function of the filling. We conclude that all
first-order phase transitions are replaced by continuous phase transitions,
providing a possible realisation of continuous quantum crystalline phase
transitions.Comment: 13+3 pages, 6 figure
Superconductivity of repulsive spinless fermions with sublattice potentials
We explore unconventional superconductivity of repulsive spinless fermions on
square and honeycomb lattices with staggered sublattice potentials. The two
lattices can exhibit staggered -wave and -wave pairing, respectively, at
low doping stemming from an effective two-valley band structure. At higher
doping, in particular, the square lattice displays a much richer phase diagram
including topological superconductivity which is induced by a
qualitatively different mechanism compared to the -wave pairing. We
illuminate this from several complementary perspectives: We analytically
perform sublattice projection to analyze the effective continuum low-energy
description and we numerically calculate the binding energies for pair and
larger bound states for few-body doping near half filling. Furthermore, for
finite doping, we present phase diagrams based on extensive functional
renormalization group and and density matrix renormalization group
calculations.Comment: 6+6 page
Hue: A User-Adaptive Parser for Hybrid Logs
Log parsing, which extracts log templates from semi-structured logs and
produces structured logs, is the first and the most critical step in automated
log analysis. While existing log parsers have achieved decent results, they
suffer from two major limitations by design. First, they do not natively
support hybrid logs that consist of both single-line logs and multi-line logs
(\eg Java Exception and Hadoop Counters). Second, they fall short in
integrating domain knowledge in parsing, making it hard to identify ambiguous
tokens in logs. This paper defines a new research problem, \textit{hybrid log
parsing}, as a superset of traditional log parsing tasks, and proposes
\textit{Hue}, the first attempt for hybrid log parsing via a user-adaptive
manner. Specifically, Hue converts each log message to a sequence of special
wildcards using a key casting table and determines the log types via line
aggregating and pattern extracting. In addition, Hue can effectively utilize
user feedback via a novel merge-reject strategy, making it possible to quickly
adapt to complex and changing log templates. We evaluated Hue on three hybrid
log datasets and sixteen widely-used single-line log datasets (\ie Loghub). The
results show that Hue achieves an average grouping accuracy of 0.845 on hybrid
logs, which largely outperforms the best results (0.563 on average) obtained by
existing parsers. Hue also exhibits SOTA performance on single-line log
datasets. Furthermore, Hue has been successfully deployed in a real production
environment for daily hybrid log parsing.Comment: Accepted by ESEC/FSE 202
Itinerant Magnetism in the Triangular Lattice Hubbard Model at Half-doping: Application to Twisted Transition-Metal Dichalcogenides
We use unrestricted Hartree-Fock, density matrix renormalization group, and
variational projected entangled pair state calculations to investigate the
ground state phase diagram of the triangular lattice Hubbard model at "half
doping" relative to single occupancy, i.e. at a filling of
electrons per site. The electron-doped case has a nested Fermi surface in the
non-interacting limit, and hence a weak-coupling instability towards
density-wave orders whose wavevectors are determined by Fermi surface nesting
conditions. We find that at moderate to strong interaction strengths other
spatially-modulated orders arise, with wavevectors distinct from the nesting
vectors. In particular, we identify a series closely-competing itinerant
long-wavelength magnetically ordered states, yielding to uniform ferromagnetic
order at the largest interaction strengths. For half-hole doping and a similar
range of interaction strengths, our data indicate that magnetic orders are most
likely absent.Comment: 4+2 page
A Location-Inventory-Routing Problem in Forward and Reverse Logistics Network Design
We study a new problem of location-inventory-routing in forward and reverse logistic (LIRP-FRL) network design, which simultaneously integrates the location decisions of distribution centers (DCs), the inventory policies of opened DCs, and the vehicle routing decision in serving customers, in which new goods are produced and damaged goods are repaired by a manufacturer and then returned to the market to satisfy customers’ demands as new ones. Our objective is to minimize the total costs of manufacturing and remanufacturing goods, building DCs, shipping goods (new or recovered) between the manufacturer and opened DCs, and distributing new or recovered goods to customers and ordering and storage costs of goods. A nonlinear integer programming model is proposed to formulate the LIRP-FRL. A new tabu search (NTS) algorithm is developed to achieve near optimal solution of the problem. Numerical experiments on the benchmark instances of a simplified version of the LIRP-FRL, the capacitated location routing problem, and the randomly generated LIRP-FRL instances demonstrate the effectiveness and efficiency of the proposed NTS algorithm in problem resolution
Fractional Chern Insulator in Twisted Bilayer MoTe
A recent experiment has reported the first observation of a zero-field
fractional Chern insulator (FCI) phase in twisted bilayer MoTe moir\'e
superlattices [Nature 622, 63-68 (2023)]. The experimental observation is at an
unexpected large twist angle 3.7 and calls for a better understanding
of the FCI in real materials. In this work, we perform large-scale density
functional theory calculation for the twisted bilayer MoTe, and find that
lattice reconstruction is crucial for the appearance of an isolated flat Chern
band. The existence of the FCI state at are confirmed by exact
diagonalization. We establish phase diagrams with respect to the twist angle
and electron interaction, which reveal an optimal twist angle of
for the observation of FCI. We further demonstrate that an external electric
field can destroy the FCI state by changing band geometry and show evidence of
the FCI state in this system. Our research highlights the importance
of accurate single particle band structure in the quest for strong correlated
electronic states and provides insights into engineering fractional Chern
insulator in moir\'e superlattices
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