1,227 research outputs found
Itinerant quantum critical point with frustration and non-Fermi-liquid
Employing the self-learning quantum Monte Carlo algorithm, we investigate the
frustrated transverse-field triangle-lattice Ising model coupled to a Fermi
surface. Without fermions, the spin degrees of freedom undergoes a second-order
quantum phase transition between paramagnetic and clock-ordered phases. This
quantum critical point (QCP) has an emergent U(1) symmetry and thus belongs to
the (2+1)D XY universality class. In the presence of fermions, spin
fluctuations introduce effective interactions among fermions and distort the
bare Fermi surface towards an interacting one with hot spots and Fermi pockets.
Near the QCP, non-Fermi-liquid behavior are observed at the hot spots, and the
QCP is rendered into a different universality with Hertz-Millis type exponents.
The detailed properties of this QCP and possibly related experimental systems
are also discussed.Comment: 9 pages, 8 figure
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A Novel Aptamer LL4A Specifically Targets Vemurafenib-Resistant Melanoma through Binding to the CD63 Protein.
Melanoma is a highly aggressive tumor with a poor prognosis, and half of all melanoma patients harbor BRAF mutations. A BRAF inhibitor, vemurafenib (PLX4032), has been approved by the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) to treat advanced melanoma patients with BRAFV600E mutation. However, the efficacy of vemurafenib is impeded by adaptive resistance in almost all patients. In this study, using a cell-based SELEX (systematic evolution of ligands by exponential enrichment) strategy, we obtained a DNA aptamer (named LL4) with high affinity and specificity against vemurafenib-resistant melanoma cells. Optimized truncated form (LL4A) specifically binds to vemurafenib-resistant melanoma cells with dissociation constants in the nanomolar range and with excellent stability and low toxicity. Meanwhile, fluorescence imaging confirmed that LL4A significantly accumulated in tumors formed by vemurafenib-resistant melanoma cells, but not in control tumors formed by their corresponding parental cells in vivo. Further, a transmembrane protein CD63 was identified as the binding target of aptamer LL4A using a pull-down assay combined with the liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. CD63 formed a supramolecular complex with TIMP1 and β1-integrin, activated the nuclear factor кB (NF-кB) and mitogen-activated protein kinase (MAPK) signaling pathways, and contributed to vemurafenib resistance. Potentially, the aptamer LL4A may be used diagnostically and therapeutically in humans to treat targeted vemurafenib-resistant melanoma
Magnetic quantum phase transition in a metallic Kondo heterostructure
We consider a two-dimensional quantum spin system described by a Heisenberg
model that is embedded in a three-dimensional metal. The two systems couple via
an antiferromagnetic Kondo interaction. In such a setup, the ground state
generically remains metallic down to the lowest temperatures and allows us to
study magnetic quantum phase transitions in metallic environments. From the
symmetry point of view, translation symmetry is present in two out of three
lattice directions such that crystal momentum is only partially conserved.
Importantly, the construction provides a route to study, with
negative-sign-free auxiliary-field quantum Monte Carlo methods, the physics of
local moments in metallic environments. Our large-scale numerical simulations
show that as a function of the Kondo coupling, the system has two metallic
phases. In the limit of strong Kondo coupling, a paramagnetic heavy-fermion
phase emerges. Here, the spin degree of freedom is screened by means of the
formation of a composite quasiparticle that participates in the Luttinger
count. At weak Kondo coupling, magnetic order is present. This phase is
characterized by Landau-damped Goldstone modes. Furthermore, the aforementioned
composite quasiparticle remains intact across the quantum phase transition.Comment: 19 pages, 15 figure
Marginal Fermi liquid at magnetic quantum criticality from dimensional confinement
Metallic quantum criticality is frequently discussed as a source for
non-Fermi liquid behavior, but controlled theoretical treatments are scarce.
Here we identify and study a novel magnetic quantum critical point in a
two-dimensional antiferromagnet coupled to a three-dimensional environment of
conduction electrons. Using sign-problem-free quantum Monte Carlo simulations
and an effective field-theory analysis, we demonstrate that the quantum
critical point is characterized by marginal Fermi liquid behavior. In
particular, we compute the electrical resistivity for transport across the
magnetic layer, which is shown to display a linear temperature dependence at
criticality. Experimental realizations in Kondo heterostructures are discussed.Comment: 6 pages, 4 figure; Supplement: 12 pages, 12 figure
Many versus one: the disorder operator and entanglement entropy in fermionic quantum matter
Motivated by recent development of the concept of the disorder operator and
its relation with entanglement entropy in bosonic systems, here we show the
disorder operator successfully probes many aspects of quantum entanglement in
fermionic many-body systems. From both analytical and numerical computations in
free and interacting fermion systems in 1D and 2D, we find the disorder
operator and the entanglement entropy exhibit similar universal scaling
behavior, as a function of the boundary length of the subsystem, but with
subtle yet important differences. In 1D they both follow the scaling
behavior with the coefficient determined by the Luttinger parameter for
disorder operator, and the conformal central charge for entanglement entropy.
In 2D they both show the universal scaling behavior in free and
interacting Fermi liquid states, with the coefficients depending on the
geometry of the Fermi surfaces. However at a 2D quantum critical point with
non-Fermi-liquid state, extra symmetry information is needed in the design of
the disorder operator, so as to reveal the critical fluctuations as does the
entanglement entropy. Our results demonstrate the fermion disorder operator can
be used to probe quantum many-body entanglement related to global symmetry, and
provides new tools to explore the still largely unknown territory of highly
entangled fermion quantum matter in 2 or higher dimensions.Comment: 13 pages, 7 figures with 8 pages supplemental materia
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(QCP). Here we study, by
means of large-scale quantum Monte Carlo simulation, the scaling behavior of
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.Comment: 16 pages, 18 figure
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