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A unified theory of quantum critical points beyond the conventional Landau-Ginzburg-Wilson paradigm remains unknown. According to Landau cubic criterion, phase transitions should be first-order when cubic terms of order parameters are allowed by symmetry in the Landau-Ginzburg free energy. Here, from renormalization group analysis, we show that second-order quantum phase transitions can occur at such putatively first-order transitions in interacting two-dimensional Dirac semimetals. As such type of Landau-forbidden quantum critical points are induced by gapless fermions, we call them fermion-induced quantum critical points. We further introduce a microscopic model of SU(N) fermions on the honeycomb lattice featuring a transition between Dirac semimetals and Kekule valence bond solids. Remarkably, our large-scale sign-problem-free Majorana quantum Monte Carlo simulations show convincing evidences of a fermion-induced quantum critical points for N = 2, 3, 4, 5 and 6, consistent with the renormalization group analysis. We finally discuss possible experimental realizations of the fermion-induced quantum critical points in graphene and graphene-like materials.Quantum phase transitions are governed by Landau-Ginzburg theory and the exceptions are rare. Here, Li et al. propose a type of Landau-forbidden quantum critical points induced by gapless fermions in two-dimensional Dirac semimetals.
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http://dx.doi.org/10.1038/s41467-017-00167-6 | DOI Listing |
JACC Heart Fail
February 2025
BHF Cardiovascular Research Centre, University of Glasgow, Glasgow, Scotland, United Kingdom. Electronic address:
Background: Inflammation may play an important pathophysiological role in the development and progression of heart failure (HF). Interleukin (IL)-6 is a circulating cytokine and is the main regulator of the release of C-reactive protein (CRP).
Objectives: The authors examined the association between IL-6 and high-sensitivity (hs)-CRP and outcomes in patients with HFrEF in the DAPA-HF trial and their relationship with the effect of dapagliflozin.
Nat Commun
March 2025
Department of Physics and Astronomy, Extreme Quantum Materials Alliance, Smalley-Curl Institute, Rice University, Houston, Texas, 77005, USA.
Strong correlations in matter promote a landscape of quantum phases and associated quantum critical points. For metallic systems, there is increasing recognition that the quantum criticality goes beyond the Landau framework and, thus, further means are needed to characterize the quantum critical fluid. Here we do so by studying an entanglement quantity, the quantum Fisher information, in a strange metal system, focusing on the exemplary case of an Anderson/Kondo lattice model near its Kondo destruction quantum critical point.
View Article and Find Full Text PDFPhys Rev Lett
February 2025
Boston University, Department of Physics, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA.
We study the Heisenberg S=1/2 chain with random ferro- and antiferromagnetic couplings using quantum Monte Carlo simulations at ultra-low temperatures, converging to the ground state. Finite-size scaling of correlation functions and excitation gaps demonstrate an exotic critical state in qualitative agreement with previous strong-disorder renormalization group calculations but with scaling exponents depending on the coupling distribution. We find dual scaling regimes of the transverse correlations versus the distance, with an L independent form C(r)=r^{-μ} for r≪L and C(r,L)=L^{-η}f(r/L) for r/L>0, where μ>η and the scaling function is delivered by our analysis.
View Article and Find Full Text PDFPhys Rev Lett
February 2025
Institute of Physics, Chinese Academy of Sciences, Beijing National Laboratory for Condensed Matter Physics, Key Laboratory for Nanoscale Physics and Devices, Beijing, 100190, China.
Nonlinear photogalvanic effects in two-dimensional materials, particularly the nonlinear circular photocurrents (NCPs) that belong to the helicity-dependent spin photocurrents, have sparked enormous research interest. Although notable progress has been witnessed, the underling origin of NCPs remains elusive. Here, we present systematic photocurrent characteristics, symmetry analysis and theoretical calculations to uncover the physical origin of NCPs in MoS_{2}, a prototypical 2D semiconductor.
View Article and Find Full Text PDFPhys Rev Lett
February 2025
University of Kaiserslautern-Landau, Physics Department and Research Center OPTIMAS, D-67663 Kaiserslautern, Germany.
We study the onset of collective spin self-organization in a thermal ensemble of driven two-level atoms confined in an optical cavity. The atoms spontaneously form a spin pattern above a critical driving strength that sets a threshold and is determined by the cavity parameters, the initial temperature, and the transition frequency of the atomic spin. Remarkably, we find that inhomogeneous Doppler broadening facilitates the onset of spin self-organization.
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