More Like this

1. Haake–Lewenstein–Wilkens approach to spin-glasses revisited

   https://doi.org/10.1088/1751-8121/ac9d10  

   Lewenstein, Maciej; Cirauqui, David; Ángel García-March, Miguel; Guigó i Corominas, Guillem; Grzybowski, Przemysław; Saavedra, José R; Wilkens, Martin; Wehr, Jan (November 2022, Journal of Physics A: Mathematical and Theoretical)

   Abstract We revisit the Haake–Lewenstein–Wilkens approach to Edwards–Anderson (EA) model of Ising spin glass (SG) (Haakeet al1985Phys. Rev. Lett.552606). This approach consists in evaluation and analysis of the probability distribution of configurations of two replicas of the system, averaged over quenched disorder. This probability distribution generates squares of thermal copies of spin variables from the two copies of the systems, averaged over disorder, that is the terms that enter the standard definition of the original EA order parameter, $q_{\text{EA}}$ . We use saddle point/steepest descent (SPSD) method to calculate the average of the Gaussian disorder in higher dimensions. This approximate result suggest that $q_{\text{EA}}>0$ at $0<T<T_c$ in 3D and 4D. The case of 2D seems to be a little more subtle, since in the present approach energy increase for a domain wall competes with boundary/edge effects more strongly in 2D; still our approach predicts SG order at sufficiently low temperature. We speculate, how these predictions confirm/contradict widely spread opinions that: (i) There exist only one (up to the spin flip) ground state in EA model in 2D, 3D and 4D; (ii) there is (no) SG transition in 3D and 4D (2D). This paper is dedicated to the memories of Fritz Haake and Marek Cieplak. 

   more » « less
2. QCD critical point, Lee-Yang edge singularities, and Padé resummations

   https://doi.org/10.1103/PhysRevC.110.015203  

   Başar, Gökçe (July 2024, Physical Review C)

   I analyze the trajectory of the Lee-Yang edge singularities of the QCD equation of state in the complex baryon chemical potential ( ${\mu }_B$ ) plane for different values of the temperature by using the recent lattice results for the Taylor expansion coefficients up to eighth order in ${\mu }_B$ and various resummation techniques that blend in Padé expansions and conformal maps. By extrapolating from this information, I estimate for the location of the QCD critical point: $T_c\approx 100$ MeV, ${\mu }_c\approx 580$ MeV. I also estimate the crossover slope at the critical point to be ${\alpha }_1\approx 9^{\circ }$ and further constrain the nonuniversal mapping parameters between the three-dimensional Ising model and QCD equations of state. Published by the American Physical Society2024 

   more » « less
3. Connection probabilities of multiple FK-Ising interfaces

   https://doi.org/10.1007/s00440-024-01269-1  

   Feng, Yu; Peltola, Eveliina; Wu, Hao (June 2024, Probability Theory and Related Fields)

   Abstract We find the scaling limits of a general class of boundary-to-boundary connection probabilities and multiple interfaces in the critical planar FK-Ising model, thus verifying predictions from the physics literature. We also discuss conjectural formulas using Coulomb gas integrals for the corresponding quantities in general critical planar random-cluster models with cluster-weight$${q \in [1,4)}$$ $q\in [1,4)$ . Thus far, proofs for convergence, including ours, rely on discrete complex analysis techniques and are beyond reach for other values ofqthan the FK-Ising model ($$q=2$$ $q=2$ ). Given the convergence of interfaces, the conjectural formulas for other values ofqcould be verified similarly with relatively minor technical work. The limit interfaces are variants of$$\text {SLE}_\kappa $$ ${\text{SLE}}_{\kappa }$ curves (with$$\kappa = 16/3$$ $\kappa =16/3$ for$$q=2$$ $q=2$ ). Their partition functions, that give the connection probabilities, also satisfy properties predicted for correlation functions in conformal field theory (CFT), expected to describe scaling limits of critical random-cluster models. We verify these properties for all$$q \in [1,4)$$ $q\in [1,4)$ , thus providing further evidence of the expected CFT description of these models. 

   more » « less
4. Absence of $E_{2g}$ Nematic Instability and Dominant $A_{1g}$ Response in the Kagome Metal ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$

   https://doi.org/10.1103/PhysRevX.14.031015  

   Liu, Zhaoyu; Shi, Yue; Jiang, Qianni; Rosenberg, Elliott W; DeStefano, Jonathan M; Liu, Jinjin; Hu, Chaowei; Zhao, Yuzhou; Wang, Zhiwei; Yao, Yugui; et al (July 2024, Physical Review X)

   Ever since the discovery of the charge density wave (CDW) transition in the kagome metal ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ , the nature of its symmetry breaking has been under intense debate. While evidence suggests that the rotational symmetry is already broken at the CDW transition temperature ( $T_{\mathrm{CDW}}$ ), an additional electronic nematic instability well below $T_{\mathrm{CDW}}$ has been reported based on the diverging elastoresistivity coefficient in the anisotropic channel ( $m_{E_{2g}}$ ). Verifying the existence of a nematic transition below $T_{\mathrm{CDW}}$ is not only critical for establishing the correct description of the CDW order parameter, but also important for understanding low-temperature superconductivity. Here, we report elastoresistivity measurements of ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ using three different techniques probing both isotropic and anisotropic symmetry channels. Contrary to previous reports, we find the anisotropic elastoresistivity coefficient $m_{E_{2g}}$ is temperature independent, except for a step jump at $T_{\mathrm{CDW}}$ . The absence of nematic fluctuations is further substantiated by measurements of the elastocaloric effect, which show no enhancement associated with nematic susceptibility. On the other hand, the symmetric elastoresistivity coefficient $m_{A_{1g}}$ increases below $T_{\mathrm{CDW}}$ , reaching a peak value of 90 at $T^{*}=20\mathrm{K}$ . Our results strongly indicate that the phase transition at $T^{*}$ is not nematic in nature and the previously reported diverging elastoresistivity is due to the contamination from the $A_{1g}$ channel. Published by the American Physical Society2024 

   more » « less
5. Random transverse and longitudinal field Ising chains

   https://doi.org/10.1088/1742-5468/adfe5a  

   Pető, Tamás; Iglói, Ferenc; Kovács, István A (September 2025, Journal of Statistical Mechanics: Theory and Experiment)

   Abstract Motivated by experimental results on compounds like ${\text{LiHo}}_x{\text{Y}}_{1-x}{\text{F}}_4$ , we consider an Ising chain with random bonds in the simultaneous presence of random transverse and longitudinal fields. We study the low-energy properties of the model at zero temperature by the strong disorder renormalisation group method. In the absence of random longitudinal fields, the model showcases a trivial quantum-ordered and quantum-disordered fixed-point and a non-trivial infinite disorder critical point. In the absence of random transverse fields, the behaviour is dictated by the classical random-field Ising fixed-point. In the simultaneous presence of both a longitudinal and transverse random field, the RG trajectories are attracted to a set of disordered fixed-points, in which the disorder is either due to random quantum fluctuations, or due to classical random-field effects. Between the two regimes there is a smooth cross-over, which becomes sharp at the infinite disorder fixed-point. This local separatrix defines the relevant scaling direction, where the correlation-length is shown to diverge with an exponent ${\nu }_h\approx 1$ . 

   more » « less