scholarly journals Helical symmetry breaking and quantum anomaly in massive Dirac fermions

2021 ◽  
Vol 104 (24) ◽  
Author(s):  
Huan-Wen Wang ◽  
Bo Fu ◽  
Shun-Qing Shen
Keyword(s):  
Symmetry Breaking ◽  
Dirac Fermions ◽  
Helical Symmetry ◽  
Quantum Anomaly

Study on the Nanoconfinement-Induced Breaking of Helical Symmetry in Metal Nanowires

2011 ◽  
Vol 418-420 ◽  
pp. 313-316
Author(s):  
Yan Wei ◽  
Lin Jiang ◽  
Gui Kao Yang ◽  
Ting Wang ◽  
Yan Zhang
Keyword(s):  
Symmetry Breaking ◽  
Rotational Symmetry ◽  
Critical Value ◽  
Metal Nanowires ◽  
Energy Minimum ◽  
Free Standing ◽  
Helical Symmetry ◽  
Metal Atoms

Metal atoms confined in finite cylindrical nanopores exhibit helical morphologies because of the high rotational symmetry of confined surfaces and energy minimum of (111) facets. Herein, we present adirect nanoconfinement induced helical symmetry breaking phenomenon resulting from asymmetric atomic arrangements around the surfaces of nanoconfinements. In cylindrical nanopores, the critical value transforming from helical nanowires to crystalline ones is larger than corresponding free-standing nanowires, indicating nanopores with high rotational symmetry are propitious to form (111)facets wrapped outside of nanowires

scholarly journals Quantum diffusion of massive Dirac fermions induced by symmetry breaking

2021 ◽  
Vol 104 (7) ◽  
Author(s):  
Ting Zhang ◽  
Chushun Tian ◽  
Ping Sheng
Keyword(s):  
Symmetry Breaking ◽  
Quantum Diffusion ◽  
Dirac Fermions

scholarly journals Cascade of phase transitions in a planar Dirac material

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Takuya Kanazawa ◽  
Mario Kieburg ◽  
Jacobus J.M. Verbaarschot
Keyword(s):  
Phase Diagram ◽  
Phase Transitions ◽  
Symmetry Breaking ◽  
Ground State ◽  
Chemical Potential ◽  
Three Dimensional ◽  
Dirac Fermions ◽  
First Order ◽  
First Order Phase ◽  
Parity Breaking

Abstract We investigate a model of interacting Dirac fermions in 2 + 1 dimensions with M flavors and N colors having the U(M)×SU(N ) symmetry. In the large-N limit, we find that the U(M) symmetry is spontaneously broken in a variety of ways. In the vacuum, when the parity-breaking flavor-singlet mass is varied, the ground state undergoes a sequence of M first-order phase transitions, experiencing M + 1 phases characterized by symmetry breaking U(M)→U(M − k)×U(k) with k ∈ {0, 1, 2, · · · , M}, bearing a close resemblance to the vacuum structure of three-dimensional QCD. At finite temperature and chemical potential, a rich phase diagram with first and second-order phase transitions and tricritical points is observed. Also exotic phases with spontaneous symmetry breaking of the form as U(3)→U(1)3, U(4)→U(2)×U(1)2, and U(5)→U(2)2×U(1) exist. For a large flavor-singlet mass, the increase of the chemical potential μ brings about M consecutive first-order transitions that separate the low-μ phase diagram with vanishing fermion density from the high-μ region with a high fermion density.

Gross–Neveu–Yukawa and Gross–Neveu models

2021 ◽  
pp. 489-506
Author(s):  
Jean Zinn-Justin
Keyword(s):  
Phase Transition ◽  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Particle Physics ◽  
Continuous Phase ◽  
Two Dimensions ◽  
Fermion Mass ◽  
Dirac Fermions ◽  
Mass Generation ◽  
Four Dimensions

In this chapter, a model is considered that can be defined in continuous dimensions, the Gross– Neveu–Yukawa (GNY) model, which involves N Dirac fermions and one scalar field. The model has a continuous U(N) symmetry, and a discrete symmetry, which prevents the addition of a fermion mass term to the action. For a specific value of a coefficient of the action, the model undergoes a continuous phase transition. The broken phase illustrates a mechanism of spontaneous symmetry breaking, leading to spontaneous fermion mass generation like in the Standard Model (SM) of particle physics. In four dimensions, the GNY can be considered as a toy model to represent the interactions between the top quark and the Higgs boson, the heaviest particles of the SM of fundamental interactions, when the gauge fields are omitted. The model is renormalizable in four dimensions and its renormalization group (RG) properties can be studied in d = 4 and d = 4 − ϵ dimensions. A model of self-interacting fermions with the same symmetries and fermion content, the Gross–Neveu (GN) model, has been widely studied. In perturbation theory, for d > 2, it describes only a phase with massless fermions but, in d = 2 + ϵ dimensions, the RG indicates that, at a critical value of the coupling constant, the model experiences a phase transition. In two dimensions, it is renormalizable and exhibits the phenomenon of asymptotic freedom. The massless phase becomes infrared unstable and there is strong evidence that the spectrum corresponds to spontaneous symmetry breaking and fermion mass generation.

scholarly journals Superconductivity, correlated insulators, and Wess–Zumino–Witten terms in twisted bilayer graphene

2020 ◽  
Vol 117 (47) ◽  
pp. 29543-29554
Author(s):  
Maine Christos ◽  
Subir Sachdev ◽  
Mathias S. Scheurer
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Band Structure ◽  
Symmetry Breaking ◽  
Bilayer Graphene ◽  
Flavor Symmetry ◽  
Dirac Fermions ◽  
Parent State ◽  
Comprehensive Listing ◽  
Twisted Bilayer Graphene

Recent experiments on twisted bilayer graphene have shown a high-temperature parent state with massless Dirac fermions and broken electronic flavor symmetry; superconductivity and correlated insulators emerge from this parent state at lower temperatures. We propose that the superconducting and correlated insulating orders are connected by Wess–Zumino–Witten terms, so that defects of one order contain quanta of another order and skyrmion fluctuations of the correlated insulator are a “mechanism” for superconductivity. We present a comprehensive listing of plausible low-temperature orders and the parent flavor symmetry-breaking orders. The previously characterized topological nature of the band structure of twisted bilayer graphene plays an important role in this analysis.

Sign in / Sign up

Export Citation Format

Share Document