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arXiv 2009.05055cond-mat.str-elcond-mat.mes-hallhep-th
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三维相互作用Dirac液体中涌现的手征对称性

Emergent chiral symmetry in a three-dimensional interacting Dirac liquid

Andras Szabo, Bitan Roy

摘要:

我们计算了强Hubbard局域电子相互作用对三维四分量无质量Dirac费米子的影响,在无相互作用系统中,Dirac费米子具有微观整体U(1)$\otimes$ SU(2)手征对称性.一个具体的晶格实现这样的手征狄拉克激发,和电子-电子相互作用的作用进行了研究,通过执行场论重整化群(RG)分析,控制由\emph{small}参数$ε$与$ε=d-1$,关于较低的临界一个空间维度。除了非相互作用的高斯不动点外,该系统在非零相互作用耦合$\sim ε$处支持四个量子临界点和四个双临界点。即使手征对称性在相互作用模型中不存在,它也会在不同的RG固定点处作为涌现现象得到恢复(部分或全部)。整体相图的代表性切割显示了标量和赝标量激子和超导(例如$s$ -波和$p$ -波)质量有序相的汇合,表明恢复了(a)排斥相互作用的两个激子质量之间的手征U(1)对称性和(b)吸引相互作用的标量或赝标量激子和超导质量之间的赝自旋SU(2)对称性。最后,我们微扰地研究了\emph{weak}旋转对称破缺对各种RG不动点稳定性的影响。

英文摘要:

We compute the effects of strong Hubbardlike local electronic interactions on three-dimensional four-component massless Dirac fermions, which in a noninteracting system possess a microscopic global U(1)$\otimes$SU(2) chiral symmetry. A concrete lattice realization of such chiral Dirac excitations is presented, and the role of electron-electron interactions is studied by performing a field theoretic renormalization group (RG) analysis, controlled by a \emph{small} parameter $ε$ with $ε=d-1$, about the lower-critical one spatial dimension. Besides the noninteracting Gaussian fixed point, the system supports four quantum critical and four bicritical points at nonvanishing interaction couplings $\sim ε$. Even though the chiral symmetry is absent in the interacting model, it gets restored (either partially or fully) at various RG fixed points as emergent phenomena. A representative cut of the global phase diagram displays a confluence of scalar and pseudoscalar excitonic and superconducting (such as the $s$-wave and $p$-wave) mass ordered phases, manifesting restoration of (a) chiral U(1) symmetry between two excitonic masses for repulsive interactions and (b) pseudospin SU(2) symmetry between scalar or pseudoscalar excitonic and superconducting masses for attractive interactions. Finally, we perturbatively study the effects of \emph{weak} rotational symmetry breaking on the stability of various RG fixed points.

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