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arXiv 0802.0500cond-mat.str-elhep-th
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SU(2)反铁磁体中狄拉克费米子驱动的非受限量子临界性

Deconfined quantum criticality driven by Dirac fermions in SU(2) antiferromagnets

Flavio S. Nogueira

摘要:

2+1维量子电动力学是一种有效的量子液体规范理论。近年来,在量子临界点的研究中,人们提出了一种新的电荷液体--代数电荷液体[R。K. Kaul { \it等人},Nature Physics { \bf 4},28(2008)]。在本文中,我们利用$d=4-ε$时空维中的重整化群证明了在狄拉克费米子种数为$N_f\geq 4$的SU(2)系统中存在一个去限制的量子临界点.计算是在狄拉克费米子由四分量旋量给出的表示中进行的。临界指数计算的$N_f$的几个值。特别地,对于$N_f=4$和$ε=1$($d=2+1$),Néel场的反常维数由$η_N=1/3$给出,相关长度指数为$ν=1/2$。$N_f>4$的这些值变化很大。例如,对于$N_f=6$,我们发现$η_N\approx 0.75191$和$ν\approx 0.66009$。我们还研究了手征对称性破缺的影响,并分析了手征holon极化率$G_χ(x)\equiv<\bar ψ(x)ψ(x)\bar ψ(0)ψ(0)>$的标度行为。

英文摘要:

Quantum electrodynamics in 2+1 dimensions is an effective gauge theory for the so called algebraic quantum liquids. A new type of such a liquid, the algebraic charge liquid, has been proposed recently in the context of deconfined quantum critical points [R. K. Kaul {\it et al.}, Nature Physics {\bf 4}, 28 (2008)]. In this context, we show by using the renormalization group in $d=4-ε$ spacetime dimensions, that a deconfined quantum critical point occurs in a SU(2) system provided the number of Dirac fermion species $N_f\geq 4$. The calculations are done in a representation where the Dirac fermions are given by four-component spinors. The critical exponents are calculated for several values of $N_f$. In particular, for $N_f=4$ and $ε=1$ ($d=2+1$) the anomalous dimension of the Néel field is given by $η_N=1/3$, with a correlation length exponent $ν=1/2$. These values change considerably for $N_f>4$. For instance, for $N_f=6$ we find $η_N\approx 0.75191$ and $ν\approx 0.66009$. We also investigate the effect of chiral symmetry breaking and analyze the scaling behavior of the chiral holon susceptibility, $G_χ(x)\equiv<\bar ψ(x)ψ(x)\bar ψ(0)ψ(0)>$.

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