In this paper we investigate the nature of quantum phase transitions between two-dimensional Dirac semimetals and ${Z}_{3}$ -ordered phases (e.g., Kekule valence-bond solid), where cubic terms of the order parameter are allowed in the quantum Landau-Ginzberg theory and the transitions are putatively first order. From large- $N$ renormalization-group (RG) analysis, we find that fermion-induced quantum critical points (FIQCPs) [Z.-X. Li et al., Nat. Commun. 8, 314 (2017)] occur when $N$ (the number of flavors of four-component Dirac fermions) is larger than a critical value ${N}_{c}$ . Remarkably, from the knowledge of space-time supersymmetry, we obtain an exact lower bound for ${N}_{c}$ , i.e., ${N}_{c}>1/2$ . (Here the ``1/2'' flavor of four-component Dirac fermions is equivalent to one flavor of four-component Majorana fermions). Moreover, we show that the emergence of two length scales is a typical phenomenon of FIQCPs and obtain two different critical exponents, i.e., $\ensuremath{\nu}\ensuremath{\ne}{\ensuremath{\nu}}^{\ensuremath{'}}$, by large- $N$ RG calculations. We further give a brief discussion of possible experimental realizations of FIQCPs.In this paper we investigate the nature of quantum phase transitions between two-dimensional Dirac semimetals and ${Z}_{3}$-ordered phases (e.g., Kekule valence-bond solid), where cubic terms of the order parameter are allowed in the quantum Landau-Ginzberg theory and the transitions are putatively first order. From large-$N$ renormalization-group (RG) analysis, we find that fermion-induced quantum critical points (FIQCPs) [Z.-X. Li et al., Nat. Commun. 8, 314 (2017)] occur when $N$ (the number of flavors of four-component Dirac fermions) is larger than a critical value ${N}_{c}$. Remarkably, from the knowledge of space-time supersymmetry, we obtain an exact lower bound for ${N}_{c}$, i.e., ${N}_{c}>1/2$. (Here the ``1/2'' flavor of four-component Dirac fermions is equivalent to one flavor of four-component Majorana fermions). Moreover, we show that the emergence of two length scales is a typical phenomenon of FIQCPs and obtain two different critical exponents, i.e., $\ensuremath{\nu}\ensuremath{\ne}{\ensuremath{\nu}}^{\ensuremath{'}}$, by large-$N$ RG calculations. We further give a brief discussion of possible experimental realizations of FIQCPs.

arXiv:1610.07603Physical review. B./Physical review. BNov 28, 201735 citations

A metamaterial modulator based on electrically controllable electromagnetically induced transparency

Yuancheng Fan, Tong Qiao, Fuli Zhang +3 more

Electromagnetically induced transparency (EIT) is a promising technology for the enhancement of light-matter interactions, and recent demonstrations of the quantum EIT realized in artificial micro-structured medium have remarkably reduced the extreme requirement for experimental observation of EIT spectrum. In this paper, we propose to electrically control the EIT spectrum in a metamaterial for an electromagnetic modulator. A diode acting as a tunable resistor is loaded in the gap of two paired wires to inductively tune the magnetic resonance, which induces remarkable modulation on the EIT spectrum through the metamaterial sample. The experimental measurements confirmed that the prediction of electromagnetic modulation in three narrow bands on the EIT spectrum, and a modulation contrast of up to 31 dB was achieved on the transmission through the metamaterial. Our results may facilitate the study on active/dynamical technology in translational metamaterials, which connect extraordinary manipulations on the flow of light in metamaterials, e.g., the exotic EIT, and practical applications in industry.Electromagnetically induced transparency (EIT) is a promising technology for the enhancement of light-matter interactions, and recent demonstrations of the quantum EIT realized in artificial micro-structured medium have remarkably reduced the extreme requirement for experimental observation of EIT spectrum. In this paper, we propose to electrically control the EIT spectrum in a metamaterial for an electromagnetic modulator. A diode acting as a tunable resistor is loaded in the gap of two paired wires to inductively tune the magnetic resonance, which induces remarkable modulation on the EIT spectrum through the metamaterial sample. The experimental measurements confirmed that the prediction of electromagnetic modulation in three narrow bands on the EIT spectrum, and a modulation contrast of up to 31 dB was achieved on the transmission through the metamaterial. Our results may facilitate the study on active/dynamical technology in translational metamaterials, which connect extraordinary manipulations on the flow of light in metamaterials, e.g., the exotic EIT, and practical applications in industry.

arXiv:1605.02201May 7, 20162 citations

Remarks on Effect Algebras

W. A. Majewski, Tomasz I. Tylec

International Journal of Theoretical PhysicsDec 15, 20091 citation

On the Existence of Resonant States

Ketill Ingólfsson

North-Holland mathematics studiesJan 1, 19840 citations

In this paper we investigate the nature of quantum phase transitions between two-dimensional Dirac semimetals and

{Z}_{3}

-ordered phases (e.g., Kekule valence-bond solid), where cubic terms of the order parameter are allowed in the quantum Landau-Ginzberg theory and the transitions are putatively first order. From large-

N

renormalization-group (RG) analysis, we find that fermion-induced quantum critical points (FIQCPs) [Z.-X. Li et al., Nat. Commun. 8, 314 (2017)] occur when

N

(the number of flavors of four-component Dirac fermions) is larger than a critical value

{N}_{c}

. Remarkably, from the knowledge of space-time supersymmetry, we obtain an exact lower bound for

{N}_{c}

, i.e.,

{N}_{c}>1/2

. (Here the ``1/2'' flavor of four-component Dirac fermions is equivalent to one flavor of four-component Majorana fermions). Moreover, we show that the emergence of two length scales is a typical phenomenon of FIQCPs and obtain two different critical exponents, i.e., $\ensuremath{\nu}\ensuremath{\ne}{\ensuremath{\nu}}^{\ensuremath{'}}$, by large-

N

RG calculations. We further give a brief discussion of possible experimental realizations of FIQCPs.