Two-strand ladder network variants: Localization, multifractality, and quantum dynamics under an Aubry-André-Harper kind of quasiperiodicity

IF 2.8 3区 物理与天体物理 Q2 PHYSICS, CONDENSED MATTER
Sougata Biswas
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Abstract

In this paper we demonstrate, using a couple of variants of a two-strand ladder network that, a quasiperiodic Aubry-André-Harper (AAH) modulation applied to the vertical strands, mimicking a deterministic distortion in the network, can give rise to certain exotic features in the electronic spectrum of such systems. While, for the simplest ladder network all the eigenstates become localized as the modulation strength crosses a threshold, for the second variant, modeling an ultrathin graphene nano-ribbon, the central part of the energy spectrum remains populated by extended wavefunctions. The multifractal character in the energy spectrum is observed for both these networks close to the critical values of the modulation. We substantiate our findings also by studying the quantum dynamics of a wave packet on such decorated lattices. Interestingly, while the mean square displacement (MSD) changes in the usual manner in a pure two-strand ladder network as the modulation strength varies, for the ultrathin graphene nanoribbon the temporal behavior of the MSD remains unaltered only up to a strong modulation strength. This, we argue, is due to the extendedness of the wavefunction at the central part of the energy spectrum. Other measurements like the return probability, temporal autocorrelation function, the time dependence of the inverse participation ratio, and the information entropy are calculated for both networks with different modulation strengths and corroborate our analytical findings.
双链梯形网络变体:奥布里-安德烈-哈珀类准周期性下的定位、多分形和量子动力学
在本文中,我们利用双链梯形网络的几个变体证明,对垂直链进行准周期奥布里-安德烈-哈珀(AAH)调制,模拟网络中的确定性畸变,可以在此类系统的电子频谱中产生某些奇特的特征。对于最简单的梯形网络,当调制强度越过阈值时,所有的特征态都会局部化;而对于第二种变体,即超薄石墨烯纳米带模型,能谱的中心部分仍然由扩展波函数填充。在接近调制临界值时,这两种网络都能观察到能谱中的多分形特征。我们还通过研究这种装饰晶格上波包的量子动力学来证实我们的发现。有趣的是,在纯双链梯形网络中,随着调制强度的变化,均方位移(MSD)会以通常的方式发生变化,而在超薄石墨烯纳米带中,MSD 的时间行为仅在调制强度较强时才会保持不变。我们认为,这是由于能谱中心部分的波函数具有扩展性。我们还计算了不同调制强度下两种网络的其他测量值,如返回概率、时间自相关函数、反参与比的时间依赖性和信息熵,并证实了我们的分析结果。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Physica B-condensed Matter
Physica B-condensed Matter 物理-物理:凝聚态物理
CiteScore
4.90
自引率
7.10%
发文量
703
审稿时长
44 days
期刊介绍: Physica B: Condensed Matter comprises all condensed matter and material physics that involve theoretical, computational and experimental work. Papers should contain further developments and a proper discussion on the physics of experimental or theoretical results in one of the following areas: -Magnetism -Materials physics -Nanostructures and nanomaterials -Optics and optical materials -Quantum materials -Semiconductors -Strongly correlated systems -Superconductivity -Surfaces and interfaces
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