在离子晶格上的全息费米子与反常顺磁序

Holographic pinning

In a holographic probe-brane model exhibiting a spontaneously spatially modulated ground state, we introduce explicit sources of symmetry breaking in the form of ionic and antiferromagnetic lattices. For the first time in a holographic model, we demonstrate pinning, in which the translational Goldstone mode is lifted by the introduction of explicit sources of translational symmetry breaking. The numerically computed optical conductivity fits very well to a Drude-Lorentz model with a small residual metallicity, precisely matching analytic formulas for the DC conductivity. We also find an instab…

Commensurate lock-in in holographic non-homogeneous lattices

We consider the spontaneous formation of striped structures in a holographic model which possesses explicit translational symmetry breaking, dual to an ionic lattice with spatially modulated chemical potential. We focus on the perturbative study of the marginal modes which drive the transition to a phase exhibiting spontaneous stripes. We study the wave-vectors of the instabilities with largest critical temperature in a wide range of backgrounds characterized by the period and the amplitude of the chemical potential modulation. We report the first holographic observation of the commensurate lo…

全息晶格费米液体

Holographic Fermionic Liquid with Lattices

本文研究了在较低温度的引力晶格背景下的全息费米子。由于旋转对称性在平面上被破坏，晶格效应将第一布里渊区内的费米表面的形状从圆形改变为椭圆形。当费米面与布里渊区边界相交时，通过数值分析观察到具有带隙的能带结构。我们构造了一个由标量场产生的晶格模型和一个没有标量场的离子晶格模型。在这两种情况下，我们发现了相似的物理结果。

Holographic Fermi surfaces in charge density wave from D2-D8

D2-D8 model admits a numerical solution that corresponds to a charge density wave and a spin density wave. Considering that as the background, we numerically solve the Dirac equation for probe fermions. From the solution, we obtain the Green's function and study the behaviour of the spectral density. We begin with generic fermions and have studied the formation of the Fermi surface and where it develops a gap. In addition, we have incorporated an ionic lattice and study its effect on the Fermi surface. Then we analysed the worldvolume fermions. In this particular model we do not find Fermi sur…

条纹相中的全息费米子

Holographic Fermions in Striped Phases

本文用数值方法求解含离子晶格的自发条纹全息背景中的探针费米子 Dirac 方程，揭示显式晶格增强会使 Fermi 面沿破缺方向展宽并分裂为 Fermi 弧状片段。

Isolated zeros destroy Fermi surface in holographic models with a lattice

We study the fermionic spectral density in a strongly correlated quantum system described by a gravity dual. In the presence of periodically modulated chemical potential, which models the effect of the ionic lattice, we explore the shapes of the corresponding Fermi surfaces, defined by the location of peaks in the spectral density at the Fermi level. We find that at strong lattice potentials sectors of the Fermi surface are unexpectedly destroyed and the Fermi surface becomes an arc-like disconnected manifold. We explain this phenomenon in terms of a collision of the Fermi surface pole with ze…

全息晶格上的光发射“实验”

Photoemission "experiments" on holographic lattices

本研究构建带超尺度破坏红外几何的二维全息离子晶格，研究其单电子谱的三峰结构，发现全息格林函数可较好拟合Hubbard模型格林函数，但二者深层关联仍存疑问。

Thermoelectric transport properties of gapless pinned charge density waves

Quantum strongly correlated matter exhibits properties which are not easily explainable in the conventional framework of Fermi liquids. Universal effective field theory tools are applicable in these cases regardless of the microscopic details of the quantum system, since they are based on symmetries. It is necessary, however, to construct these effective tools in full generality, avoiding restrictions coming from particular microscopic descriptions which may inadequately constrain the coefficients that enter in the effective theory. In this work we demonstrate on explicit examples how the nove…

Einstein-Maxwell-Dilaton引力中的全息晶格

Holographic Lattice in Einstein-Maxwell-Dilaton Gravity

在四维时空中，我们在爱因斯坦-麦克斯韦-爱因斯坦理论的框架下构造了一个离子晶格背景。本文研究了双场论在边界上的光电导率。由于晶格效应，我们发现电导率的虚部在零频率极限下被明显抑制，而DC电导率接近有限值，使得先前反映平移对称性的δ函数不存在。这种行为在低频下完全符合Drude定律。此外，我们还发现，在中频区域，电导率的模量呈现幂律行为。我们的结果进一步支持了Horowitz、Santos和Tong在Einstein-Maxwell理论中揭示的这种幂律行为的普遍性。

Q晶格上的全息超导体

Holographic Superconductor on Q-lattice

我们构造了Q格上超导体的最简单引力对偶模型。分析了带电标量场凝聚的临界温度存在的条件。与离子晶格上的全息超导体相比，Q晶格的存在将抑制标量场的凝聚，降低临界温度。特别地，当Q晶格背景与深绝缘相对偶时，对于一些小电荷，凝聚将永远不会发生。此外，我们数值计算的超导制度的光导。事实证明，Q晶格的存在并没有消除电导率虚部中的极点，从而确保在实部中出现δ函数。我们还评估了间隙，这在一般情况下取决于电荷的标量场以及Q-晶格参数。然而，当标量场的电荷相对较大并接近探测极限时，带隙变得与$ω_g \simeq 9T_c$普适，这与传统全息超导体的结果一致。