Konstantin Semeniuk, Hui Chang, Jordan Baglo, Sven Friedemann, Audrey Grockowiak, William A. Coniglio, Monika B. Gamża, Pascal Reiss, Patricia Alireza, Inge Lee… 展开作者
Konstantin Semeniuk, Hui Chang, Jordan Baglo, Sven Friedemann, Audrey Grockowiak, William A. Coniglio, Monika B. Gamża, Pascal Reiss, Patricia Alireza, Inge Leermakers, Alix McCollam, Stan Tozer, F. Malte Grosche
Metal-insulator transitions in clean, crystalline solids can be driven by two distinct mechanisms. In a conventional insulator, the charge carrier concentration vanishes, when an energy gap separates filled and unfilled electronic states. In the established picture of a Mott insulator, by contrast, electronic interactions cause coherent charge carriers to slow down and eventually stop in electronic grid-lock without materially affecting the carrier concentration itself. This description has so far escaped experimental verification by quantum oscillation measurements, which directly probe the velocity distribution of the coherent charge carriers. By extending this technique to high pressure we were able to examine the evolution of carrier concentration and velocity in the strongly correlated metallic state of the clean, crystalline material NiS$_2$, while tuning the system towards the Mott insulating phase. Our results confirm that pronounced electronic slowing down indeed governs the approach to the insulating state. However, the critical point itself, at which the carrier velocity would reach zero and the effective carrier mass diverge, is concealed by the insulating sector of the phase diagram. In the resulting, more nuanced view of Mott localisation, the inaccessibility of the low temperature Mott critical point resembles that of the threshold of magnetic order in clean metallic systems, where criticality is almost universally interrupted by first order transitions, tricritical behaviour or novel emergent phases such as unconventional superconductivity.
We consider the interaction-driven Mott transition at zero temperature from the viewpoint of microscopic Fermi liquid theory. To this end, we derive an exact expression for the Landau parameters within the dynamical mean-field theory (DMFT) approximation to the single-band Hubbard model. At the Mott transition the symmetric and the anti-symmetric Landau parameter diverge. The vanishing compressibility at the Mott transition directly implies the divergence of the forward scattering amplitude in the charge sector, which connects the proximity of the Mott phase to a tendency towards phase separat…
Non-perturbative landscape of the Mott-Hubbard transition: Multiple divergence lines around the critical endpoint
我们分析了高度非微扰制度周围的Mott-Hubbard金属到绝缘体转变（MIT）的动力学平均场论计算在两个粒子的水平。通过推广Schäfer等人[Phys. Rev. Lett. 110，246405（2013）]我们证明了哈伯德模型的相图中存在无限多条线，其中局部Bethe-Salpeter方程和相关的不可约顶点函数在电荷以及粒子-粒子通道中变得奇异。这些发散线积累的关键莫特端点根据解释为前体的麻省理工学院。通过将我们的数值计算结果与越来越复杂的解析计算结果进行比较，如无序二元混合模型、Falicov-Kimball（FK）模型以及原子极限（AL）模型，（i）我们识别出两种不同的发散线，（ii）我们根据相关奇异本征向量的频率结构对它们进行了分类，（iii）我们发现了两种不同的发散线。（iii）我们研究了它们与Luttinger-Ward形式主义中多分支的关系。此外，我们可以区分两种情况，一种是多重发散仅仅反映了一个潜在的、唯一的能量标度$ν^*$的出现，在这个标度之下，微扰理论不再适用;另一种是微扰理论的崩溃对不同的能量体系产生了重要影响。最后，我们讨论了我们的研究结果的理论理解的MIT周围的非微扰物理和适用于该制度的多体算法的未来发展的影响。
The Mott transition is usually considered as resulting from the divergence of the effective mass of the quasiparticle in the Fermi-liquid theory; the dispersion relation around the Fermi level is considered to become flat towards the Mott transition. Here, to clarify the characterization of the Mott transition under the assumption of a Fermi-liquid-like ground state, the electron-addition excitation from the Gutzwiller wavefunction in the $t$-$J$ model is investigated on a chain, ladder, square lattice, and bilayer square lattice in the single-mode approximation using a Monte Carlo method. The…
Properties of the doped spin 3/2 Mott insulator near half filling
本文对自旋为3/2的哈伯德模型在半填充附近具有大的反Hunds规则耦合的情形，给出了一个精确的广义Bogoliubov变换.由于我们的变换是么正的，因此我们可以在全希尔伯特空间中采用标准的近似平均场理论方法来分析掺杂的莫特绝缘体，这与基于截断希尔伯特空间补充硬核约束的传统方法相反。在完全半填充的基态是绝缘（莫特）单态，根据我们的分析，非费米液体序参量$ Δ$通常与扩展的s波超导性，将出现自洽尽快有限密度$ n $孔被引入。非费米液体行为是将Mott单重态映射到Fock真空的幺正变换的非线性性质的结果，该幺正变换在有效拉格朗日量中引入了诸如$Δn$的反常项。我们的分析使用的方法，很容易推广到多带哈伯德模型，并可以提供一种机制，即非费米液体序参量的密度成正比的莫特绝缘体与局部纠缠基态。对于更复杂的系统，这样的序参量可以自然地与各种其他序参量共存。
Dynamically driven interacting quantum many-body systems have the potential to exhibit properties that defy the laws of equilibrium statistical mechanics. A widely studied model is the impulsively driven antiferromagnetic Mott insulator, which is predicted to realize exotic transient phenomena including dynamical phase transitions into thermally forbidden states and highly non-thermal magnon distributions. However such far-from-equilibrium regimes, where conventional time-dependent Ginzburg-Landau descriptions fail, are experimentally challenging to prepare and to probe especially in solid sta…
Here we analyze the divergences of the irreducible vertex function in dynamical mean field theory, which may indicate either a non-physical breakdown of the perturbation theory or a response to some physical phenomenon. To investigate this question, we construct a quasiparticle vertex from the diverging irreducible vertex functions. This vertex describes the scattering between quasiparticles and quasiholes in a Fermi liquid. We show that the quasparticle vertex \textit{does not} diverge in the charge channel, wherein the irreducible vertex \textit{does} diverge; and we show that the quasiparti…
While the breakdown of the perturbation expansion for the many-electron problem has several formal consequences, here we unveil its physical effect: Flipping the sign of the effective electronic interaction in specific scattering channels. By decomposing local and uniform susceptibilities of the Hubbard model via their spectral representations, we prove how entering the non-perturbative regime causes an enhancement of the charge response, ultimately responsible for the phase-separation instabilities close to the Mott MIT. Our analysis opens a new route for understanding phase-transitions in th…
We study the effects of electron-electron interactions and hole doping on the electronic structure of Cu-doped NaFeAs using the density functional theory plus dynamical mean-field theory (DFT+DMFT) method. In particular, we employ an effective multi-orbital Hubbard model with a realistic bandstructure of NaFeAs in which Cu-doping was modeled within a rigid band approximation and compute the evolution of the spectral properties, orbital-dependent electronic mass renormalizations, and magnetic properties of NaFeAs upon doping with Cu. In addition, we perform fully charge self-consistent DFT+DMFT…
We analyze multi-orbital Hubbard models describing Hund's metals, focusing on the ubiquitous occurrence of a charge instability, signalled by a divergent/negative electronic compressibility, in a range of doping from the half-filled Mott insulator corresponding to the frontier between Hund's and normal metals. We show that the breaking of rotational invariance favors this instability: both spin-anisotropy in the interaction and crystal-field splitting among the orbitals make the instability zone extend to larger dopings, making it relevant for real materials like iron-based superconductors. Th…
