We explore layered strongly correlated materials as a platform to identify and control unconventional heat transfer phenomena. We demonstrate that these systems can be tailored to sustain a wide spectrum of heat transport regimes, ranging from ballistic, to hydrodynamic all the way to diffusive. Within the hydrodynamic regime, wave-like temperature oscillations are predicted up to room temperature. All the above phenomena have a purely electronic origin, stemming from the existence of two components in the electronic system, each one thermalized at different temperatures. The interaction strength can be exploited as a knob to control the different thermal transport regimes. The present results pave the way to transition-metal oxide heterostructures as building blocks for nanodevices exploiting the wave-like nature of heat transfer on the picosecond time scale.
ω/T scaling of the optical conductivity in strongly correlated layered cobalt oxide
报道了强关联层状钴氧化物[BiBa $_{0.66}$ K $_{0.36}$ O $_2$ ]CoO $_2$的红外光谱性质。在单晶上进行的这些测量使我们能够确定作为温度的函数的光学电导率。除了谱权随温度的变化外，还发现了一个非常规的低能模，它的频率和阻尼尺度都随温度的变化而变化。事实上，基本分析表明，该模式完全缩放到$ω$ /T的函数，直到室温。这种行为表明，低能量激发的非费米液体类型起源于量子临界。
Layered ferromagnets are thrilling materials from both a fundamental and technological point of view. VI3 is an interesting example, with a complex magnetism that differentiates it from the first reported Cr based layered ferromagnets. Here, we show in an indirect way through Angle Resolved Photoemission Spectroscopy (ARPES) experiments, the importance of spin-orbit coupling setting the electronic properties of this material. Our light polarized photoemission measurements point to a ground state with a half-filled e'_+- doublet, where a gap opening is triggered by spin-orbit coupling enhanced …
Pseudogap formation in the moderate correlated layered attractive Hubbard model
Russian Quantum Center（俄罗斯量子中心）；National University of Science and Technology “MISIS”（莫斯科国立科技大学 MISIS）；Department of Physics, National Research University Higher School of Economics（高等经济大学物理系）；Lomonosov Moscow State University（莫斯科国立罗蒙诺索夫大学）；London School of Economics and Political Science（伦敦政治经济学院）
The recent observation of superconductivity in an infinite-layer and quintuple-layer nickelate within the same $R_{n+1}$Ni$_{n}$O$_{2n+2}$ series ($R$ = rare-earth, $n=2-\infty$, with $n$ indicating the number of NiO$_{2}$ layers along the $c$-axis), unlocks their potential to embody a whole family of unconventional superconductors. Here, we systematically investigate the many-body electronic structure of the layered nickelates (with $n=2-6,\infty$) within a density-functional theory plus dynamical mean-field theory framework and contrast it with that of the known superconducting members of th…
We investigate the crystal structure and the electronic properties of the trilayer nickelate La$_4$Ni$_3$O$_{10}$ by means of quantum mechanical calculations in the framework of the density functional theory. We find that, at low temperature, La$_4$Ni$_3$O$_{10}$ undergoes a hitherto unreported structural phase transition and transforms to a new monoclinic $P2_1/a$ phase. This phase exhibits electronic properties in agreement with recent angle-resolved photoemission spectroscopy data reported in H.\ Li \emph{et al}., Nat.\ Commun.\ \textbf{8}, 704 (2017) and should be considered in models focu…
Factors affecting the topological Hall effect in strongly correlated layered magnets: spin of the magnetic atoms, polar and azimuthal angle subtended by the spin texture
This article provides an overview, primarily from an experimental perspective, of recent progress and future prospects in using helium to realize a range of quantum materials of generic interest, by "top-down" and "bottom-up" nanotechnology. We can grow model systems to realise new quantum states of matter, and explore key issues in condensed matter physics. In the language of cold atomic gases, two dimensional and confined 3He and 4He provide "quantum simulators", with the potential to uncover new emergent quantum states. These include: strictly 2D Fermi system with Mott-Hubbard transition; i…
A polymorph of RuI$_3$ synthesized under high pressure was found to have a two-layered honeycomb structure. The resistivity of RuI$_3$ exhibits a semimetallic behavior, in contrast to insulating properties in $α$-RuCl$_3$. In addition, Pauli paramagnetic behavior was observed in the temperature dependence of a magnetic susceptibility and a nuclear spin-lattice relaxation rate 1/$T_1$. The band structure calculations indicate that contribution of the I 5$p$ components to the low-energy $t_\mathrm{2g}$ bands effectively decreases Coulomb repulsion, leading to semimetallic properties. The physica…
Magnetic field dependent specific heat and enhanced Wilson ratio in strongly correlated layered cobalt oxide
研究了强关联层状钴氧化物[BiBa $_{0.66}$ K $_{0.36}$ O $_2$ ]CoO $_2$的低温比热随磁场的变化.这些测量揭示了两种磁场依赖的贡献与先前推断的磁量子临界点（QCP）的存在定性协议。首先，低温T $^3$的比热行为的系数原来是相当大的下降附近的磁场与临界值在最近的论文中报道的一致。此外，索末菲系数的一个温和的，但显着的增强被发现在附近的QCP表明略有增加的电子有效质量。这一结果与以前报道的泡利磁化率的发散行为形成对比。因此，一个强烈增强的威尔逊比推导出，这表明有效的费米液体制度，可以解释不寻常的磁场依赖的比热铁磁波动。作为一个强有力的检查，高磁场威尔逊比渐近恢复的普遍限制当地费米液体对铁磁性。
Resonant elastic X-ray scattering (REXS) at the Eu $M_5$ edge reveals an antiferromagnetic structure in layered EuCd$_2$Sb$_2$ at temperatures below $T_\textrm{N}$ = 7.4 K with a magnetic propagation vector of $(0,0,1/2)$ and spins in the basal plane. Magneto-transport and REXS measurements with an in-plane magnetic field show that features in the magnetoresistance are correlated with changes in the magnetic structure induced by the field. Ab initio electronic structure calculations predict that the observed spin structure gives rise to a gapped Dirac point close to the Fermi level with a gap …
Layered ruthenates are a unique class of systems which manifests a variety of electronic and magnetic features emerged from competing energy scales. At the heart of such features lies the multi-orbital physics, especially, the orbital-selective behavior. Here, we propose that the SrRuO3-SrTiO3 heterostructure is a highly tunable platform to obtain the various emergent properties. Employing the density functional theory plus dynamical mean-field theory, we thoroughly investigate the orbital-dependent physics of the system and identify the competing magnetic fluctuations. We show that the epitax…
To get insight into the nature of the electronic fluid in the frustration-driven charge glasses, we investigate in-plane and out-of-plane charge transport for several quasi-triangular-lattice organic systems, $θ$-(BEDT-TTF)$_2$X [X=RbZn(SCN)$_4$, CsZn(SCN)$_4$ and I$_3$]. These compounds host a charge order, charge glass and Fermi liquid, depending on the strength of charge frustration. We find that the resistivity exhibits extremely two-dimensional (2D) anisotropy and contrasting temperature dependence between in the in-plane and out-of-plane directions in the charge glass phase, qualitativel…
First-principles calculations and a model consideration of magnetically frustrated layered material PdCrO$_2$ are performed. The results on the exchange parameters are in agreement with the experimental data on the Curie-Weiss temperature ($θ$). We show that experimentally observed strong suppression of the Néel temperature ($T_N$) in comparison with the Curie-Weiss temperature is due to three main factors. First, as expected, this is connected with the layered structure and relatively small exchange interaction along the $c$ axis. Second, deformation of the ideal in-plane 120$^{\circ}$ magnet…
Spin correlated electronic state on the surface of a spin-orbit Mott system (Layered Iridates)
二维电子系统的新相是由新的表面或界面修饰的电子结构引起的，在材料科学中引起了极大的兴趣。我们利用光电子能谱表明，近表面的电子结构的体绝缘铱酸盐Sr $_3$ Ir $_2$ O $_7$位于附近的金属-莫特绝缘体过渡表现出弱的金属性表示有限的电子光谱重量在费米能级。表面电子表现出独特的自旋结构，由自旋轨道，库仑相互作用和表面量子磁性的相互作用，不同于拓扑绝缘体状态。我们的研究结果表明，一个新的准二维相互作用电子表面基态的实验实现，打开了大门，奇异的量子纠缠和输运现象的铱基氧化物器件。
Pressure-Tuned Competing Electronic States in Layered Tellurides
University of Sharjah（沙迦大学）；University of Doha for Science and Technology（多哈科学与技术大学）；Korzhinskii Institute of Experimental Mineralogy RAS（俄罗斯科学院科尔任斯基实验矿物学研究所）；Ural Federal University（乌拉尔联邦大学）；Qatar Environment and Energy Research Institute (QEERI), Hamad Bin Khalifa University（卡塔尔环境能源研究所（QEERI），哈利法大学）；Izmir Institute of Technology（伊兹密尔理工大学）；American University of Sharjah（沙迦美国大学）
Mesoscopic irregularly ordered and even amorphous self-assembled electronic structures were recently reported in two-dimensional metallic dichalcogenides (TMDs), created and manipulated with short light pulses or by charge injection. Apart from promising new all-electronic memory devices, such states are of great fundamental importance, since such aperiodic states cannot be described in terms of conventional charge-density-wave (CDW) physics. In this paper we address the problem of metastable mesoscopic configurational charge ordering in TMDs with a sparsely filled charged lattice gas model in…
We report electronic band structure calculations for Sr$_{4}$Ru$_{3}$O$_{10}$ that displays both ferromagnetic and metamagnetic behavior. The density functional calculations find the ground state to be ferromagnetic in agreement with the experiment and we find that the inclusion of Coulomb Hubbard interaction U applied to the Ru 4d states has dramatic effects on the Fermi surface, which reveal the role of Coulomb interactions and correlated many-body physics. The minority spin bands are mainly empty with Fermi surfaces in the outer areas of the Brillouin zone away from the $Γ$ point with bands…
The recent discovery of superconductivity in Sr-doped NdNiO$_2$, with a critical temperature of $10-15$ K suggests the possibility of a new family of nickel-based high-temperature superconductors (HTS). NdNiO$_{2}$ is the $n=\infty$ member of a larger series of layered nickelates with chemical formula R$_{n+1}$Ni$_{n}$O$_{2n+2}$ (R $=$ La, Nd, Pr; $n = 2, 3, \dots, \infty$). The $n=3$ member has been experimentally and theoretically shown to be cuprate-like and a promising HTS candidate if electron doping could be achieved. The higher-order $n=4,5,$ and $6$ members of the series fall directly …
Electronic and structural properties of Rh- and Pd-based kagome layered shandites from first principles
Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）；Department of Chemical Engineering and Materials Science, University of Minnesota（明尼苏达大学化学工程与材料科学系）
Complex electronic states in double layered ruthenates (Sr1-xCax)3Ru2O7
（Sr $_{1-x}$ Ca $_x$）$_3$ Ru $_2$ O $_7$（0 $\leq x \leq$ 1）的磁基态是复杂的，从巡回变磁态（0 $\leq x <$ 0.08）到不寻常的重质量近铁磁（FM）态（0.08 $< x <$ 0.4），最后到反铁磁（AFM）态（0.4 $\leq x \leq$ 1）。在这份报告中，我们阐明了这些磁态的电子性质，并表明，在这个系统中的电子和磁性是强耦合的。电子基态从$x =$ 1.0的AFM准二维金属演化到$0.4 \leq x < 1.0$的Anderson局域态（AFM区域）。当磁性状态经历从AFM到近FM状态的转变时，对于$0.25 \leq x < 0.4$，电子基态切换到由磁散射诱导的弱局域态，然后切换到具有面内电阻率$ρ_{ab} \propto T^α$（$α>$ 2）的磁性金属态，对于$0.08 < x < 0.25$。当磁基态进入$x < 0.08$的巡游变磁态时，系统最终转变为费米液体基态。当$x$接近临界组成（$x \sim$ 0.08）时，费米液体温度被抑制到零开尔文，并且观察到非费米液体行为。这些结果表明，在双层双链酸盐的电荷和自旋自由度之间的强烈的相互作用。
Layered kagome-lattice materials with 3$d$ transition metals provide a fertile playground for studies on geometry frustration, band topology and other novel ordered states. A representative class of materials AV$_3$Sb$_5$ (A=K, Rb, Cs) have been proved to possess various unconventional phases such as superconductivity, non-trivial $\mathbb{Z}_2$ band topology, and electronic nematicity, which are intertwined with multiple interlaced charge density waves (CDW). However, the interplay among these novel states and their mechanisms are still elusive. Recently, the discovery of isostructural titani…
Layered material structures play a key role in enhancing electron-electron interactions to create correlated metallic phases that can transform into unconventional superconducting states. The quasi-two-dimensional electronic properties of such compounds are often inferred indirectly through examination of their bulk properties. Here we use scanning tunneling microscopy and spectroscopy to directly probe in cross section the quasi-two-dimensional correlated electronic states of the heavy fermion superconductor CeCoIn5. Our measurements reveal the strong confined nature of heavy quasi-particles,…
Layered transition metal dichalcogenide 1T-NbSe_2 is a good candidate to explore the charge density wave (CDW) and Mott physics. However, the effects of stacking orders and interlayer coupling in CDW 1T-NbSe_2 are still less explored and understood. Using density functional theory calculations, we present a systematic study of the electronic and magnetic properties of monolayer and layered CDW 1T-NbSe_2. Our results indicate that monolayer CDW 1T-NbSe_2 is a magnetic insulator with \sqrt13\times\sqrt13 periodic lattice modulation. Nevertheless, the magnetic properties of bilayer CDWs 1T-NbSe_2…
Optical conductivity of layered topological semimetal TaNiTe$_5$
University of Zagreb（萨格勒布大学）；TU Wien（维也纳工业大学）；University of Fribourg（弗里堡大学）；University of West Bohemia in Pilsen（比尔森西波希米亚大学）；Brookhaven National Laboratory（布鲁克海文国家实验室）
Bulk superconductivity was discovered in BaRh2P2 (Tc = 1.0 K) and BaIr2P2 (Tc = 2.1 K), which are isostructural to (Ba,K)Fe2As2, indicative of the appearance of superconductivity over a wide variety of layered transition metal pnictides. The electronic specific heat coefficient gamma in the normal state, 9.75 and 6.86 mJ/mol K2 for BaRh2P2 and BaIr2P2 respectively, indicate that the electronic density of states of these two compounds are moderately large but smaller than those of Fe pnictide superconductors. The Wilson ratio close to 1 indeed implies the absence of strong electron correlations…
The electronic and magnetic structure, including the Heisenberg model exchange interaction parameters, was explored for the recently proposed novel cuprate Cu$_2$F$_5$. Using the DFT+U calculation, it is shown that the compound is formed by two types of copper ions with $d^9$ and $d^8$ electronic configurations. We have found a very stable antiferromagnetic ordering with strong anisotropy of exchange interaction that results in the appearance of an unusual 2D-magnetism: within the (100)-plane the exchange between the S=1 and S=1/2 Cu ions has almost the same strength as between the two S=1 ion…
Besides the chemical constituents, it is the lattice geometry that controls the most important material properties. In many interesting compounds, the arrangement of elements leads to pronounced anisotropies, which reflect into a varying degree of quasi two-dimensionality of their low-energy excitations. Here, we start by classifying important families of correlated materials according to a simple measure for the tetragonal anisotropy of their ab initio electronic (band) structure. Second, we investigate the impact of a progressively large anisotropy in driving the non-locality of many-body ef…
