The recent confirmation of closed Fermi surface in the high temperature cuprates via de Haas-van Alphen and Shubnikov-de haas oscillations calls for a theoretical investigation of the origin of such oscillations. We study de Haas-van Alphen oscillations and magnetic breakdown in the context of ortho-II high temperature cuprates to understand the origin of the multiple frequencies. We find that the magnetic breakdown is highly sensitive not only to the ortho-II potential, but also to the Fermi surface topology, and is thus useful to distinguish between various theoretical proposals related to quantum oscillations.
Studying angle-dependent magnetoresistance oscillations of cuprate superconductors in a model with antiferromagnetic reconstruction and magnetic breakdown
Magnetic Breakdown in the electron-doped cuprate superconductor Nd$_{2-x}$Ce$_x$CuO$_4$: the reconstructed Fermi surface survives in the strongly overdoped regime
本文报道了电子过掺杂铜氧化物超导体Nd $_{2-x}$ Ce $_x$ CuO $_4$中的半经典角度相关磁电阻振荡（AMRO）和Shubnikov-de Haas效应。我们的数据提供了令人信服的证据磁击穿系统。这表明，一个重建的多连接费米表面持续存在，至少在强磁场，直到超导制度的最高掺杂水平。结果表明，在电子掺杂铜氧化物超导体中，平移对称破缺与超导配对之间存在着密切的联系。
We undertake a detailed high-resolution diffraction study of a novel plain band insulator, La$_2$MgO$_4$, which may be viewed as a structural surrogate system of the undoped end-member of the high-T$_c$ superconductors, La$_{2-x-y}$A$^{2+}_x$RE$^{3+}_y$CuO$_{4}$ (A = Ba, Sr, RE= Rare Earth). We find that La$_2$MgO$_4$ exhibits the infamous low-temperature orthorhombic (LTO) to low-temperature tetragonal (LTT) phase transition that has been linked to the suppression of superconductivity in a variety of underdoped cuprates, including the well known La$_{2-x}$Ba$_{x}$CuO$_4$ ($x=0.125$). Furtherm…
Anisotropic microwave conductivity of cuprate superconductors in the presence of CuO chain induced impurities
在动能驱动的超导机制下，研究了邻位Ⅱ型$_2$的微波电导各向异性.邻位-Ⅱ $_2$ $_3$ O $_{6.50}$的特征在于填充和空$\hat{b}$轴CuO链的周期性交替。考虑CuO链诱导的扩展各向异性杂质散射，基于准粒子激发和散射过程的节块近似，再现了邻位Ⅱ型$_2$微波电导各向异性的主要特征，包括$\hat{a}$轴和$\hat{b}$轴微波电导的能量和温度依赖性的强度和线形.我们的研究结果也证实了$\hat{b}$轴CuO链诱导杂质是各向异性的主要来源。
The observation of a reconstructed Fermi surface via quantum oscillations in hole-doped cuprates opened a path towards identifying broken symmetry states in the pseudogap regime. However, such an identification has remained inconclusive due to the multi-frequency quantum oscillation spectra and complications accounting for bilayer effects in most studies. We overcome these impediments with high resolution measurements on the structurally simpler cuprate HgBa2CuO4+d (Hg1201), which features one CuO2 plane per unit cell. We find only a single oscillatory component with no signatures of magnetic …
Previously known to form only under high pressure synthetic conditions, here we report that the T'-type 214-structure cuprate based on the rare earth atom Tb is stabilized for ambient pressure synthesis through partial substitution of Pd for Cu. The new material is obtained in purest form for mixtures of nominal composition $Tb_{1.96}Cu_{0.80}Pd_{0.20}O_{4}$. The refined formula, in orthorhombic space group Pbca, with a = 5.5117(1) Å, b = 5.5088(1) Å, and c = 11.8818(1) Å, is $Tb_{2}Cu_{0.83}Pd_{0.17}O_{4}$. An incommensurate structural modulation is seen along the a axis by electron diffracti…
Cuprate superconductors still hold many open questions, in particular concerning their normal state properties, including the role of charge ordering. Nuclear magnetic resonance on $^{63,65}$Cu and $^{17}$O in the CuO$_2$ plane is a very sensitive bulk probe of charge variations, but not properly understood. Since early NMR, the oxygen satellite line splittings in YBa$_2$Cu$_3$O$_{6+y}$ were attributed to the orthorhombic distortion, while they could also be due to charge ordering. We employ high pressure NMR on YBa$_2$Cu$_3$O$_{6.9}$ hoping that charge order would respond to pressure differen…
A complicating factor in unraveling the theory of high-temperature (high-Tc) superconductivity is the presence of a "pseudogap" in the density of states, whose origin has been debated since its discovery [1]. Some believe the pseudogap is a broken symmetry state distinct from superconductivity [2-4], while others believe it arises from short-range correlations without symmetry breaking [5,6]. A number of broken symmetries have been imaged and identified with the pseudogap state [7,8], but it remains crucial to disentangle any electronic symmetry breaking from pre-existing structural symmetry o…
The iron-based high temperature superconductors share a number of similarities with their copper-based counterparts, such as reduced dimensionality, proximity to states of competing order, and a critical role for 3d electron orbitals. Their respective temperature-doping phase diagrams also contain certain commonalities that have led to claims that the metallic and superconducting properties of both families are governed by their proximity to a quantum critical point (QCP) located inside the superconducting dome. In this review, we critically examine these claims and highlight significant diffe…
The representative cuprate, La$_{2-x}$M$_x$CuO$_4$, with M = Sr and $x = 1/8$ is studied via first-principles calculations in the high-temperature tetragonal (HTT), low-temperature orthorhombic (LTO), and low-temperature less-orthorhombic (LTLO) structures. By suppressing the magnetism and superconductivity, the LTLO phase, which has rarely been observed in La$_{2-x}$Sr$_x$CuO$_4$, is found to be the ground state, where the structural phase transitions, HTT$\rightarrow$LTO$\rightarrow$LTLO, can be understood via phonon instability. While the La-O composition is identified to be responsible for…
Suppression of superconductivity in favour of a striped phase, and its coincidence with a structural transition from a low-temperature orthorhombic (LTO) to a low-temperature tetragonal (LTT) phase, is a ubiquitous feature of hole-doped lanthanum cuprates. We study the effect of anisotropic strain on this transition using density-functional theory on both La$_2$CuO$_4$ and the recently-synthesised surrogate La$_2$MgO$_4$ to decouple electronic and structural effects. Strikingly, we find that compressive strain applied diagonally to the in-plane metal-oxygen bonds dramatically stabilises the LT…
The Seebeck coefficient $S$ of the cuprate YBa$_{2}$Cu$_{3}$O$_{y}$ was measured in magnetic fields large enough to suppress superconductivity, at hole dopings $p = 0.11$ and $p = 0.12$, for heat currents along the $a$ and $b$ directions of the orthorhombic crystal structure. For both directions, $S/T$ decreases and becomes negative at low temperature, a signature that the Fermi surface undergoes a reconstruction due to broken translational symmetry. Above a clear threshold field, a strong new feature appears in $S_{\rm b}$, for conduction along the $b$ axis only. We attribute this feature to …
Magneto-optical signatures of a cascade of transitions in La$_2-x$Ba$_x$CuO$_4$
最近的实验在原来的铜氧化物高温超导体，La $_2-x$ Ba $_x$ CuO $_4$，揭示了一个显着的转变序列[1]。在这里，我们研究了这种晶体的克尔效应，这是敏感的时间反转对称性破缺（TRSB）。并行双折射测量准确地定位从高温四方晶系到低温正交晶系，然后到较低温度四方晶系的结构相变，在该温度下，强克尔信号开始。克尔信号的滞后行为表明，TRSB发生远高于室温，先前在高质量的YBa $_2$ Cu $_3$ O$_{6+x}晶体中观察到的效果[2]。
Fermi Surface Reconstruction and Quantum Oscillations in Underdoped YBa$_2$Cu$_3$O$_{7-x}$ Modeled in a Single Bilayer with Mirror Symmetry Broken by Charge Density Waves
低于最佳掺杂的空穴掺杂高温铜酸盐超导体具有小的类电子费米表面，占据布里渊区的一小部分。有强有力的证据表明，这是链接到电荷密度波（CDW）秩序，重建大的空穴状费米表面预测的能带结构计算。最近的实验已经揭示了在高场量子振荡（QO）测量中的基准双层材料YBa $_2$ Cu $_3$ O $_{7-x}$中的两个CDW组分的结构。我们结合这些结果与紧束缚描述的带在一个孤立的双层给一个极小模型揭示的基本物理的情况。在这里，我们表明，这种方法，结合自旋-轨道相互作用和赝隙的影响，给出了一个很好的定性描述中看到的QO观测在这种材料中的多个频率。通过弱CDW分裂的带的磁击穿将导致QO谱的场依赖性和观察到的四重对称性的结果在倾斜的领域。
Since the discovery of the pseudogap and Fermi arc states in underdoped cuprates, the understanding of such non-Fermi-liquid states and the associated violation of Luttinger's theorem have been the central theme in correlated electron systems. However, still lacking is a well-accepted theoretical framework to unambiguously explain these metallic states that are clearly beyond Landau's Fermi liquid and Luttinger's theorem of a Fermi surface and electron filling. Here, we design a lattice model of orthogonal metals with fermion and Ising matter fields coupled to topological order and, by solving…
本文报道了在欠掺杂铜氧化物超导体YBa $_2$ Cu $_4$ O $_8$（Y 124）中观察到的Shubnikov-de Haas振荡。对于沿c轴排列的场，振荡的频率是$660\pm 30$ T，其对应于第一布里渊区的总面积的$\sim 2.4$ %。这个轨道上准粒子的有效质量被测量为$2.7\pm0.3$乘以自由电子质量。频率和质量都与最近观察到的ortho-II YBa $_2$ Cu $_3$ O $_{6.5}$（Y123-II）相当。我们表明，虽然小费米表面口袋可以预期从能带结构计算在Y123-II，没有这样的口袋预测Y124。因此，我们的研究结果意味着这些小口袋是一个通用的功能的氧化铜平面在欠掺杂的铜酸盐。
We have performed de Haas-van Alphen (dHvA) measurements of the heavy-fermion superconductor CeCoIn$_5$ down to 2 mK above the upper critical field. We find that the dHvA amplitudes show an anomalous suppression, concomitantly with a shift of the dHvA frequency, below the transition temperature $T_{\rm n}=20$ mK. We suggest that the change is owing to magnetic breakdown caused by a field-induced antiferromagnetic (AFM) state emerging below $T_{\rm n}$, revealing the origin of the field-induced quantum critical point (QCP) in CeCoIn$_5$. The field dependence of $T_{\rm n}$ is found to be very w…
