Materials Informatics Reveals Unexplored Structure Space in Cuprate Superconductors

欠掺杂铜氧化物中内禀集体模式的关键作用

Crucial role of Internal Collective Modes in Underdoped Cuprates

针对欠掺杂铜氧化物d波超导态的脆弱性问题，结合多种理论方法研究类t-J模型，发现由d波态内禀反对称模式涨落引发的未被探索的不稳定性，结果与相关实验吻合并提出实验方向。

Magnetic field reveals vanishing Hall response in the normal state of stripe-ordered cuprates

The origin of the weak insulating behavior of the resistivity, i.e. $ρ_{xx}\propto\ln(1/T)$, revealed when magnetic fields ($H$) suppress superconductivity in underdoped cuprates has been a longtime mystery. Surprisingly, the high-field behavior of the resistivity observed recently in charge- and spin-stripe-ordered La-214 cuprates suggests a metallic, as opposed to insulating, high-field normal state. Here we report the vanishing of the Hall coefficient in this field-revealed normal state for all $T<(2-6)T_{\mathrm{c}}^{0}$, where $T_{\mathrm{c}}^{0}$ is the zero-field superconducting transit…

Ion-size effects on cuprate High Temperature Superconductors

There are two general ways to compress the cuprates, by external pressure or by internal pressure as induced by isovalent-ion substitution. Paradoxically, they have the opposite effect on the superconducting transition temperature. This thesis seeks to understand the salient difference between these two pressures. We study three families of cuprates where the ion size can be systematically altered; Bi$_2$(Sr$_{1.6-x}$A$_x$)Ln$_{0.4}$CuO$_{6+ δ}$, ACuO$_2 $ and LnBa$_{2-x} $Sr$_x $Cu$_3 $O$_{7-δ} $ where Ln is a Lanthenide or Y and A=\{Mg,Ca,Sr,Ba\}. We use a variety of techniques to explore ou…

Tl2Ba2CuO6+d Brings Spectroscopic Probes Deep Into the Overdoped Regime of the High-Tc Cuprates

Single-particle spectroscopic probes, such as scanning tunneling and angle-resolved photoemission spectroscopy (ARPES), have provided us with crucial insights into the complex electronic structure of the high-Tc cuprates, in particular for the under and optimally doped regimes where high-quality crystals suitable for surface-sensitive experiments are available. Conversely, the elementary excitations on the heavily overdoped side of the phase diagram remain largely unexplored. Important breakthroughs could come from the study of Tl2Ba2CuO6+d (Tl2201), a structurally simple system whose doping l…

2D Ferromagnetism in the High-Tc Analogue Cs_2AgF_4

Although the precise mechanism of high-Tc superconductivity in the layered cuprates remains unknown, it is generally thought that strong 2D Heisenberg antiferromagnetism combined with disruptive hole doping is an essential aspect of the phenomenon. Intensive studies of other layered 3d transition metal systems have greatly extended our understanding of strongly correlated electron states, but to date have failed to show strong 2D antiferromagnetism or high-Tc superconductivity. For this reason the largely unexplored 4d^9 Ag^II fluorides, which are structurally and perhaps magnetically similar …

Disorder-robust phase crystal in high-temperature superconductors stabilized by strong correlations

The simultaneous interplay of strong electron-electron correlations, topological zero-energy states, and disorder is yet an unexplored territory but of immense interest due to their inevitable presence in many materials. Copper oxide high-temperature superconductors (cuprates) with pair breaking edges host a flat band of topological zero-energy states, making them an ideal playground where strong correlations, topology, and disorder are strongly intertwined. Here we show that this interplay in cuprates generates a new phase of matter: a fully gapped ``phase crystal" state that breaks both tran…