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تسجيل مستخدم جديدCharge-Transfer Excitations in the Model Superconductor HgBa$_2$CuO$_{bf 4+delta}$
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We report a Cu $K$-edge resonant inelastic x-ray scattering (RIXS) study of charge-transfer excitations in the 2-8 eV range in the structurally simple compound HgBa$_2$CuO$_{4+delta}$ at optimal doping ($T_{rm c} = 96.5 $ K). The spectra exhibit a significant dependence on the incident photon energy which we carefully utilize to resolve a multiplet of weakly-dispersive ($ < 0.5$ eV) electron-hole excitations, including a mode at 2 eV. The observation of this 2 eV excitation suggests the existence of a charge-transfer pseudogap deep in the superconducting phase. Quite generally, our data demonstrate the importance of exploring the incident photon energy dependence of the RIXS cross section.
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The compound HgBa$_2$CuO$_{4+Delta}$ (Hg1201) exhibits a simple tetragonal crystal structure and the highest superconducting transition temperature (T$_c$) among all single Cu-O layer cuprates, with T$_c$ = 97 K (onset) at optimal doping. Due to a la
ck of sizable single crystals, experimental work on this very attractive system has been significantly limited. Thanks to a recent breakthrough in crystal growth, such crystals have now become available. Here, we demonstrate that it is possible to identify suitable heat treatment conditions to systematically and uniformly tune the hole concentration of Hg1201 crystals over a wide range, from very underdoped (T$_c$ = 47 K, hole concentration p ~ 0.08) to overdoped (T$_c$ = 64 K, p ~ 0.22). We then present quantitative magnetic susceptibility and DC charge transport results that reveal the very high-quality nature of the studied crystals. Using XPS on cleaved samples, we furthermore demonstrate that it is possible to obtain large surfaces of good quality. These characterization measurements demonstrate that Hg1201 should be viewed as a model high-temperature superconductor, and they provide the foundation for extensive future experimental work.
We present an inelastic neutron scattering study of the structurally simple single-layer compound HgBa$_2$CuO$_{4+delta}$ close to optimal doping ($T_c approx 96$ K). A well-defined antiferromagnetic resonance with energy $omega_r = 56$ meV ($approx
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The charge-density-wave (CDW) instability in the underdoped, pseudogap part of the cuprate phase diagram has been a major recent research focus, yet measurements of dynamic, energy-resolved CDW correlations are still in their infancy. We report a hig
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