scholarly journals Quantum oscillation studies of the Fermi surface of LaFePO

2009 ◽  
Vol 469 (9-12) ◽  
pp. 459-468 ◽  
Author(s):  
A. Carrington ◽  
A.I. Coldea ◽  
J.D. Fletcher ◽  
N.E. Hussey ◽  
C.M.J. Andrew ◽  
...  
Author(s):  
Suchitra E. Sebastian ◽  
Neil Harrison ◽  
Gilbert G. Lonzarich

We review recent progress in the study of quantum oscillations as a tool for uniquely probing low-energy electronic excitations in high- T c cuprate superconductors. Quantum oscillations in the underdoped cuprates reveal that a close correspondence with Landau Fermi-liquid behaviour persists in the accessed regions of the phase diagram, where small pockets are observed. Quantum oscillation results are viewed in the context of momentum-resolved probes such as photoemission, and evidence examined from complementary experiments for potential explanations for the transformation from a large Fermi surface into small sections. Indications from quantum oscillation measurements of a low-energy Fermi surface instability at low dopings under the superconducting dome at the metal–insulator transition are reviewed, and potential implications for enhanced superconducting temperatures are discussed.


2018 ◽  
Vol 4 (2) ◽  
Author(s):  
Shyama Varier Ramankutty ◽  
Jans Henke ◽  
Adriaan Schiphorst ◽  
Rajah Nutakki ◽  
Stephan Bron ◽  
...  

SrMnSb_22 is suggested to be a magnetic topological semimetal. It contains square, 2D Sb planes with non-symmorphic crystal symmetries that could protect band crossings, offering the possibility of a quasi-2D, robust Dirac semi-metal in the form of a stable, bulk (3D) crystal. Here, we report a combined and comprehensive experimental and theoretical investigation of the electronic structure of SrMnSb_22, including the first ARPES data on this compound. SrMnSb_22 possesses a small Fermi surface originating from highly 2D, sharp and linearly dispersing bands (the ‘Y-states’) around the (0,/a)-point in kk-space. The ARPES Fermi surface agrees perfectly with that from bulk-sensitive Shubnikov de Haas data from the same crystals, proving the Y-states to be responsible for electrical conductivity in SrMnSb_22. DFT and tight binding (TB) methods are used to model the electronic states, and both show good agreement with the ARPES data. Despite the great promise of the latter, both theory approaches show the Y-states to be gapped above E_FF, suggesting trivial topology. Subsequent analysis within both theory approaches shows the Berry phase to be zero, indicating the non-topological character of the transport in SrMnSb_22, a conclusion backed up by the analysis of the quantum oscillation data from our crystals.


2019 ◽  
Vol 99 (13) ◽  
Author(s):  
Taichi Terashima ◽  
Naoki Kikugawa ◽  
David Graf ◽  
Hishiro T. Hirose ◽  
Shinya Uji ◽  
...  

2015 ◽  
Vol 112 (31) ◽  
pp. 9568-9572 ◽  
Author(s):  
B. S. Tan ◽  
N. Harrison ◽  
Z. Zhu ◽  
F. Balakirev ◽  
B. J. Ramshaw ◽  
...  

The normal state in the hole underdoped copper oxide superconductors has proven to be a source of mystery for decades. The measurement of a small Fermi surface by quantum oscillations on suppression of superconductivity by high applied magnetic fields, together with complementary spectroscopic measurements in the hole underdoped copper oxide superconductors, point to a nodal electron pocket from charge order in YBa2Cu3O6+δ. Here, we report quantum oscillation measurements in the closely related stoichiometric material YBa2Cu4O8, which reveals similar Fermi surface properties to YBa2Cu3O6+δ, despite the nonobservation of charge order signatures in the same spectroscopic techniques, such as X-ray diffraction, that revealed signatures of charge order in YBa2Cu3O6+δ. Fermi surface reconstruction in YBa2Cu4O8 is suggested to occur from magnetic field enhancement of charge order that is rendered fragile in zero magnetic fields because of its potential unconventional nature and/or its occurrence as a subsidiary to more robust underlying electronic correlations.


2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Qing-Ge Mu ◽  
Feng-Ren Fan ◽  
Horst Borrmann ◽  
Walter Schnelle ◽  
Yan Sun ◽  
...  

AbstractWeyl semimetals (WSMs) hosting Weyl points (WPs) with different chiralities attract great interest as an object to study chirality-related physical properties, topological phase transitions, and topological superconductivity. Quantum oscillation measurements and theoretical calculations imply that the type-II WPs in NbIrTe4 are robust against the shift of chemical potential making it a good material for pressure studies on topological properties. Here we report the results of electrical transport property measurements and Raman spectroscopy studies under pressures up to 65.5 GPa accompanied by theoretical electronic structure calculations. Hall resistivity data reveal an electronic transition indicated by a change of the charge carrier from multiband character to hole-type at ~12 GPa, in agreement with the calculated Fermi surface. An onset of superconducting transition is observed at pressures above 39 GPa, with critical temperature increasing as pressure increases. Moreover, theoretical calculations indicate that WPs persist up to highly reduced unit cell volume (−17%), manifesting that NbIrTe4 is a candidate of topological superconductor.


2002 ◽  
Vol 16 (20n22) ◽  
pp. 3004-3007 ◽  
Author(s):  
D. HALL ◽  
T. P. MURPHY ◽  
E. C. PALM ◽  
S. W. TOZER ◽  
Z. FISK ◽  
...  

To understand the electronic structure of the heavy fermion superconductors CeMIn 5, we have performed a comprehensive magnetic study of these materials.1-4 Our quantum oscillation studies reveal that the Fermi surface becomes systematically more 2-d (and displays heavier effective masses) as one progresses from M=Rh to M=Ir to M=Co, consistent with the observed increase in superconducting Tc. Furthermore, dilution studies show that the f-electrons in CeRhIn5 are substantially localized whereas in CeIrIn 5 and CeCoIn 5 a more itinerant character is observed.


2021 ◽  
Vol 6 (1) ◽  
Author(s):  
M. Horio ◽  
Q. Wang ◽  
V. Granata ◽  
K. P. Kramer ◽  
Y. Sassa ◽  
...  

AbstractElectronic band structures in solids stem from a periodic potential reflecting the structure of either the crystal lattice or electronic order. In the stoichiometric ruthenate Ca3Ru2O7, numerous Fermi surface-sensitive probes indicate a low-temperature electronic reconstruction. Yet, the causality and the reconstructed band structure remain unsolved. Here, we show by angle-resolved photoemission spectroscopy, how in Ca3Ru2O7 a C2-symmetric massive Dirac semimetal is realized through a Brillouin-zone preserving electronic reconstruction. This Dirac semimetal emerges in a two-stage transition upon cooling. The Dirac point and band velocities are consistent with constraints set by quantum oscillation, thermodynamic, and transport experiments, suggesting that the complete Fermi surface is resolved. The reconstructed structure—incompatible with translational-symmetry-breaking density waves—serves as an important test for band structure calculations of correlated electron systems.


2019 ◽  
Vol 116 (9) ◽  
pp. 3449-3453 ◽  
Author(s):  
Junfeng He ◽  
Costel R. Rotundu ◽  
Mathias S. Scheurer ◽  
Yu He ◽  
Makoto Hashimoto ◽  
...  

Fermi surface (FS) topology is a fundamental property of metals and superconductors. In electron-doped cuprate Nd2−xCexCuO4 (NCCO), an unexpected FS reconstruction has been observed in optimal- and overdoped regime (x = 0.15–0.17) by quantum oscillation measurements (QOM). This is all the more puzzling because neutron scattering suggests that the antiferromagnetic (AFM) long-range order, which is believed to reconstruct the FS, vanishes before x = 0.14. To reconcile the conflict, a widely discussed external magnetic-field–induced AFM long-range order in QOM explains the FS reconstruction as an extrinsic property. Here, we report angle-resolved photoemission (ARPES) evidence of FS reconstruction in optimal- and overdoped NCCO. The observed FSs are in quantitative agreement with QOM, suggesting an intrinsic FS reconstruction without field. This reconstructed FS, despite its importance as a basis to understand electron-doped cuprates, cannot be explained under the traditional scheme. Furthermore, the energy gap of the reconstruction decreases rapidly near x = 0.17 like an order parameter, echoing the quantum critical doping in transport. The totality of the data points to a mysterious order between x = 0.14 and 0.17, whose appearance favors the FS reconstruction and disappearance defines the quantum critical doping. A recent topological proposal provides an ansatz for its origin.


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