scholarly journals Fermi Surface with Dirac Fermions in CaFeAsF Determined via Quantum Oscillation Measurements

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Taichi Terashima ◽  
Hishiro T. Hirose ◽  
David Graf ◽  
Yonghui Ma ◽  
Gang Mu ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Quantum Oscillation ◽  
Dirac Fermions

scholarly journals Aspects of quantum information in finite density field theory

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Lucas Daguerre ◽  
Raimel Medina ◽  
Mario Solís ◽  
Gonzalo Torroba
Keyword(s):  
Field Theory ◽  
Quantum Information ◽  
Mutual Information ◽  
Fermi Surface ◽  
Relative Entropy ◽  
Chemical Potential ◽  
Operator Product ◽  
Dirac Fermions ◽  
Long Distance ◽  
Finite Density

Abstract We study different aspects of quantum field theory at finite density using methods from quantum information theory. For simplicity we focus on massive Dirac fermions with nonzero chemical potential, and work in 1 + 1 space-time dimensions. Using the entanglement entropy on an interval, we construct an entropic c-function that is finite. Unlike what happens in Lorentz-invariant theories, this c-function exhibits a strong violation of monotonicity; it also encodes the creation of long-range entanglement from the Fermi surface. Motivated by previous works on lattice models, we next calculate numerically the Renyi entropies and find Friedel-type oscillations; these are understood in terms of a defect operator product expansion. Furthermore, we consider the mutual information as a measure of correlation functions between different regions. Using a long-distance expansion previously developed by Cardy, we argue that the mutual information detects Fermi surface correlations already at leading order in the expansion. We also analyze the relative entropy and its Renyi generalizations in order to distinguish states with different charge and/or mass. In particular, we show that states in different superselection sectors give rise to a super-extensive behavior in the relative entropy. Finally, we discuss possible extensions to interacting theories, and argue for the relevance of some of these measures for probing non-Fermi liquids.

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 ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Quantum Oscillation

Robust Quantum Oscillation of Dirac Fermions in a Single-Defect Resonant Transistor

ACS Nano ◽  
2021 ◽  
Author(s):  
Shoujun Zheng ◽  
Yanggeun Joo ◽  
Mali Zhao ◽  
Kyungrok Kang ◽  
Kenji Watanabe ◽  
...  
Keyword(s):  
Quantum Oscillation ◽  
Dirac Fermions ◽  
Single Defect

Quantum oscillations in the high- T c cuprates

2011 ◽  
Vol 369 (1941) ◽  
pp. 1687-1711 ◽  
Author(s):  
Suchitra E. Sebastian ◽  
Neil Harrison ◽  
Gilbert G. Lonzarich
Keyword(s):  
Fermi Surface ◽  
Cuprate Superconductors ◽  
Low Energy ◽  
Quantum Oscillation ◽  
Electronic Excitations ◽  
Close Correspondence ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Quantum Oscillations ◽  
Underdoped Cuprates

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.

scholarly journals Large nonsaturating magnetoresistance and signature of nondegenerate Dirac nodes in ZrSiS

2017 ◽  
Vol 114 (10) ◽  
pp. 2468-2473 ◽  
Author(s):  
Ratnadwip Singha ◽  
Arnab Kumar Pariari ◽  
Biswarup Satpati ◽  
Prabhat Mandal
Keyword(s):  
Berry Phase ◽  
Large Family ◽  
Chiral Anomaly ◽  
Quantum Oscillation ◽  
Dirac Fermions ◽  
Linear Dispersion ◽  
Large Hole ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Hall Effect Measurements ◽  
The Rich

Whereas the discovery of Dirac- and Weyl-type excitations in electronic systems is a major breakthrough in recent condensed matter physics, finding appropriate materials for fundamental physics and technological applications is an experimental challenge. In all of the reported materials, linear dispersion survives only up to a few hundred millielectronvolts from the Dirac or Weyl nodes. On the other hand, real materials are subject to uncontrolled doping during preparation and thermal effect near room temperature can hinder the rich physics. In ZrSiS, angle-resolved photoemission spectroscopy measurements have shown an unusually robust linear dispersion (up to∼2 eV) with multiple nondegenerate Dirac nodes. In this context, we present the magnetotransport study on ZrSiS crystal, which represents a large family of materials (WHMwithW= Zr, Hf;H= Si, Ge, Sn;M= O, S, Se, Te) with identical band topology. Along with extremely large and nonsaturating magnetoresistance (MR),∼1.4×105% at 2 K and 9 T, it shows strong anisotropy, depending on the direction of the magnetic field. Quantum oscillation and Hall effect measurements have revealed large hole and small electron Fermi pockets. A nontrivialπBerry phase confirms the Dirac fermionic nature for both types of charge carriers. The long-sought relativistic phenomenon of massless Dirac fermions, known as the Adler–Bell–Jackiw chiral anomaly, has also been observed.

scholarly journals Electronic structure of the candidate 2D Dirac semimetal SrMnSb2: a combined experimental and theoretical study

2018 ◽  
Vol 4 (2) ◽  
Author(s):  
Shyama Varier Ramankutty ◽  
Jans Henke ◽  
Adriaan Schiphorst ◽  
Rajah Nutakki ◽  
Stephan Bron ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Fermi Surface ◽  
Theoretical Study ◽  
Berry Phase ◽  
Tight Binding ◽  
Quantum Oscillation ◽  
Great Promise ◽  
Dirac Semimetal ◽  
Arpes Data ◽  
Good Agreement

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.

scholarly journals Accurate determination of the Fermi surface of tetragonal FeS via quantum oscillation measurements and quasiparticle self-consistent GW calculations

2019 ◽  
Vol 99 (13) ◽  
Author(s):  
Taichi Terashima ◽  
Naoki Kikugawa ◽  
David Graf ◽  
Hishiro T. Hirose ◽  
Shinya Uji ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Accurate Determination ◽  
Quantum Oscillation ◽  
Self Consistent

scholarly journals Fragile charge order in the nonsuperconducting ground state of the underdoped high-temperature superconductors

2015 ◽  
Vol 112 (31) ◽  
pp. 9568-9572 ◽  
Author(s):  
B. S. Tan ◽  
N. Harrison ◽  
Z. Zhu ◽  
F. Balakirev ◽  
B. J. Ramshaw ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Fermi Surface ◽  
Copper Oxide ◽  
High Temperature Superconductors ◽  
Field Enhancement ◽  
Charge Order ◽  
Quantum Oscillation ◽  
Oxide Superconductors ◽  
Spectroscopic Techniques ◽  
Copper Oxide Superconductors

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.

scholarly journals Classical Limit for Dirac Fermions with Modified Action in the Presence of a Black Hole

Symmetry ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1294
Author(s):  
Meir Lewkowicz ◽  
Mikhail Zubkov
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Fermi Surface ◽  
Gravitational Collapse ◽  
Classical Limit ◽  
Numerical Solutions ◽  
Equations Of Motion ◽  
Einstein Equations ◽  
Covariant Formulation ◽  
Dirac Fermions

We consider the model of Dirac fermions coupled to gravity as proposed, in which superluminal velocities of particles are admitted. In this model an extra term is added to the conventional Hamiltonian that originates from Planck physics. Due to this term, a closed Fermi surface is formed in equilibrium inside the black hole. In this paper we propose the covariant formulation of this model and analyse its classical limit. We consider the dynamics of gravitational collapse. It appears that the Einstein equations admit a solution identical to that of ordinary general relativity. Next, we consider the motion of particles in the presence of a black hole. Numerical solutions of the equations of motion are found which demonstrate that the particles are able to escape from the black hole.

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