scholarly journals Quantum-critical scale invariance in a transition metal alloy

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Yasuyuki Nakajima ◽  
Tristin Metz ◽  
Christopher Eckberg ◽  
Kevin Kirshenbaum ◽  
Alex Hughes ◽  
...  
Keyword(s):  
Scale Invariance ◽  
High Temperature Superconductivity ◽  
Applied Pressure ◽  
Anomalous Behavior ◽  
Zero Field ◽  
Zero Temperature ◽  
Critical System ◽  
Transition Metal Alloy ◽  
Scattering Rate ◽  
Quantum Critical

AbstractQuantum-mechanical fluctuations between competing phases induce exotic collective excitations that exhibit anomalous behavior in transport and thermodynamic properties, and are often intimately linked to the appearance of unconventional Cooper pairing. High-temperature superconductivity, however, makes it difficult to assess the role of quantum-critical fluctuations in shaping anomalous finite-temperature physical properties. Here we report temperature-field scale invariance of non-Fermi liquid thermodynamic, transport, and Hall quantities in a non-superconducting iron-pnictide, Ba(Fe1/3Co1/3Ni1/3)2As2, indicative of quantum criticality at zero temperature and applied magnetic field. Beyond a linear-in-temperature resistivity, the hallmark signature of strong quasiparticle scattering, we find a scattering rate that obeys a universal scaling relation between temperature and applied magnetic fields down to the lowest energy scales. Together with the dominance of hole-like carriers close to the zero-temperature and zero-field limits, the scale invariance, isotropic field response, and lack of applied pressure sensitivity suggests a unique quantum critical system unhindered by a pairing instability.

A METAMAGNETIC QUANTUM CRITICAL ENDPOINT IN Sr3Ru2O7

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3258-3264 ◽  
Author(s):  
S. A. GRIGERA ◽  
A. P. MACKENZIE ◽  
A. J. SCHOFIELD ◽  
S. R. JULIAN ◽  
G. G. LONZARICH
Keyword(s):  
Quantum Critical Point ◽  
Point Of View ◽  
Zero Temperature ◽  
Tuning Parameters ◽  
First Order ◽  
End Point ◽  
Fundamental Point ◽  
New Type ◽  
Quantum Critical ◽  
The Magnetic Field

In this paper, we discuss the concept of a metamagnetic quantum critical end-point, consequence of the depression to zero temperature of a critical end-point terminating a line of first order first transitions. This new type of quantum critical point (QCP) is interesting both from a fundamental point of view: a study of a symmetry conserving QCP, and because it opens the possibility of the use of symmetry breaking tuning parameters, notably the magnetic field. In addition, we discuss the experimental evidence for the existence of such a QCP in the bilayer ruthenate Sr3Ru2O7.

A Crack Close to and Perpendicular to an Interface: Resolution of Anomalous Behavior With a Cohesive Zone

2019 ◽  
Vol 86 (3) ◽  
Author(s):  
George G. Adams
Keyword(s):  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Applied Pressure ◽  
Stress Singularity ◽  
Crack Tip ◽  
Anomalous Behavior ◽  
Work Of Adhesion ◽  
Bimaterial Interface ◽  
Zone Model ◽  
Finite Distance

In this investigation, we consider a crack close to and perpendicular to a bimaterial interface. If the crack tip is at the interface then, depending on material properties, the order of the stress singularity will be equal to, less than, or greater than one-half. However, if the crack tip is located any finite distance away from the interface the stress field is square-root singular. Thus, as the crack tip approaches the interface, the stress intensity factor approaches zero (for cases corresponding to a singularity of order less than one-half) or infinity (for a singularity of order greater than one-half). The implication of this behavior is that for a finite applied pressure the crack will either never reach the interface or will reach the interface with vanishing small applied pressure. In this investigation, a cohesive zone model is used in order to model the crack behavior. It is found that the aforementioned anomalous behavior for the crack without a cohesive zone disappears and that the critical value of the applied pressure for the crack to reach the interface is finite and depends on the maximum stress of the cohesive zone model, as well as on the work of adhesion and the Dundurs' parameters.

DENSITY OF STATES AND ORDER PARAMETER IN DIRTY SUPERCONDUCTORS WITH A WEAKLY BROKEN d-WAVE SYMMETRY

1996 ◽  
Vol 10 (12) ◽  
pp. 537-544 ◽  
Author(s):  
SERGEI V. POKROVSKY
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Density Of States ◽  
Order Parameter ◽  
Zero Temperature ◽  
Scattering Rate ◽  
Wave Symmetry ◽  
Direct Calculations ◽  
D Wave ◽  
Gapless Superconductivity

It is shown by direct calculations that in a superconductor with a slightly violated d-wave symmetry of the order parameter (OP) the impurity driven phase transition from the gapless superconductivity to a state with a finite gap takes place at zero temperature. The corresponding scattering rate is close to the value at which the superconductivity vanishes in the d-superconductor. The behavior of the transition temperature, the OP and the density of states (DOS) is analyzed. The model is plausibly relevant to the BSCCO 2:2:1:2.

Quantum-critical conductivity of the Dirac fluid in graphene

Science ◽  
2019 ◽  
pp. eaat8687 ◽  
Author(s):  
Patrick Gallagher ◽  
Chan-Shan Yang ◽  
Tairu Lyu ◽  
Fanglin Tian ◽  
Rai Kou ◽  
...  
Keyword(s):  
Terahertz Spectroscopy ◽  
Quantum Criticality ◽  
Relativistic Hydrodynamics ◽  
Rapid Rate ◽  
Charge Neutrality ◽  
Scattering Rate ◽  
Rate Characteristic ◽  
Quantum Critical ◽  
On Chip ◽  
Dynamic Excitations

Graphene near charge neutrality is expected to behave like a quantum-critical, relativistic plasma—the “Dirac fluid”—in which massless electrons and holes rapidly collide at a rapid rate. We measure the frequency-dependent optical conductivity of clean, micron-scale graphene at electron temperatures between 77 and 300 K using on-chip terahertz spectroscopy. At charge neutrality, we observe the quantum-critical scattering rate characteristic of the Dirac fluid. At higher doping, we uncover two distinct current-carrying modes with zero and nonzero total momenta, a manifestation of relativistic hydrodynamics. Our work reveals the quantum criticality and unusual dynamic excitations near charge neutrality in graphene.

Crystal Growth, Structure, and Incoherent Metallic Behaviour of FeCrAs

2011 ◽  
Vol 170 ◽  
pp. 276-281 ◽  
Author(s):  
Wen Long Wu ◽  
Alix McCollam ◽  
Ian P. Swainson ◽  
Stephen R. Julian
Keyword(s):  
High Temperature ◽  
High Temperature Superconductivity ◽  
High Temperature Superconductors ◽  
Magnetic Hysteresis ◽  
Freezing Temperature ◽  
Growth Structure ◽  
Preparation Conditions ◽  
Scattering Rate ◽  
Spin Freezing ◽  
Low Levels

There is growing interest in a possible connection between incoherent metallic conduction and high temperature superconductivity, that is exemplified by the behaviour of the parent compounds of the new iron-pnictide high-temperature superconductors. We have recently discovered very incoherent behaviour in the non-superconducting arsenide, FeCrAs. This material shows a non-metallic resistivity that rises with decreasing temperature without saturation or a gap, over three decades of temperature, from 80 mK to 800 K. We briefly review this behaviour, and address the question of disorder: how to test for the presence of disorder in a system where the scattering rate inferred from the resistivity is highly abnormal, and how to produce single crystals with low levels of disorder. Our discussion will focus on magnetic properties. FeCrAs is a partly frustrated magnetic system with a Nèel temperature TN that depends on sample quality, a sample-dependent spin freezing temperature TF < TN, and magnetic hysteresis that depends strongly on preparation conditions due to ferromagnetic minority phases in disordered samples.

Static and dynamic susceptibility in the putative ferromagnetic quantum critical system YbNi4 P2 probed by 31 P NMR

2013 ◽  
Vol 250 (3) ◽  
pp. 519-521 ◽  
Author(s):  
Rajib Sarkar ◽  
Panchanan Khuntia ◽  
Johannes Spehling ◽  
Cornelius Krellner ◽  
Christoph Geibel ◽  
...  
Keyword(s):  
Dynamic Susceptibility ◽  
Critical System ◽  
Quantum Critical

scholarly journals Phase diagram of quantum critical system via local convertibility of ground state

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Si-Yuan Liu ◽  
Quan Quan ◽  
Jin-Jun Chen ◽  
Yu-Ran Zhang ◽  
Wen-Li Yang ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Ground State ◽  
Critical System ◽  
Quantum Critical

DISORDER-INDUCED INSTABILITY OF THE QUANTUM CRITICAL BEHAVIOR OF BOSE FLUIDS

2000 ◽  
Vol 14 (05) ◽  
pp. 173-179
Author(s):  
I. P. TAKOV
Keyword(s):  
Renormalization Group ◽  
Critical Behavior ◽  
Short Range ◽  
Zero Temperature ◽  
Classical Systems ◽  
Renormalization Group Equations ◽  
Quantum Critical ◽  
The One ◽  
Quantum Critical Behavior ◽  
Short Range Correlations

The one-loop renormalization-group equations for Bose fluids with randomly distributed impurities are derived and analyzed with the help of a double ∊-expansion. While the low temperature critical behavior is similar to that of classical systems with extended impurities, the proper quantum critical behavior of disordered Bose fluids at zero temperature is unstable with respect to randomly distributed impurities with short-range correlations.

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