scholarly journals Raman Response of Quantum Critical Ferroelectric Pb-Doped SrTiO3

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1469
Author(s):  
Ekaterina D. Linnik ◽  
Alexey S. Mikheykin ◽  
Diego Rubi ◽  
Vladimir B. Shirokov ◽  
Daoud Mezzane ◽  
...  
Keyword(s):  
Critical Temperature ◽  
Quantum Critical Point ◽  
Tuning Parameter ◽  
Temperature Dependent ◽  
Ferroelectric State ◽  
Ferroelectric Transition ◽  
Close Proximity ◽  
Quantum Critical ◽  
Quantum Phenomena ◽  
Polar Nanoregions

A quantum paraelectric SrTiO3 is a material situated in close proximity to a quantum critical point (QCP) of ferroelectric transition in which the critical temperature to the ferroelectric state is suppressed down to 0 K. However, the understanding of the behavior of the phase transition in the vicinity of this point remains challenging. Using the concentration x of Pb in solid solution Sr1−xPbxTiO3 (PSTx) as a tuning parameter and applying the combination of Raman and dielectric spectroscopy methods, we approach the QCP in PSTx and study the interplay of classical and quantum phenomena in the region of criticality. We obtain the critical temperature of PSTx and the evolution of the temperature-dependent dynamical properties of the system as a function of x to reveal the mechanism of the transition. We show that the ferroelectric transition occurs gradually through the emergence of the polar nanoregions inside the non-polar tetragonal phase with their further expansion on cooling. We also study the ferroelastic cubic-to-tetragonal structural transition, occurring at higher temperatures, and show that its properties are almost concentration-independent and not affected by the quantum criticality.

scholarly journals Bose polarons near quantum criticality

Science ◽  
2020 ◽  
Vol 368 (6487) ◽  
pp. 190-194 ◽  
Author(s):  
Zoe Z. Yan ◽  
Yiqi Ni ◽  
Carsten Robens ◽  
Martin W. Zwierlein
Keyword(s):  
Critical Temperature ◽  
Quantum Critical Point ◽  
Spectral Width ◽  
Quantum Criticality ◽  
Einstein Condensate ◽  
Resonant Interactions ◽  
Bose Einstein Condensate ◽  
Modern Physics ◽  
Quantum Critical ◽  
Bose Einstein

The emergence of quasiparticles in interacting matter represents one of the cornerstones of modern physics. However, in the vicinity of a quantum critical point, the existence of quasiparticles comes under question. Here, we created Bose polarons near quantum criticality by immersing atomic impurities in a Bose-Einstein condensate (BEC) with near-resonant interactions. Using radiofrequency spectroscopy, we probed the energy, spectral width, and short-range correlations of the impurities as a function of temperature. Far below the superfluid critical temperature, the impurities formed well-defined quasiparticles. Their inverse lifetime, given by their spectral width, increased linearly with temperature at the so-called Planckian scale, consistent with quantum critical behavior. Close to the BEC critical temperature, the spectral width exceeded the impurity’s binding energy, signaling a breakdown of the quasiparticle picture.

ANISOTROPIC IN PLAIN Cu-O STRAIN AND THE STRIPE QUANTUM CRITICAL POINT IN YBa2Cu3O6+k

2000 ◽  
Vol 14 (29n31) ◽  
pp. 3668-3672 ◽  
Author(s):  
S. SANNA ◽  
P. MANCA ◽  
S. AGRESTINI ◽  
N. L. SAINI ◽  
A. BIANCONI
Keyword(s):  
Critical Temperature ◽  
Critical Point ◽  
Critical Strain ◽  
Quantum Critical Point ◽  
Temperature Scales ◽  
Quantum Critical

Anisotropic Cu-O strain has been measured and a relation between the superconducting critical temperature and the strain is studied in the YBa 2 Cu 3 O 6+ k (Y123). oxygen ordered YBa 2 Cu 3 O 6+ k phases. We show that the critical temperature scales both with the strain along the a axis (ε a ,) and along the b axis (ε b ). While undoped, the system is close to the critical strain, ε c ~ 0.043. The formation of chains with doping gives rise to a decrease of the ε b to take the system away from the critical point approaching the dynamical quantum stripe fluctuations (ε b <ε c ) and the ε a increases to approach the phase of superconducting stripes (ε a >ε c ).

scholarly journals Nematic quantum criticality in an Fe-based superconductor revealed by strain-tuning

Science ◽  
2021 ◽  
Vol 372 (6545) ◽  
pp. 973-977
Author(s):  
Thanapat Worasaran ◽  
Matthias S. Ikeda ◽  
Johanna C. Palmstrom ◽  
Joshua A. W. Straquadine ◽  
Steven A. Kivelson ◽  
...  
Keyword(s):  
Power Law ◽  
Structural Phase ◽  
Quantum Critical Point ◽  
Quantum Criticality ◽  
Conclusive Evidence ◽  
Tuning Parameter ◽  
Thermodynamic Quantities ◽  
Critical Fluctuations ◽  
Wide Range ◽  
Quantum Critical

Quantum criticality may be essential to understanding a wide range of exotic electronic behavior; however, conclusive evidence of quantum critical fluctuations has been elusive in many materials of current interest. An expected characteristic feature of quantum criticality is power-law behavior of thermodynamic quantities as a function of a nonthermal tuning parameter close to the quantum critical point (QCP). Here, we observed power-law behavior of the critical temperature of the coupled nematic/structural phase transition as a function of uniaxial stress in a representative family of iron-based superconductors, providing direct evidence of quantum critical nematic fluctuations in this material. These quantum critical fluctuations are not confined within a narrow regime around the QCP but rather extend over a wide range of temperatures and compositions.

THE STRAIN QUANTUM CRITICAL POINT FOR SUPERSTRIPES IN THE PHASE DIAGRAM OF ALL CUPRATE PEROVSKITES

2000 ◽  
Vol 14 (29n31) ◽  
pp. 3342-3355 ◽  
Author(s):  
A. BIANCONI ◽  
N. L. SAINI ◽  
S. AGRESTINI ◽  
D. DI CASTRO ◽  
G. BIANCONI
Keyword(s):  
Critical Temperature ◽  
Critical Point ◽  
Quantum Critical Point ◽  
Metallic Phase ◽  
X Ray Diffraction ◽  
Critical Fluctuations ◽  
Local Lattice ◽  
Lattice Distortions ◽  
Quantum Critical ◽  
Function Of Two Variables

The metallic phase in doped cuprate perovskites is determined by both the hope doping δ and the micro-strain ε of the planar Cu-O bond length. The micro-strain ε in the CuO 2 plane has been measured by Cu K-edge EXAFS and x-ray diffraction using synchrotron radiation. The critical micro-strain ε c for the onset of local lattice distortions (LLD) and stripe formation has been determined. The strain quantum critical point (QCP) is found at (ε c ,δ c ). The superconducting critical temperature is measured as a function of two variables T c (ε,δ) and it reaches its maximum at the strain QCP. The superconducting phase occurs in the region of critical fluctuations around this QCP. The critical fluctuations near the strain QCP drives the self-organization of the metallic plane forming a particular superlattice of quantum stripes called "superstripes" that favors the amplification of the superconducting critical temperature.

scholarly journals Tuning the charge density wave quantum critical point and the appearance of superconductivity in TiSe2

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Sangyun Lee ◽  
Tae Beom Park ◽  
Jihyun Kim ◽  
Soon-Gil Jung ◽  
Won Kyung Seong ◽  
...  
Keyword(s):  
Charge Density ◽  
Critical Point ◽  
Charge Density Wave ◽  
Density Wave ◽  
Quantum Critical Point ◽  
Quantum Critical

scholarly journals Lattice-shifted nematic quantum critical point in FeSe1−xSx

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
S. Chibani ◽  
D. Farina ◽  
P. Massat ◽  
M. Cazayous ◽  
A. Sacuto ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Critical Point ◽  
Degrees Of Freedom ◽  
Quantum Critical Point ◽  
Substantial Effect ◽  
Low Energy ◽  
Elastic Coupling ◽  
Superconducting Transition ◽  
Local Moments ◽  
Quantum Critical

AbstractWe report the evolution of nematic fluctuations in FeSe1−xSx single crystals as a function of Sulfur content x across the nematic quantum critical point (QCP) xc ~ 0.17 via Raman scattering. The Raman spectra in the B1g nematic channel consist of two components, but only the low energy one displays clear fingerprints of critical behavior and is attributed to itinerant carriers. Curie–Weiss analysis of the associated nematic susceptibility indicates a substantial effect of nemato-elastic coupling, which shifts the location of the nematic QCP. We argue that this lattice-induced shift likely explains the absence of any enhancement of the superconducting transition temperature at the QCP. The presence of two components in the nematic fluctuations spectrum is attributed to the dual aspect of electronic degrees of freedom in Hund’s metals, with both itinerant carriers and local moments contributing to the nematic susceptibility.

scholarly journals Avoided ferromagnetic quantum critical point in pressurized La5Co2Ge3

2021 ◽  
Vol 103 (5) ◽  
Author(s):  
Li Xiang ◽  
Elena Gati ◽  
Sergey L. Bud'ko ◽  
Scott M. Saunders ◽  
Paul C. Canfield
Keyword(s):  
Critical Point ◽  
Quantum Critical Point ◽  
Quantum Critical
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