scholarly journals Elastocaloric signature of nematic fluctuations

2021 ◽  
Vol 118 (37) ◽  
pp. e2105911118
Author(s):  
Matthias S. Ikeda ◽  
Thanapat Worasaran ◽  
Elliott W. Rosenberg ◽  
Johanna C. Palmstrom ◽  
Steven A. Kivelson ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Critical Temperature ◽  
Transport Properties ◽  
Order Parameter ◽  
Low Energy ◽  
Elastic Coupling ◽  
Doping Dependence ◽  
Elastocaloric Effect ◽  
Thermodynamic And Transport Properties

The elastocaloric effect (ECE) relates changes in entropy to changes in strain experienced by a material. As such, ECE measurements can provide valuable information about the entropy landscape proximate to strain-tuned phase transitions. For ordered states that break only point symmetries, bilinear coupling of the order parameter with strain implies that the ECE can also provide a window on fluctuations above the critical temperature and hence, in principle, can also provide a thermodynamic measure of the associated susceptibility. To demonstrate this, we use the ECE to sensitively reveal the presence of nematic fluctuations in the archetypal Fe-based superconductor Ba(Fe1−xCox)2As2. By performing these measurements simultaneously with elastoresistivity in a multimodal fashion, we are able to make a direct and unambiguous comparison of these closely related thermodynamic and transport properties, both of which are sensitive to nematic fluctuations. As a result, we have uncovered an unanticipated doping dependence of the nemato-elastic coupling and of the magnitude of the scattering of low-energy quasi-particles by nematic fluctuations—while the former weakens, the latter increases dramatically with increasing doping.

SURFACE EFFECTS ON THE PHASE TRANSITIONS

1992 ◽  
Vol 06 (14) ◽  
pp. 2531-2547 ◽  
Author(s):  
G. BARBERO ◽  
T. BEICA ◽  
R. MOLDOVAN ◽  
A. STEPANESCU
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Surface Tension ◽  
Phase Transitions ◽  
Critical Temperature ◽  
Surface Energy ◽  
Order Parameter ◽  
Multilayer Model ◽  
Classical Models ◽  
New Form

The influence of the surface on the phase transitions is discussed. Classical models are reviewed and critically analyzed. Starting with a multilayer model, a new form of the surface energy is proposed. Our model predicts, contrary to previous models, a surface order parameter different from zero in a temperature range above the critical temperature characterizing the bulk phase transition. The application of the model to the evaluation of the surface tension gives results in agreement with experimental data.

scholarly journals Collective modes in the superfluid inner crust of neutron stars

2015 ◽  
Vol 24 (09) ◽  
pp. 1541006 ◽  
Author(s):  
Michael Urban ◽  
Micaela Oertel
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Transport Properties ◽  
Low Energy ◽  
Collective Modes ◽  
Crystalline Phases ◽  
Long Wavelength ◽  
Thermodynamic And Transport Properties ◽  
Superfluid Hydrodynamics ◽  
Improved Model

The neutron star inner crust is assumed to be superfluid at relevant temperatures. The contribution of neutron quasiparticles to thermodynamic and transport properties of the crust is therefore strongly suppressed by the pairing gap. Nevertheless, the neutron gas still has low-energy excitations, namely long-wavelength collective modes. We summarize different approaches to describe the collective modes in the crystalline phases of the inner crust and present an improved model for the description of the collective modes in the pasta phases within superfluid hydrodynamics.

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.

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