scholarly journals Спектры пропускания монокристаллов гибридных перовскитов MAPbI-=SUB=-3-=/SUB=- вблизи края фундаментального поглощения

2022 ◽  
Vol 130 (1) ◽  
pp. 116
Author(s):  
В.Е. Аникеева ◽  
К.Н. Болдырев ◽  
О.И. Семенова ◽  
М.Н. Попова
Keyword(s):  
Phase Transition ◽  
Absorption Edge ◽  
Structural Phase ◽  
Fundamental Absorption Edge ◽  
Orthorhombic Phase ◽  
Temperature Hysteresis ◽  
First Order ◽  
Hybrid Perovskite ◽  
First Order Phase Transition ◽  
First Order Phase

The paper presents the transmission spectra of hybrid perovskite MAPbI3 single crystals near the fundamental absorption edge in a wide temperature range. The absorption coefficient α of the single crystal samples is estimated at a temperature T = 150 K for the light with a photon energy E = 1.6 eV and at T = 40 K for E = 1.8 eV. The obtained values turned out to be several orders of magnitude smaller than the values of α for thin-film samples known from the literature. A sharp shift of the fundamental absorption edge by ~ 100 meV was observed at a temperature T1 = 160 K of the structural phase transition from the tetragonal to the orthorhombic phase. The temperature hysteresis of the shift of the fundamental absorption edge near T1 was recorded, which is characteristic of a first-order phase transition.

scholarly journals Structures, Phase Transitions and Tricritical Behavior of the Hybrid Perovskite Methyl Ammonium Lead Iodide

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
P. S. Whitfield ◽  
N. Herron ◽  
W. E. Guise ◽  
K. Page ◽  
Y. Q. Cheng ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Structural Phase ◽  
Photovoltaic Performance ◽  
Orthorhombic Phase ◽  
Structural Phase Transitions ◽  
Lead Iodide ◽  
First Order ◽  
Hybrid Perovskite ◽  
The Impact

Abstract We have examined the crystal structures and structural phase transitions of the deuterated, partially deuterated and hydrogenous organic-inorganic hybrid perovskite methyl ammonium lead iodide (MAPbI3) using time-of-flight neutron and synchrotron X-ray powder diffraction. Near 330 K the high temperature cubic phases transformed to a body-centered tetragonal phase. The variation of the order parameter Q for this transition scaled with temperature T as Q ∼ (Tc−T)β, where Tc is the critical temperature and the exponent β was close to ¼, as predicted for a tricritical phase transition. However, we also observed coexistence of the cubic and tetragonal phases over a range of temperature in all cases, demonstrating that the phase transition was in fact first-order, although still very close to tricritical. Upon cooling further, all the tetragonal phases transformed into a low temperature orthorhombic phase around 160 K, again via a first-order phase transition. Based upon these results, we discuss the impact of the structural phase transitions upon photovoltaic performance of MAPbI3 based solar cells.

Structural phase transition of CeAuGe at high pressure

2005 ◽  
Vol 220 (2/3) ◽  
Author(s):  
Valeri Brouskov ◽  
Michael Hanfland ◽  
Rainer Pöttgen ◽  
Ulrich Schwarz
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Structural Phase ◽  
Lattice Parameter ◽  
First Order ◽  
First Order Phase Transition ◽  
Diamond Anvil ◽  
Ternary Intermetallic Compound ◽  
First Order Phase ◽  
Type Crystal

AbstractStructural properties of the ternary intermetallic compound CeAuGe were investigated at hydrostatic pressures up to 15 GPa with high-resolution angle dispersive X-ray powder diffraction using synchrotron radiation and the diamond anvil cell technique. At 8.7(7) GPa a first order phase transition is observed from a hexagonal NdPtSb-type arrangement into an orthorhombic high-pressure modification with a TiNiSi-type crystal structure. The transformation is associated with a 3% shortening of the lattice parameter perpendicular to the puckered layers [AuGe]

scholarly journals Gravitational wave signals of dark matter freeze-out

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Danny Marfatia ◽  
Po-Yan Tseng
Keyword(s):  
Phase Transition ◽  
Dark Matter ◽  
Gravitational Waves ◽  
Order Phase Transition ◽  
First Order ◽  
Stochastic Background ◽  
First Order Phase Transition ◽  
Relic Abundance ◽  
First Order Phase ◽  
Freeze Out

Abstract We study the stochastic background of gravitational waves which accompany the sudden freeze-out of dark matter triggered by a cosmological first order phase transition that endows dark matter with mass. We consider models that produce the measured dark matter relic abundance via (1) bubble filtering, and (2) inflation and reheating, and show that gravitational waves from these mechanisms are detectable at future interferometers.

scholarly journals Dark Matter production from relativistic bubble walls

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Aleksandr Azatov ◽  
Miguel Vanvlasselaer ◽  
Wen Yin
Keyword(s):  
Phase Transition ◽  
Dark Matter ◽  
Electroweak Phase Transition ◽  
First Order ◽  
Matter Production ◽  
First Order Phase Transition ◽  
Relic Abundance ◽  
Higgs Portal ◽  
First Order Phase ◽  
Gravitational Background

Abstract In this paper we present a novel mechanism for producing the observed Dark Matter (DM) relic abundance during the First Order Phase Transition (FOPT) in the early universe. We show that the bubble expansion with ultra-relativistic velocities can lead to the abundance of DM particles with masses much larger than the scale of the transition. We study this non-thermal production mechanism in the context of a generic phase transition and the electroweak phase transition. The application of the mechanism to the Higgs portal DM as well as the signal in the Stochastic Gravitational Background are discussed.

Discovering a First-Order Phase Transition in the Li–CeO2 System

Nano Letters ◽  
2017 ◽  
Vol 17 (2) ◽  
pp. 1282-1288 ◽  
Author(s):  
Kaikai Li ◽  
Xiaoye Zhou ◽  
Anmin Nie ◽  
Sheng Sun ◽  
Yan-Bing He ◽  
...  
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase
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