Doping Dependence of the Pressure Response of T_c in the SmO_1-xF_xFeAs Superconductors

Abstract

The superconducting transition temperature of the high-Tc SmO1-xFxFeAs superconductors increases monotonically as the F-doping level x increases to 0.20. High-pressure magnetization experiments reveal a strong sensitivity of Tc to interatomic distances in the underdoped regime (x </= 0.12) with the pressure coefficient of Tc, d(ln Tc)/dP being strongly positive. However, as the doping level increases further to x = 0.15, we find that this sensitivity is strongly suppressed and at the same time, d(ln Tc)/dP sharply switches over to assume negative values with Tc decreasing with increasing applied pressure. The abrupt change in the pressure response of the superconducting properties of the SmO1-xFxFeAs phases coincides with the putative existence of a quantum critical point (QCP) near x approximately 0.14, as proposed by resistivity and Hall effect measurements.

Superconductivity under pressure inRFeAsO1−xFx(Miyoshi1, Kojima2, Ogawa3 et al. 2013Phys. Rev. B

“…Pressure dependence of T c has been widely investigated by the ρ(T ) and M(T ) measurements for R = Sm, 15,17,26,28,30 Nd, 14 Pr, 30 and Ce, 16,22,24 and negative pressure coefficients of T c have been found in these studies. In particular, the investigations in the high-pressure range have been done by the ρ(T ) measurements adopting the onset temperature of resistive drop as T c for R = Sm and Nd, resulting in dT c /dP ∼ −3.0 K/GPa.…”

“…The pressure effect for RFeAsO 1−x F x has been investigated by many researchers through the measurements of electrical resistivity (ρ), [12][13][14][15][16][17][18][19][20][22][23][24][25][26] ac and dc magnetization, [27][28][29][30][31] x-ray diffraction, 19,26,32 NMR, 23,33 and others. 20,31 For LaFeAsO 1−x F x with x = 0.11, it has been suggested that T c increases with increasing pressure P and shows a maximum of 43 K at P ∼ 4 GPa through the ρ(T ) measurements by determining T c from the onset of resistive drop.…”

“…However, to our knowledge, the magnetic measurements for RFeAsO 1−x F x have been limited to the low-pressure range below ∼1 GPa. [27][28][29][30][31] In the present work, we have performed dc magnetization measurements for optimum-doped RFeAsO 1−x F x (R = La, Ce-Sm) under pressure using a diamond anvil cell (DAC) to establish the T c -P relation. Our dc magnetic measurement using DAC is a powerful technique to determine T c under pressure and has been successfully applied to other superconductors.…”

Crystal structure and phase transitions across the metal-superconductor boundary in theSmFeAsO1−xFx(Margadonna1, Takabayashi2, McDonald3 et al. 2009Phys. Rev. BSelf Cite127211372View full textAdd to dashboardCite

“…9 The shaded bars near x ~ 0.14 mark the boundary for different behaviour of the temperature-dependent resistivity. …”

First-Principles Study of Hydrogen-Doping Effects on Iron-Based Superconductors

“…Under high pressure, T c of La-1111 increases from 28 K to 40 K, 16) while that of Sm-1111 decreases. 17) The effects of H doping seem to be not effective for optimum iron-based superconductors such as Sm-1111.…”