Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userIr 5$d$-band Derived Superconductivity in LaIr$_3$
63
0
0.0
(
0
)
Added by
Amitava Bhattacharyya Dr
Publication date
2019
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We have studied the superconducting properties of LaIr$_3$ with a rhombohedral structure using magnetization, heat capacity, and muon-spin rotation/relaxation ($mu$SR) measurements. The zero-field cooled and field cooled susceptibility measurements exhibit a superconducting transition below $T_{mathrm{C}}$ = 2.5 K. Magnetization measurements indicate bulk type-II superconductivity with upper critical field $mu_0H_{mathrm{c2}}(0)$ = 3.84 T. Two successive transitions are observed in heat capacity data, one at $T_{mathrm{C}}$ = 2.5 K and a second at 1.2 K below $T_{mathrm{C}}$ whose origin remain unclear. The heat capacity jump reveals $Delta C$/$gamma T_{mathrm{C}} sim$ 1.0 which is lower than 1.43 expected for BCS weak coupling limit. Transverse field-$mu$SR measurements reveal a fully gapped $s-$wave superconductivity with 2$Delta(0)/k_{mathrm{B}}T_{mathrm{C}}$ = 3.31, which is small compared to BCS value 3.56, suggesting weak coupling superconductivity. Moreover the study of the temperature dependence of the magnetic penetration depth estimated using the transverse field-$mu$SR measurements gives a zero temperature value of the magnetic penetration depth $lambda_{mathrm{L}}(0)$ = 386(3) nm, superconducting carrier density $n_{mathrm{s}}$ = 2.9(1) $times$10$^{27}$ carriers $m^{-3}$ and the carriers effective-mass enhancement $m^{*}$ = 1.53(1) $m_{mathrm{e}}$. Our zero-field-$mu$SR measurements do not reveal the spontaneous appearance of an internal magnetic field below the transition temperature, which indicates that time-reversal symmetry is preserved in the superconducting state of LaIr$_3$.
rate research
Read More
The electronic properties of the heavy metal superconductor LaIr3 are reported. The estimated superconducting parameters obtained from physical properties measurements indicate that LaIr3 is a BCS-type superconductor. Electronic band structure calculations show that Ir d- states dominate the Fermi level. A comparison of electronic band structures of LaIr3 and LaRh3 shows that the Ir-compound has a strong spin-orbit-coupling effect, which creates a complex Fermi surface.
Polycrystalline sample of superconducting ThIr$_{3}$ was obtained by arc-melting Th and Ir metals. Powder x-ray diffraction revealed that the compound crystalizes in a rhombohedral crystal structure (R-3m, s.g. no. 166) with the lattice parameters: a = 5.3394(1) $r{A}$ and c = 26.4228(8) $r{A}$. Normal and superconducting states were studied by magnetic susceptibility, electrical resistivity and heat capacity measurements. The results showed that ThIr$_{3}$ is a type II superconductor (Ginzburg-Landau parameter $kappa$ = 38) with the critical temperature T$_{c}$ = 4.41 K. The heat capacity data yielded the Sommerfeld coefficient $gamma$ = 17.6 mJ mol$^{-1}$ K$^{-2}$ and the Debye temperature $Theta_{D}$ = 169 K. The ratio $Delta$C / ($gamma$ T$_{c}$) = 1.6, where $Delta$C stands for the specific heat jump at T$_{c}$, and the electron-phonon coupling constant $lambda_{e-p}$ = 0.74 suggest that ThIr$_{3}$ is a moderate-strength superconductor. The experimental studies were supplemented by band structure calculations, which indicated that the superconductivity in ThIr$_{3}$ is governed mainly by 5d states of iridium. The significantly smaller band-structure value of Sommerfeld coefficient as well as the experimentally observed quadratic temperature dependence of resistivity and enhanced magnetic susceptibility suggest presence of electronic interactions in the system, which compete with superconductivity.
Superconductivity in noncentrosymmetric compounds has attracted sustained interest in the last decades. Here we present a detailed study on the transport, thermodynamic properties and the band structure of the noncentrosymmetric superconductor La$_7$Ir$_3$ ($T_c$ $sim$2.3 K) that was recently proposed to break the time-reversal symmetry. It is found that La$_7$Ir$_3$ displays a moderately large electronic heat capacity (Sommerfeld coefficient $gamma_n$ $sim$ 53.1 mJ/mol $text{K}^2$) and a significantly enhanced Kadowaki-Woods ratio (KWR $sim$ 32 $muOmega$ cm mol$^2$ K$^2$ J$^{-2}$) that is greater than the typical value ($sim$ 10 $muOmega$ cm mol$^2$ K$^2$ J$^{-2}$) for strongly correlated electron systems. The upper critical field $H_{c2}$ was seen to be nicely described by the single-band Werthamer-Helfand-Hohenberg model down to very low temperatures. The hydrostatic pressure effects on the superconductivity were also investigated. The heat capacity below $T_c$ reveals a dominant s-wave gap with the magnitude close to the BCS value. The first-principles calculations yield the electron-phonon coupling constant $lambda$ = 0.81 and the logarithmically averaged frequency $omega_{ln}$ = 78.5 K, resulting in a theoretical $T_c$ = 2.5 K, close to the experimental value. Our calculations suggest that the enhanced electronic heat capacity is more likely due to electron-phonon coupling, rather than the electron-electron correlation effects. Collectively, these results place severe constraints on any theory of exotic superconductivity in this system.
We measured the pressure dependence of in-plane resistivity $rho_{ab}$ in the recently-discovered iron-based superconductor Ca$_{10}$(Ir$_{4}$As$_{8}$)(Fe$_{2-x}$Ir$_{x}$As$_{2}$)$_{5}$, which shows a unique structural phase transition in the absence of magnetic ordering, with a superconducting transition temperature $T_{rm c}$ = 16 K and structural phase transition temperature $T_{rm s}$ $simeq$ 100 K at ambient pressure. $T_{rm c}$ and $T_{rm s}$ are suppressed on applying pressure and disappear at approximately 0.5 GPa, suggesting a relationship between superconductivity and structure. Ca$_{10}$(Ir$_{4}$As$_{8}$)(Fe$_{2-x}$Ir$_{x}$As$_{2}$)$_{5}$ is a rather rare example in which the superconductivity appears only in a low-temperature ordered phase. The fact that the change in the crystal structure is directly linked with superconductivity suggests that the crystal structure as well as magnetism are important factors governing superconductivity in iron pnictides.
The rich phase diagram of the two dimensional electron gas (2DEG) at the STO/LAO interface is probed using Hall and longitudinal resistivity. Thanks to a special bridge design we are able to tune through the superconducting transition temperature T$_c$ and to mute superconductivity by either adding or removing carriers in a gate bias range of a few volts. Hall signal measurements pinpoint the onset of population of a second mobile band right at the carrier concentration where maximum superconducting T$_c$ and critical field H$_c$ occur. These results emphasize the advantages of our design, which can be applied to many other two dimensional systems assembled on top of a dielectric substrate with high permittivity.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
