Physical properties and superconductivity of Heusler compound LiGa2Rh: A first-principles calculation

doi:10.1016/j.ssc.2020.113859

Solid State Communications

Volume 311, May 2020, 113859

https://doi.org/10.1016/j.ssc.2020.113859 Get rights and content

Highlights

•
First-principles method is used to analyze physical properties of LiGa $_{2}$ Rh.
•
The effect of SOC on the physical properties of LiGa $_{2}$ Rh is discussed.
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Our calculations reveal that LiGa $_{2}$ Rh is a phonon-mediated superconductor.
•
The calculated T $_{c}$ of 2.68 K agrees very well with its experimental value of 2.4 K.

Abstract

We have conducted ab initio pseudopotential calculations with and without spin orbit coupling on the physical properties of LiGa $_{2}$ Rh in order to explain the formation of superconductivity. Although the inclusion of spin orbit coupling lifts the degeneracies of electronic bands, its influence remains small near the Fermi level. The elastic calculations reveal that this Heusler superconductor is ductile. Phonon and electron–phonon interaction properties of LiGa $_{2}$ Rh are weakly influenced by the inclusion of spin orbit coupling. An analysis of electron–phonon interaction properties reveals that acoustic phonon branches are more involved in the process of scattering of electrons than optical phonon branches. From the Allen–Dynes modified McMillan formula, the value of superconducting transition temperature is obtained to be 2.68 K which is compatible with the recently reported experimental value of 2.4 K.

Introduction

Heusler compounds are ternary intermetallic compounds of XY $_{2}$ Z, where X and Y denote transition metal atoms and Z stands for a main group element. These compounds have still receiving continuously growing interest [1], [2], [3], [4] because of their diverse properties for optoelectronic [5], [6], [7], shape memory [8], [9], [10], [11] and thermoelectric [12], [13], [14] applications. Furthermore, some Heusler compounds are ferromagnetic with a high Curie temperature and a large magnetization density, and that show some promise for spintronic applications [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27]. The reason for their implementation in spintronic applications is that two spin band exhibit totally varied behavior: the majority of spin band is metallic, whereas the minority spin band displays semiconducting feature. In addition to spintronic, the Heusler family is correlated with the research area of superconductivity. Up to now, there are almost thirty discovered Heusler superconductors [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], [45] with a superconducting transition temperature (T $_{c}$ ) extending from 0.07 K for YPd $_{2}$ Bi [28] to 4.7 K for YPd $_{2}$ Sn [44]. Moreover, coexistence of superconductivity and antiferromagnetic order have been reported for YbPd $_{2}$ Sn and ErPd $_{2}$ Sn [46], [47]. Thus, Heusler compounds pertain to a precious of compounds bridging superconductivity and magnetically ordered compounds.

Theoretical studies on superconductivity of Heusler superconductors are also show interesting features for scientific community. Since YPd $_{2}$ Sn possesses the highest T $_{c}$ value of 4.7 K among Heusler superconductors, ab initio pseudopotential calculations [48] have been conducted on. The most gripping characteristic feature of its phonon dispersion curves has been reported to be the pronounced minimum of transverse acoustic branch (TA) along several symmetry direction. Tütüncü and Srivastava [48] have reported that these phonon anomalies play a noteworthy role in the transition from the nonsuperconducting state to the superconducting state. In addition to YPd $_{2}$ Sn, four more Pd-based Heusler superconductors [41] (ZrPd $_{2}$ Al, HfPd $_{2}$ Al, ZrPd $_{2}$ In, and HfPd $_{2}$ In) have been explored. The T $_{c}$ values of these superconductors [41] range from 2.4 to 3.8 K. An examination of their electronic properties reveals that their electronic structures demonstrate van Hove singularities (saddle points) at the L point [41]. These singularities give rise to a maximum in the corresponding density of states and superconductivity according to the van Hove scenario. Phonon calculations on ZrPd $_{2}$ Al and ZrPd $_{2}$ In indicate that the acoustical modes of ZrPd $_{2}$ Al are unstable close to the $Γ$ point while ZrPd $_{2}$ In is dynamically stable. In agreement with YPd $_{2}$ Sn, phonon anomalies have been observed in the acoustic phonon branches of these two Pd-based Heusler superconductors [41]. A linear response approach on the density functional theory [45] has been used to examine phonon properties of HfPd $_{2}$ Al. Once again, phonon anomalies have been observed in the acoustic phonon branches of this Heusler superconductor [45]. Consequently, Wiendlocha and co-workers [45] have concluded that these phonon anomalies are a common feature of Heusler superconductors since a similar observation has been done for several Heusler superconductors [41], [45], [48].

Recently, the Heusler compound LiGa $_{2}$ Rh has been reported to exhibit a superconducting transition at around 2.4 K [49]. This discovery is interesting because this material is the first Heusler superconductor including lithium. Furthermore, different from most of Heusler superconductors, this material is the main group element-rich (Ga-rich) superconductor rather than the transition metal-rich. Moreover, Carnicom and co-workers [49] have conducted electronic structure calculations on this new Heusler superconductor by using the projector augmented wave (PAW) method. Their calculations [49] reveal that the electronic states near the Fermi level are mainly contributed by Ga 4s, Ga 4p and Rh 4d electrons. In this work, we have analyzed the structural and electronic properties of LiGa $_{2}$ Rh by using the density functional theory with its local density approximation [50], [51]. We have conducted the effective stress–strain calculations in order to designate the single crystal elastic constants of LiGa $_{2}$ Rh. Furthermore, the elastic moduli such as bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio have been derived from the calculated single crystal elastic constants by the help of the Voigt–Reuss–Hill (VRH) approximations [52], [53], [54]. Phonon calculations on LiGa $_{2}$ Rh have been executed by using the density functional perturbation theory within the linear response approach [50], [51]. Finally, the linear response theory [50], [51] and the Migdal–Eliashberg theory [55], [56] are combined to determine the Eliashberg spectral function of LiGa $_{2}$ Rh.

Section snippets

Method

Our calculations have been executed using first principles plane wave pseudopotential method as implemented in the Quantum-Espresso package [50], [51]. The exchange–correlation functional istreated by the local density approximation (LDA) parameterized by Perdew and Zunger [57]. The energy cutoff used for the plane wave expansions is 60 Ryd. Self consistent solutions of the Kohn–Sham equations [58] are achieved by using a set of Monkhorst–Pack special $k$ points [59]. Both scalar and full

Structural, elastic and electronic properties

LiGa $_{2}$ Rh belongs to the face centered cubic L2 $_{1}$ Heusler compounds with the space group Fm $\bar{3}$ m, which has one formula unit in the primitive Bravais cell with Wyckoff positions of atoms at Li (4b) (1/2,1/2,1/2), Ga (8c) (1/4,1/4,1/4) and Rh (4a) (0,0,0), respectively. The cubic L2 $_{1}$ Heusler structure of LiGa $_{2}$ Rh is illustrated in Fig. 1. At the beginning of our calculations, several total energies have been conducted for different volumes around the equilibrium volume V₀. Then, the calculated total

Summary

Firstly, we have viewed the structural and electronic properties of LiGa $_{2}$ Rh with and without SOC by employing the density functional theory with its local density approximation. We have not observed significant changes in the values of lattice parameter ( $a$ ), bulk modulus (B) and its pressure derivative (B $^{'}$ ) with the inclusion of spin orbit coupling. Although the consideration of spin orbit coupling removes the degeneracies of electronic bands at the Fermi level, its impact remains small near

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Cited by (0)

View full text

Physical properties and superconductivity of Heusler compound LiGa2Rh: A first-principles calculation

Highlights

Abstract

Introduction

Section snippets

Method

Structural, elastic and electronic properties

Summary

IUCrJ

IUCrJ

IUCrJ

IUCrJ

Prog. Solid State Chem.

J. Alloys Compd.

J. Alloys Compd.

Solid State Commun.

Mater. Lett.

J. Less-Common Met.

J. Less-Common Met.

J. Magn. Magn. Mater.

Intermetallics

Physica B

Opt. Mater.

J. Phys. Chem. Solids

Semiconductorlike behavior of electrical resistivity in Heusler–Type Fe2VAl Compound

Phys. Rev. Lett.

I–II–V half–Heusler compounds for optoelectronics: Ab initio calculations

Phys. Rev. B

Ultralow thermal conductivity in full Heusler semiconductors

Phys. Rev. Lett.

Magnetic properties and large magnetic-field-induced strains in off-stoichiometric Ni–Mn–Al Heusler alloys

Appl. Phys. Lett.

Martensitic transformation and shape memory effect in ferromagnetic Heusler alloy Ni2FeGa

Appl. Phys. Lett.

Exploring the details of the martensite–austenite phase transition of the shape memory Heusler compound Mn2NiGa by hard x-ray photoelectron spectroscopy, magnetic and transport measurements

Appl. Phys. Lett.

Effect of sb doping on the thermoelectric properties of Ti-based half–Heusler compounds, TiNiSn1−xSbx

Appl. Phys. Lett.

Electronic transport properties of electron– and hole–doped semiconducting C1b Heusler compounds: NiTi1−xMxSn (M=Sc, V)

Phys. Rev. B

New class of materials: half–metallic ferromagnets

Phys. Rev. Lett.

Slater–Pauling behavior and origin of the half–metallicity of the full-Heusler alloys

Phys. Rev. B

Investigation of a novel material for magnetoelectronics: Co2Cr0.6Fe0.4Al

J. Phys.: Condens. Matter

Calculated electronic and magnetic properties of the half–metallic, transition metal based Heusler compounds

J. Phys. D: Appl. Phys.

Spintronics: A challenge for materials science and solidstate chemistry

Angew. Chem. Int. Ed.

Understanding the trend in the Curie temperatures of Co2 –based Heusler compounds: Ab initio calculations

Phys. Rev. B

Spin seebeck effect in thin films of the Heusler compound Co2MnSi

Phys. Rev. B

Direct observation of half–metallicity in the Heusler compound Co2MnSi

Nature Commun.

Future perspectives for spintronic devices

J. Phys. D: Appl. Phys.

Anomalous Hall effect and current spin polarization in Co2FeX Heusler compounds (X= Al, Ga, In, Si, Ge, and Sn): A systematic ab initio study

Phys. Rev. B

Direct evidence for minority spin gap in the Co2MnSi Heusler compound

Phys. Rev. B

Superconductivity in D– and F–Band Metals

Superconductivity of Ni2NbX (X= Al, Ga and Sn)

J. Phys. Soc. Japan

Physical properties and superconductivity of Heusler compound LiGa $_{2}$ Rh: A first-principles calculation

Semiconductorlike behavior of electrical resistivity in Heusler–Type Fe $_{2}$ VAl Compound

Martensitic transformation and shape memory effect in ferromagnetic Heusler alloy Ni $_{2}$ FeGa

Exploring the details of the martensite–austenite phase transition of the shape memory Heusler compound Mn $_{2}$ NiGa by hard x-ray photoelectron spectroscopy, magnetic and transport measurements

Effect of sb doping on the thermoelectric properties of Ti-based half–Heusler compounds, TiNiSn $_{1 - x}$ Sb $_{x}$

Electronic transport properties of electron– and hole–doped semiconducting C1 $_{b}$ Heusler compounds: NiTi $_{1 - x}$ M $_{x}$ Sn (M=Sc, V)

Investigation of a novel material for magnetoelectronics: Co $_{2}$ Cr_0.6Fe_0.4Al

Understanding the trend in the Curie temperatures of Co $_{2}$ $-$ based Heusler compounds: Ab initio calculations

Spin seebeck effect in thin films of the Heusler compound Co $_{2}$ MnSi

Direct observation of half–metallicity in the Heusler compound Co $_{2}$ MnSi

Anomalous Hall effect and current spin polarization in Co $_{2}$ FeX Heusler compounds (X= Al, Ga, In, Si, Ge, and Sn): A systematic ab initio study

Direct evidence for minority spin gap in the Co $_{2}$ MnSi Heusler compound

Superconductivity of Ni $_{2}$ NbX (X= Al, Ga and Sn)