Tunable large spin Hall and spin Nernst effects in the Dirac semimetals ZrXY (X=Si,Ge;Y=S,Se,Te)

Abstract

The ZrSiS-type compounds are Dirac semimetals and thus have been attracting considerable interest in recent years due to their topological electronic properties and possible technological applications. In particular, gapped Dirac nodes can possess large spin Berry curvatures and thus give rise to large spin Hall effect (SHE) and spin Nernst effect (SNE), which may be used to generate pure spin current for spintronics and spin caloritronics without applied magnetic field or magnetic material. In this paper we study both SHE and SNE in ZrXY (X = Si, Ge; Y = S, Se, Te) based on ab initio relativistic band structure calculations. Our theoretical calculations reveal that some of these compounds exhibit large intrinsic spin Hall conductivity (SHC) and spin Nernst conductivity (SNC). For example, the calculated SHC of ZrSiTe is as large as -755 ( /e)(S/cm). Since the electric conductivity of these Dirac semimetals are much smaller than that of platinum which has the largest intrinsic SHC of ∼2200 ( /e)(S/cm), this indicates that they will have a larger spin Hall angle (and hence a more efficient charge-spin current conversion) than that of platinum. Remarkably, we find that both the magnitude and sign of the SHE and SNE in these compounds can be significantly tuned by changing either the electric field direction or spin current direction and may also be optimized by slightly varying the Fermi level via chemical doping. Analysis of the calculated band-and k-resolved spin Berry curvatures show that the large SHE and SNE as well as their remarkable tunabilities originate from the presence of many slightly spin-orbit coupling-gapped Dirac nodal lines near the Fermi level in these Dirac semimetals. Our findings thus suggest that the ZrSiS-type compounds are promising candidates for spintronic and spin caloritronic devices, and will certainly stimulate further experiments on these Dirac semimetals.

Searching for a promising topological Dirac nodal-line semimetal by angle resolved photoemission spectroscopy

“…In addition, ZrGeS owns non-zero Berry phase and Zeeman splitting [19], implying that anomalous Hall effect [44][45][46] may possibly be observed in ZrGeS. Moreover, large spin Hall effect has been reported in ZrGeS [47]. These above together also support that ZrGeS is a kind of promising topological semimetal.…”

Tunable spin-charge conversion in class-I topological Dirac semimetals

“…For both effects, the conversion efficiency is commonly characterized by the spin Hall angle: the ratio of the induced transverse spin (charge) current to the applied charge (spin) current. Following intensive efforts on quantifying the spin Hall angle of transition metals and their alloys 7 , studies have also been extended to explore other materials systems [10][11][12][13][14][15] for more tunable spin-charge conversion, which is potentially useful when it comes to endowing spintronic devices with new functionalities.…”

NMR determination of Van Hove singularity and Lifshitz transitions in nodal-line semimetal ZrSiTe

“…ZrSiTe is distinct among this family since it exhibits a non-symmorphic symmetry-protected nodal line very close to the Fermi energy [12]. Its large region of topologically protected drumhead surface states [13] as well as very large spin Berry curvature and associated spin Hall and Nernst response [14] suggest spintronic and related applications. Suggested changes of Fermi surface topology in this family include a temperature-induced Lifshitz transition in ZrSiSe [15], and a pressure-induced Lifshitz transition in ZrSiTe [16] as well as indications of photo-induced phonon driven transformation [17].…”