Intrinsic Berry curvature driven anomalous Nernst thermopower in the semimetallic Heusler alloy CoFeVSb

Journal Article · Fri Jun 16 00:00:00 EDT 2023 · Physical Review. B

DOI:https://doi.org/10.1103/physrevb.107.l220403· OSTI ID:2419225

Chanda, Amit ^[1]; Nag, Jadupati ^[2]; Alam, Aftab ^[2]; Suresh, K. G. ^[2]; Phan, Manh-Huong ^[3]; Srikanth, Hariharan ^[3]

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1. Univ. of South Florida, Tampa, FL (United States); OSTI
2. Indian Inst. of Technology (IIT), Mumbai (India)
3. Univ. of South Florida, Tampa, FL (United States)

Understanding of spin-heat coupling mechanisms and magnetothermoelectric phenomena, including the anomalous Nernst effect (ANE), in emergent quaternary Heusler alloys is of practical importance for applications in thermal management and energy harvesting. Here, we demonstrate an intrinsic Berry curvature mediated anomalous Nernst thermopower in CoFeVSb, which orders magnetically at high temperature ( $T_C\approx 850\mathrm{K}$ ) with a large saturation magnetization of $\approx 2.2{\mu }_B/\mathrm{f}.\mathrm{u}.$ at room temperature. We show that the electron-electron elastic and electron-magnon inelastic scattering dominate longitudinal electrical transport at low temperatures ( $T\le 50\mathrm{K}$ ), whereas the electron-phonon and electron-magnon scatterings govern it at higher $T$ . The longitudinal thermopower is resulted mainly from the diffusive contribution with a very large longitudinal Seebeck coefficient ( $42\mu \mathrm{V}{\mathrm{K}}^{-1}$ at 395 K). The value of the anomalous Nernst coefficient ( $S_{\mathrm{ANE}}$ ) for CoFeVSb at room temperature is $0.039\mu \mathrm{V}{\mathrm{K}}^{-1}$ which is higher than the compressively strained $\mathrm{SrRu}{\mathrm{O}}_3$ film ( $0.03\mu \mathrm{V}{\mathrm{K}}^{-1}$ ) as well as the spin gapless semiconductor CoFeCrGa ( $0.018\mu \mathrm{V}{\mathrm{K}}^{-1}$ ). On lowering $T$ , both the ordinary Nernst coefficient and carrier mobility increase but an opposite trend is found for $S_{\mathrm{ANE}}$ . Our ab initio simulations reveal the topological semimetallic nature of CoFeVSb with a pair of Weyl points. These Weyl crossings result in a significant contribution to the Berry curvature, leading to an intrinsic anomalous Hall conductivity ( ${\sigma }_{xy}^{\mathrm{AHE}}$ ) of $\approx 85$ S/cm, which matches well with experiment (77 S/cm at 2 K). Our experimental findings and ab initio calculations support the dominance of the intrinsic Berry curvature in the observed ANE. The ratio of ${\sigma }_{xy}^{\mathrm{AHE}}$ to the transverse anomalous thermoelectric conductivity ( ${\alpha }_{xy}^{\mathrm{ANE}}$ ) shows an increasing trend with $T$ attaining a sizable fraction of $\frac{k_B}{e}\left(\approx 0.35\frac{k_B}{e}\right)$ at room temperature.

• Research Organization: Univ. of South Florida, Tampa, FL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE)
• Grant/Contract Number: FG02-07ER46438
• OSTI ID: 2419225
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 22 Vol. 107; ISSN 2469-9950; ISSN PRBMDO
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Anomalous Hall effect
Fermi surface
Flat bands
Materials Science
Nernst effect
Physics
Spin caloritronics
Spin-orbit coupling
Spintronics
Thermal conductivity
Thermoeletric effects
Thermomagnetic effects