Fermi-surface studies of altermagnetic CrSb from Shubnikov-de Haas oscillations

Abstract

Within the family of altermagnets, CrSb is a metallic, collinearly ordered material that exhibits particularly strong symmetry-induced spin splitting in its band structure. In this study, we combine electrical magnetotransport measurements up to 68 T on microfabricated single-crystalline CrSb with first-principles calculations to investigate its Fermi surface. Notably, we study the temperature and field-orientation dependence of magnetic quantum oscillations observed in the magnetoresistance. The observed frequency spectrum agrees well with results from density-functional-theory calculations. Our results confirm the predicted electronic band structure of altermagnetic CrSb and highlight the importance of high magnetic fields for accurately mapping the Fermi surfaces of unconventional emergent materials.

Figures (12)

• Figure 1: Field dependence of the longitudinal resistance of sample L1$a'$ up to 67 T for selected temperatures. Upper inset: False-color SEM image of the microstructure L1$a'$ with current applied along $a'$ axis and voltage measured between $V_1$ and $V_2$. Purple shaded regions indicate bulk CrSb, while yellow shaded regions represent sputtered gold contacts. Lower inset: Zoom-in with curves shifted by a constant offset of $0.1\,\Omega$. Slow variations are SdH oscillations.
• Figure 2: (a) Selected residual-resistance curves for L1$a'$ after subtraction of a third-degree polynomial for different temperatures plotted against inverse magnetic field aligned along $c$. (b) FFT spectra of the data in (a) for a field window between 40 and 66.6 T. (c) Temperature dependence of the FFT amplitude for the frequency $F_1$. The dashed curve is a fit using the LK thermal damping factor.
• Figure 3: (a) Magnetoresistance of L1$a'$ recorded at 4.2 K after background subtraction (third-degree polynomial) for various fixed polar angles $\theta$ within the $a'-c$ plane. (b) Respective FFT spectra for selected angles. The inset shows a contour plot of the FFT amplitudes. (c) Angle-dependent FFT amplitude for the peak in the FFT spectrum for rotations in the $a'-c$ and $a-c$ plane. Dashed lines are guides to the eye using a basis spline in order to highlight the oscillating nature of the MQO amplitude depending on the tilt angle.
• Figure 4: (a) Magnetoresistance of sample L3$c$ after background subtraction of a third-degree polynomial for selected polar angles $\theta$ within the $a-c$ plane. (b) FFT spectra shifted consecutively by a constant offset. We chose a field window between 40 and 61.7 T.
• Figure 5: (a) Crystal structure of Cr Sb (b) Sketch of the first Brillouin zone and high-symmetry points. (c) Altermagnetic band structure of CrSb including SOC using VASP. (d)-(g) Calculated FSs in the first Brillouin zone, where $+$ and $-$ indicate the band shifts with respect to the internal field from SOC. Purple- and cyan-shaded areas mark the local spin polarization $S_z$ along the $c$ axis.