Electron structure of epitaxial YbSb(001) thin film revealed by ARPES

抄録

Rare-earth mono-pnictides (REPn: RE = rare-earth element, Pn = N, P, As, Sb, and Bi) with the NaCl-type crystal structure have attracted much attention for a long time because of the characteristic magnetic properties originating from the interaction between RE’s localized 4f orbitals and Pn’s p orbitals, namely p-f mixing [1], such as an extreme magnetoresistance (XMR) [2], and complex magnetic phase transitions known as a "devil’s staircase" [3]. Very recently, some of these compounds have also been predicted to be topologically non-trivial due to the band inversion of RE’s d-orbitals and Pn’s p-orbitals at the X point of the bulk Brillouin zone, which has been experimentally demonstrated [4]. This fact makes REPns fertile enough to investigate the interplay between strong electron correlation and topology.

As a member of REPn, in addition to XMR [5], ytterbium mono-antimonide (YbSb) is also expected to be a heavy fermion system with a magnetically ordered ground state [6]. So far, an antiferromagnetic (AFM) ordering at 0.32 K and a mixing-type antiferro-quadrupolar ordering at 30 K in YbSb have been reported with M&oumlssbauer spectroscopy, specific heat measurement, and nuclear magnetic resonance (NMR) using stoichiometric polycrystalline samples [7-9]. However, there is no report on single-crystalline YbSb bulk samples because of the difficulty of the synthesis.

In this work, we fabricated YbSb(001) thin films by co-evaporating Yb and Sb on GaSb(001) substrates using a molecular beam epitaxial method and detected the electronic structure using an angle-resolved photoelectron spectroscopy (ARPES). We monitored the lattice constant during the sample fabrication using a reflection high energy electron diffraction. We confirmed that the fundamental diffraction streaks of the fabricated thin films appeared at the same positions as those of the substrate. This result suggests that the fabricated films have a similar lattice constant to that of GaSb (6.095 Å [10]), which is consistent with the predicted rock salt structure of YbSb (6.081 Å [11]). In the ARPES data of a 14-ML-thickness sample at the temperature of 7.5 K using 21-eV synchrotron light with p-polarization, we observed that the Sb 5p hole band is split into several bands like quantum-well states around the Γ point (Figure 1), as reported in other RESb thin films [12]. These results suggest the successful fabrication of single-crystalline YbSb thin films. In the poster session, we report the sample fabrication details and the observed ARPES data of YbSb.

[1]H Takahashi and T Kasuya, J. Phys. C: Solid State Phys. 18, 2697, 2709, 2721, 2731, 2745, 2755 (1985).

[2] L. Ye et al., PRB 97, 081108 (2018).

[3] T. Chattopadhyay et al., PRB 49, 15096 (1994).

[4] L-L. Wang et al., Commun. Phys. 6, 78 (2023).

[5] W. Xie et al., PRB 101, 085132 (2020).

[6] H. R. Ott et al. Solid State Commun. 55, 113 (1985).

[7] K. Hashi et al., JPSJ. 70, 259 (2001).

[8] A. Oyamada et al., JPSJ. 71, 297 (2002).

[9] A. Yamamoto et al., PRB 70, 220402(R) (2004).

[10] M. E. Straumanis et al., APL 36, 3822 (1965).

[11] J. Hayashi et al., Philo. Mag. 84, 3663 (2004).

[12] S. Chatterjee et al., Sci. Adv. 7, eabe8971 (2021).