Effect of Anisotropic Hybridization inYbAlB4Probed by Linear Dichroism in Core-Level Hard X-Ray Photoemission Spectroscopy

Abstract

We have probed the crystalline electric-field ground states of pure |J = 7/2, Jz = ±5/2 as well as the anisotropic c-f hybridization in both valence fluctuating systems α-and β-YbAlB4 by linear polarization dependence of angle-resolved core level photoemission spectroscopy. Interestingly, the small but distinct difference between α-and β-YbAlB4 was found in the polar angle dependence of linear dichroism, indicating the difference in the anisotropy of c-f hybridization which may be essential to a heavy Fermi liquid state in α-YbAlB4 and a quantum critical state in β-YbAlB4 .

Strong in-plane anisotropy in the electronic structure of fixed-valence β−LuAlB4

“…As it is isostructural to β-LuAlB 4 , and since the variations in Lu/Yb-B bond lengths are nearly identical (4% in critical β-YbAlB 4 , 5% in non-critical α-YbAlB 4 , and 6% in non-critical β-LuAlB 4 [12]), we would expect that a similar variation of orbital overlap, and thus an anisotropic Kondo hybridization, should prevail in β-YbAlB 4 . Yet, previous studies found an in-plane isotropic Kondo hybridization in αand β-YbAlB 4 [19,20]. Our finding therefore provides evidence that the isotropic Kondo hybridization and intrinsic quantum criticality in β-YbAlB 4 emerge from an anisotropic electronic structure [9,10,16,21].…”

“…This hybridization can induce the observed T /B scaling of the magnetic susceptibility, and can also explain the intrinsic quantum criticality in β-YbAlB 4 [5,[13][14][15][16][17][18]. Recently, strong evidence supporting this in-plane isotropy was found in the linear dichroism of core-level x-ray photoemission and NMR studies [19,20].…”

“…The isomorph α-YbAlB 4 features the same local symmetry and similar valence fluctuations of the Yb atoms, as well as an essentially identical in-plane isotropy of the Kondo hybridization [9,12,19,21]. However, it does not show superconductivity nor intrinsic quantum criticality [12].…”

Charge Transfer Effect under Odd-Parity Crystalline Electric Field

“…In β-YbAlB 4 , the CEF ground state was proposed to be the |J = 7/2, J z = ±5/2 state [11], which has been supported by the measurements of the anisotropy of the magnetic susceptibility [4], the Mössbauer spectroscopy [12] and the linear dichroism in photoemission [13]. This suggests that the CEF is to be understood from the hybridization picture rather than the point-charge model.…”

Ground State Local 4f Symmetry of CeAgSb2 Probed by Linearly Polarized Hard X-ray Photoemission

“…However, it is insensitive for the in-plane rotational symmetry, which is described by the ± sign of the linear combination of the |± 5 2 ⟩ and |± 3 2 ⟩ states, due to the fundamental limitation of the dipole selection rule in the tetragonal systems. This problem has been overcome by the linearly polarized angle-resolved hard X-ray photoemission (HAXPES) with an additional parameter of the detection direction of the photoelectrons [9][10][11][12][13][14]. This technique works to determine the GS symmetry of tetragonal CeCu 2 Ge 2 , which shows an antiferromagnetic order below a Néel temperature (T N ) of 4.15 K at ambient pressure [15], as |Γ 1 7…”