We studied the electronic structure of a Shastry-Sutherland lattice system, HoB${}_4$ employing high-resolution photoemission spectroscopy and ab initio band-structure calculations. The surface and bulk borons exhibit subtle differences and loss of boron compared to the stoichiometric bulk. However, the surface and bulk conduction bands near Fermi level are found to be similar. Evolution of the electronic structure with temperature is found to be similar to that observed in a typical charge-disordered system. A sharp dip is observed at the Fermi level in the low-temperature spectra revealing a signature of antiferromagnetic gap. Asymmetric spectral weight transfer with temperature manifests particle-hole asymmetry that may be related to the exotic properties of these systems.

• Received 17 June 2013

DOI:https://doi.org/10.1103/PhysRevB.88.134405