Conductive surface states and Kondo exhaustion in insulating YbIr3Si7
Macy Stavinoha, C.-L. Huang, W. Adam Phelan, Alannah M. Hallas, V. Loganathan, M. Michiardi, J. Falke, Sergey Zhdanovich, D. Takegami, C.-E. Liu, K. D. Tsuei, C. T. Chen, Long Qian, Nicholas J. Ng, Jeffrey W. Lynn, Qingzhen Huang, Franziska Weickert, Vivein Zapf, Katharine R. Larsen, Patricia D. Sparks, James C. Eckert*, Anand B. Puthirath, Hsiang-Hsi Kung, Tor M. Pedersen, Sergey Gorovikov, A. Damascelli, L. H. Tjeng, C. Hooley, Andriy H. Nevidomskyy, and E. Morosan
Conductive surface states and Kondo exhaustion in insulating YbIr3Si7
Physical Review B 109, 035112 (2024)
Abstract
The interplay of Kondo screening and magnetic ordering in strongly correlated materials containing local moments is a subtle problem. Usually the number of conduction electrons per unit cell matches or exceeds the number of moments, and a Kondo-screened heavy Fermi liquid develops at low temperatures. Changing the pressure, magnetic field, or chemical doping can displace this heavy Fermi liquid in favor of a magnetically ordered state. Alternatively, Kondo singlet formation can be suppressed when the number of conduction electrons is small compared to the number of magnetic moments, known as the Kondo exhaustion scenario. Here we report the discovery of such an “exhausted” Kondo lattice material, YbIr3Si7, where the bulk electrical conductivity tends to zero in the antiferromagnetic state below the Néel temperature N=4.1K, as all the free carriers are consumed in the formation of Kondo singlets. By contrast, the surface is conducting, as the Yb3+ ions relax into larger nonmagnetic Yb2+ in the presence of reduced chemical pressure, which shifts the chemical potential.