Ultrafast terahertz spectroscopy study of a Kondo insulating thin-film SmB6: Evidence for an emergent surface state

Article

关键词: ELECTRODYNAMICS;    EXCITATIONS;   

DOI  :  10.1103/PhysRevB.97.155119

来源: SCIE

【 摘 要 】

We utilize terahertz time domain spectroscopy to investigate thin films of the heavy fermion compound SmB6, a prototype Kondo insulator. Temperature-dependent terahertz (THz) conductivity measurements reveal a rapid decrease in the Drude weight and carrier scattering rate at similar to T* = 20 K, well below the hybridization gap onset temperature (100 K). Moreover, a low-temperature conductivity plateau (below 20 K) suggests the emergence of a surface state with an effective electron mass of 0.1m(e). The conductivity dynamics following optical excitation is also measured and interpreted using Rothwarf-Taylor (R-T) phenomenology, yielding a hybridization gap energy of 17 meV. However, R-T modeling of the conductivity dynamics reveals a deviation from the expected thermally excited quasiparticle density at temperatures below 20 K, indicative of another channel opening up in the low-energy electrodynamics. Taken together, these results are consistent with the onset of a surface state well below the crossover temperature (100 K) after long-range coherence of the f-electron Kondo lattice is established.

【 授权许可】

Free