Exploration of strongly correlated states in SmB6 through a comparison of its two-coil pick-up response to that of Bi2Se3
Year: 2023
Type: article
Abstract: Authors of earlier studies on the Kondo insulator ${\mathrm{SmB}}_{6}$ revealed the presence of a bulk Kondo insulating gap between 30 and 50 K and the emergence of a conducting surface state only $<4\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. Here, we compare the two-coil mutual inductance pick-up response of a ${\mathrm{SmB}}_{6}$ single crystal with that of a conventional topological insulator, a ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ single crystal. From these studies, we identify three distinct temperature regimes for ${\mathrm{SmB}}_{6}$, viz., (i) $T\ensuremath{\ge}{T}^{*}$($\ensuremath{\sim}66\phantom{\rule{0.28em}{0ex}}\mathrm{K}$), (ii) ($\ensuremath{\sim}40\phantom{\rule{0.28em}{0ex}}\mathrm{K}$) ${T}_{g}\ensuremath{\le}T<{T}^{*}$, and (iii) $T<{T}_{g}$. At ${T}^{*}$ in ${\mathrm{SmB}}_{6}$, we observe a peak in the temperature-dependent AC pick-up signal which corresponds to the peak in the broad hump feature in the bulk DC susceptibility measurements and features in the resistivity measurements. A dip in the pick-up signal at ${T}_{g}$ in ${\mathrm{SmB}}_{6}$ correlates with the evidence for the opening of a bulk Kondo gap in transport measurements. In this paper on our study of the pick-up signal in ${\mathrm{SmB}}_{6}$, we suggest the presence of a thin (submicron-order thickness), high-conducting surface layer from a temperature just below ${T}_{g}$. In this $T$ regime in ${\mathrm{SmB}}_{6}$, the pick-up signal shows a distinct square root frequency ($\ensuremath{\nu}$) dependence compared with the linear $\ensuremath{\nu}$ dependence found in ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$. Across all the different $T$ regimes, distinct AC frequency dependence and scaling properties are observed. Our results suggest that, above ${T}^{*}$, weak exchange interactions cause electrons to scatter from random ion sites. Electronic correlations gradually strengthen with the onset of Kondo-like hybridization, setting in from below ${T}^{*}$, and at ${T}_{g}$, a strongly correlated Kondo gap opens in the bulk of the material. The appearance of the thin, high-conducting surface layer is nearly coincident with the onset of the bulk Kondo insulating state below ${T}_{g}$ in ${\mathrm{SmB}}_{6}$.
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: Indian Institute of Technology Kanpur, Department of Science and Technology, Ministry of Science and Technology, India, Council of Scientific and Industrial Research, India, Ministry of Education, India, Science and Engineering Research Board, Division of Human Resource Development, Los Alamos National Laboratory
OpenAlex ID: W4388127479