Tailoring the nature and strength of electron-phonon interactions in the SrTiO3(001) 2D electron liquid
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Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides1–4. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO3(001) surface5–7 to reveal a remarkably complex evolution of electron–phonon coupling with the tunable carrier density of this system. At low density, where superconductivity is found in the analogous 2DEL at the LaAlO3/SrTiO3 interface8–13, our angle-resolved photoemission data show replica bands separated by 100 meV from the main bands. This is a hallmark of a coherent polaronic liquid and implies long-range coupling to a single longitudinal optical phonon branch. In the overdoped regime the preferential coupling to this branch decreases and the 2DEL undergoes a crossover to a more conventional metallic state with weaker short-range electron–phonon interaction. These results place constraints on the theoretical description of superconductivity and allow a unified understanding of the transport properties in SrTiO3-based 2DELs.
Wang , Z , Walker , S M , Tamai , A , Wang , Y , Ristic , Z , Bruno , F Y , Torre , A D L , Riccò , S , Plumb , N C , Shi , M , Hlawenka , P , Sánchez-Barriga , J , Varykhalov , A , Kim , T K , Hoesch , M , King , P D C , Meevasana , W , Diebold , U , Mesot , J , Moritz , B , Devereaux , T P , Radovic , M & Baumberger , F 2016 , ' Tailoring the nature and strength of electron-phonon interactions in the SrTiO 3 (001) 2D electron liquid ' , Nature Materials , vol. 15 , no. 8 , pp. 835-839 . https://doi.org/10.1038/nmat4623
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