TY - JOUR
T1 - Cascades between Light and Heavy Fermions in the Normal State of Magic-Angle Twisted Bilayer Graphene
AU - Kang, Jian
AU - Bernevig, B. Andrei
AU - Vafek, Oskar
N1 - Funding Information:
J. K. acknowledges the support from the NSFC Grant No. 12074276, and the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions. B. A. B. is supported by the ONR No. N00014-20-1-2303 and partially by DOE Grant No. DE-SC0016239, NSF- MRSEC No. DMR-1420541 and No. DMR-2011750. O. V. is supported by NSF DMR-1916958 and partially by the National High Magnetic Field Laboratory through NSF Grant No. DMR-1157490 and the State of Florida. This research was facilitated by the KITP program “Correlated Systems with Multicomponent Local Hilbert Spaces,” supported in part by the National Science Foundation under Grant No. NSF PHY-1748958.
Publisher Copyright:
© 2021 American Physical Society.
PY - 2021/12/24
Y1 - 2021/12/24
N2 - We present a framework for understanding the cascade transitions and the Landau level degeneracies of twisted bilayer graphene. The Coulomb interaction projected onto narrow bands causes the charged excitations at an integer filling to disperse, forming new bands. If the excitation moves the filling away from the charge neutrality point, then it has a band minimum at the moiré Brillouin zone center with a small mass that compares well with the experiment; if towards the charge neutrality point, then it has a much larger mass and a higher degeneracy. At a nonzero density away from an integer filling the excitations interact. The system on the small mass side has a large bandwidth and forms a Fermi liquid. On the large mass side the bandwidth is narrow, the compressibility is negative and the Fermi liquid is likely unstable. This explains the observed sawtooth features in compressibility, the Landau fans pointing away from charge neutrality and their degeneracies. The framework sets the stage for superconductivity at lower temperatures.
AB - We present a framework for understanding the cascade transitions and the Landau level degeneracies of twisted bilayer graphene. The Coulomb interaction projected onto narrow bands causes the charged excitations at an integer filling to disperse, forming new bands. If the excitation moves the filling away from the charge neutrality point, then it has a band minimum at the moiré Brillouin zone center with a small mass that compares well with the experiment; if towards the charge neutrality point, then it has a much larger mass and a higher degeneracy. At a nonzero density away from an integer filling the excitations interact. The system on the small mass side has a large bandwidth and forms a Fermi liquid. On the large mass side the bandwidth is narrow, the compressibility is negative and the Fermi liquid is likely unstable. This explains the observed sawtooth features in compressibility, the Landau fans pointing away from charge neutrality and their degeneracies. The framework sets the stage for superconductivity at lower temperatures.
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U2 - 10.1103/PhysRevLett.127.266402
DO - 10.1103/PhysRevLett.127.266402
M3 - Article
C2 - 35029496
AN - SCOPUS:85122054333
SN - 0031-9007
VL - 127
JO - Physical review letters
JF - Physical review letters
IS - 26
M1 - 266402
ER -