Fig. 3: Electronic correlations in Twisted double bilayer graphene (TDBLG) near charge neutrality point (CNP).
a Power-law fitting of resistance as a function of temperature at different densities. Away from the CNP, at normalized carrier densities n/ns ~ − 0.150, − 0.100, 0.095, the best fit for R = R0 + aTα (R0, a and α respectively are the zero temperature resistance, proportionality constant and exponent) is shown as the blue (red) line at low temperature (high temperature) range. The low temperature exponent shows a clear superlinear behaviour. In contrast near CNP, at n/ns ~ − 0.05, − 0.02, 0.0, 0.02, the resistance shows a sublinear behaviour (blue line is the fit) at low temperature (0.02 − 10 K). The insets show the data in log-log scale. The behaviour of R above 10 K at all density ranges is almost linear with T. b Fitted exponent (α) both for low temperature (<10K) and higher temperature fitting ( > 10K and < 40K) depicted by black circles (with blue error bars) and red circles (with grey error bars) respectively, the error bar represents 95% confidence bound of the fitting for cofficient α, the blue vertical dashed lines frame the region of electron and hole co-existence. The low temperature exponent shows nontrivial sublinearity inside the aforementioned co-existence. c Calculated Fermi surfaces in TDBLG at CNP showing the electron (blue) and the hole (red) pockets. Note that the centres of the pockets are shifted in momentum space (Q1, Q2 and Q3 being the respective shifts). (d) Schematic representation of indirect excitons as pairing between electrons and holes with momentum offset Q0.
