Title: Unconventional Large Linear Magnetoresistance in Cu$_{2-x}$Te,
Abstract: We report a large linear magnetoresistance in Cu$_{2-x}$Te, reaching
$\Delta\rho/\rho(0)$ = 250\% at 2 K in a 9 T field. This is observed for
samples with $x$ in the range 0.13 to 0.22, and the results are comparable to
the effects observed in Ag$_2 X$ materials, although in this case the results
appear for a much wider range of bulk carrier density. Examining the magnitude
vs. crossover field from low-field quadratic to high-field linear behavior, we
show that models based on classical transport behavior best explain the
observed results. The effects are traced to misdirected currents due to
topologically inverted behavior in this system, such that stable surface states
provide the high mobility transport channels. The resistivity also crosses over
to a $T^2$ dependence in the temperature range where the large linear MR
appears, an indicator of electron-electron interaction effects within the
surface states. Thus this is an example of a system in which these interactions
dominate the low-temperature behavior of the surface states.