Fractional topological states of dipolar fermions in one-dimensional optical superlattices

We study the properties of dipolar fermions trapped in one-dimensional bichromatic optical lattices and show the existence of fractional topological states in the presence of strong dipole-dipole interactions. We find some interesting connections between fractional topological states in one-dimensional superlattices and the fractional quantum Hall states: (i) the one-dimensional fractional topological states for systems at filling factor \nu=1/p have p-fold degeneracy, (ii) the quasihole excitations fulfill the same counting rule as that of fractional quantum Hall states, and (iii) the total Chern number of p-fold degenerate states is a nonzero integer. The existence of crystalline order in our system is also consistent with the thin-torus limit of the fractional quantum Hall state on a torus. The possible experimental realization in cold atomic systems offers a new platform for the study of fractional topological phases in one-dimensional superlattice systems.Comment: 5+5 pages, 5+3 figures, version appeared in PRL, supplemental material include

Measurement of Absorption Cross Section of a Lossy Object in Reverberation Chamber Without the Need for Calibration

A reliable and simple procedure is proposed to measure the averaged absorption cross section (ACS) of a lossy object in a reverberation chamber (RC). This procedure is based on the time-domain measurement of the ACS in an RC. In the time-domain, to obtain the ACS, the chamber decay time needs to be known. Conventionally, the ACS is normally measured in the frequency domain, and a full two-port calibration must be carried out before collecting the S-parameters, which is tedious and time-consuming. In reality, the chamber decay time depends on the diffused loss of the RC, not the insertion loss of the cables. In this paper, by making use of this fact, the ACS can be measured accurately without calibration, which will simplify the measurement process and shorten the measurement time at the same time