We calculate the zero-temperature differential conductance dI/dV of a voltage-biased one-dimensional junction between a nontopological and a topological superconductor for arbitrary junction transparency using the scattering matrix formalism. We consider two representative models for the topological superconductors: (i) spinful p-wave and (ii) s-wave with spin-orbit coupling and spin splitting. We verify that in the tunneling limit (small junction transparencies) where only single Andreev reflections contribute to the current, the conductance for voltages below the nontopological superconductor gap Delta(s) is zero and there are two symmetric conductance peaks appearing at eV = +/-Delta(s). with the quantized value (4-pi)2e(2)/h due to resonant Andreev reflection from the Majorana zero mode. However, when the junction transparency is not small, there is a finite conductance for e vertical bar V vertical bar \< Delta(s) arising from multiple Andreev reflections. The conductance at eV = +/-Delta(s). in this case is no longer quantized. In general, the conductance is particle-hole asymmetric except for sufficiently small transparencies. We further show that, for certain values of parameters, the tunneling conductance from a zero-energy conventional Andreev bound state can be made to mimic the conductance from a true Majorana mode.

}, issn = {2469-9950}, doi = {10.1102/PhysRevB.95.020501}, author = {Setiawan, F. and Cole, William S. and Sau, Jay D. and S. Das Sarma} } @article {ISI:000396095500001, title = {Detecting topological superconductivity using low-frequency doubled Shapiro steps}, journal = {PHYSICAL REVIEW B}, volume = {95}, number = {6}, year = {2017}, month = {FEB 3}, pages = {060501}, abstract = {The fractional Josephson effect has been observed in many instances as a signature of a topological superconducting state containing zero-energy Majorana modes. We present a nontopological scenario which can produce a fractional Josephson effect generically in semiconductor-based Josephson junctions, namely, a resonant impurity bound state weakly coupled to a highly transparent channel. We show that the fractional ac Josephson effect can be generated by the Landau-Zener processes which flip the electron occupancy of the impurity bound state. The Josephson effect signature for Majorana modes become distinct from this nontopological scenario only at low frequency. We prove that a variant of the fractional ac Josephson effect, namely, the low-frequency doubled Shapiro steps, can provide a more reliable signature of the topological superconducting state.}, issn = {2469-9950}, doi = {10.1103/PhysRevB.95.060501}, author = {Sau, Jay D. and Setiawan, F.} } @article { ISI:000416023400007, title = {Electron temperature and tunnel coupling dependence of zero-bias and almost-zero-bias conductance peaks in Majorana nanowires}, journal = {PHYSICAL REVIEW B}, volume = {96}, number = {18}, year = {2017}, month = {NOV 22}, issn = {2469-9950}, doi = {10.1103/PhysRevB.96.184520}, author = {Setiawan, F. and Liu, Chun-Xiao and Sau, Jay D. and S. Das Sarma} } @article { ISI:000408619600008, title = {Phenomenology of the soft gap, zero-bias peak, and zero-mode splitting in ideal Majorana nanowires}, journal = {PHYSICAL REVIEW B}, volume = {96}, number = {5}, year = {2017}, month = {AUG 30}, issn = {2469-9950}, doi = {10.1103/PhysRevB.96.054520}, author = {Liu, Chun-Xiao and Setiawan, F. and Sau, Jay D. and S. Das Sarma} } @article {ISI:000401997600008, title = {Transport in superconductor-normal metal-superconductor tunneling structures: Spinful p-wave and spin-orbit-coupled topological wires}, journal = {PHYSICAL REVIEW B}, volume = {95}, number = {17}, year = {2017}, month = {MAY 22}, pages = {174515}, publisher = {AMER PHYSICAL SOC}, type = {Article}, abstract = {We theoretically study transport properties of voltage-biased one-dimensional superconductor-normal metal-superconductor tunnel junctions with arbitrary junction transparency where the superconductors can have trivial or nontrivial topology. Motivated by recent experimental efforts on Majorana properties of superconductor-semiconductor hybrid systems, we consider two explicit models for topological superconductors: (i) spinful p-wave, and (ii) spin-split spin-orbit-coupled s-wave. We provide a comprehensive analysis of the zero-temperature dc current I and differential conductance dI/dV of voltage-biased junctions with or without Majorana zero modes (MZMs). The presence of an MZM necessarily gives rise to two tunneling conductance peaks at voltages eV = +/-Delta(lead), i.e., the voltage at which the superconducting gap edge of the lead aligns with the MZM. We find that the MZM conductance peak probed by a superconducting lead without a BCS singularity has a nonuniversal value, which decreases with decreasing junction transparency. This is in contrast to the MZM tunneling conductance measured by a superconducting lead with a BCS singularity, where the conductance peak in the tunneling limit takes the quantized value GM = (4 - pi)2e(2)/h independent of the junction transparency. We also discuss the {\textquoteleft}{\textquoteleft}subharmonic gap structure{{\textquoteright}{\textquoteright}}, a consequence of multiple Andreev reflections, in the presence and absence of MZMs. Finally, we show that for finite-energy Andreev bound states (ABSs), the conductance peaks shift away from the gap bias voltage eV = +/-Delta(lead) to a larger value set by the ABSs energy. Our work should have important implications for the extensive current experimental efforts toward creating topological superconductivity and MZMs in semiconductor nanowires proximity coupled to ordinary s-wave superconductors.}, \%\%Address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA

}, issn = {2469-9950}, doi = {10.1103/PhysRevB.95.174515}, author = {Setiawan, F. and Cole, William S. and Sau, Jay D. and S. Das Sarma} } @article { ISI:000411162600002, title = {Transport properties across the many-body localization transition in quasiperiodic and random systems}, journal = {PHYSICAL REVIEW B}, volume = {96}, number = {10}, year = {2017}, month = {SEP 19}, issn = {2469-9950}, doi = {10.1103/PhysRevB.96.104205}, author = {Setiawan, F. and Deng, Dong-Ling and Pixley, J. H.} } @article { ISI:000356473300003, title = {Conductance spectroscopy of topological superconductor wire junctions}, journal = {PHYSICAL REVIEW B}, volume = {91}, number = {21}, year = {2015}, month = {JUN 18}, pages = {214513}, issn = {1098-0121}, doi = {10.1103/PhysRevB.91.214513}, author = {Setiawan, F. and Brydon, P. M. R. and Sau, Jay D. and S. Das Sarma} } @article { ISI:000364024800001, title = {Dynamical Detection of Topological Phase Transitions in Short-Lived Atomic Systems}, journal = {PHYSICAL REVIEW LETTERS}, volume = {115}, number = {19}, year = {2015}, month = {NOV 4}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.115.190401}, author = {Setiawan, F. and Sengupta, K. and Ian B Spielman and Sau, Jay D.} } @article { ISI:000365774000003, title = {Temperature-dependent many-body effects in Dirac-Weyl materials: Interacting compressibility and quasiparticle velocity}, journal = {PHYSICAL REVIEW B}, volume = {92}, number = {23}, year = {2015}, month = {DEC 1}, pages = {235103}, issn = {1098-0121}, doi = {10.1103/PhysRevB.92.235103}, author = {Setiawan, F. and S. Das Sarma} } @article { ISI:000332422500004, title = {Robust two-qubit gates for exchange-coupled qubits}, journal = {PHYSICAL REVIEW B}, volume = {89}, number = {8}, year = {2014}, month = {FEB 28}, pages = {085314}, issn = {1098-0121}, doi = {10.1103/PhysRevB.89.085314}, author = {Setiawan, F. and Hui, Hoi-Yin and J P Kestner and Wang, Xin and S. Das Sarma} }