Austin Marga; Venkat Chandrasekhar
Using Crossed Andreev Reflection to Split Electrons Unpublished
2025.
Abstract | Links | BibTeX | Tags: crossed andreev reflection, phase coherence, Proximity effect, Superconductivity
@unpublished{Marga2025,
title = {Using Crossed Andreev Reflection to Split Electrons},
author = {Austin Marga and Venkat Chandrasekhar},
url = {https://doi.org/10.48550/arXiv.2510.25641
},
year = {2025},
date = {2025-10-29},
urldate = {2025-10-29},
abstract = {Mesoscopic systems possess shot noise in their currents due to the quantization of the conducting quasiparticles. Measurements of this shot noise are useful to study phenomena that do not manifest themselves in standard conductance or resistance measurements, such as the statistics of the conducting quasiparticles or quantum entanglement via Bell tests. The corresponding particle statistics can be determined via two particle quantum interference experiments, such as the Hong-Ou-Mandel effect which demonstrates a bunching effect for bosons or an anti-bunching effect in fermions. In superconducting proximity junctions, electrons incident on a superconductor can induce holes via crossed Andreev reflection (CAR) in spatially separated normal metal leads, where the resulting hole currents have nontrivial partition noise due to the four terminal configuration. These nonlocally generated currents, using a superconductor as a mesoscopic beam splitter, enable fabrication of mesoscopic analogs to quantum optics interferometers using metallic and superconducting films with multiport geometries.},
keywords = {crossed andreev reflection, phase coherence, Proximity effect, Superconductivity},
pubstate = {published},
tppubtype = {unpublished}
}
Mesoscopic systems possess shot noise in their currents due to the quantization of the conducting quasiparticles. Measurements of this shot noise are useful to study phenomena that do not manifest themselves in standard conductance or resistance measurements, such as the statistics of the conducting quasiparticles or quantum entanglement via Bell tests. The corresponding particle statistics can be determined via two particle quantum interference experiments, such as the Hong-Ou-Mandel effect which demonstrates a bunching effect for bosons or an anti-bunching effect in fermions. In superconducting proximity junctions, electrons incident on a superconductor can induce holes via crossed Andreev reflection (CAR) in spatially separated normal metal leads, where the resulting hole currents have nontrivial partition noise due to the four terminal configuration. These nonlocally generated currents, using a superconductor as a mesoscopic beam splitter, enable fabrication of mesoscopic analogs to quantum optics interferometers using metallic and superconducting films with multiport geometries.
Venkat Chandrasekhar
Tuning the fundamental periodicity of the current-phase relation in multiterminal diffusive Josephson junctions Journal Article
In: Physical Review B, vol. 112, pp. 104508, 2025.
Abstract | Links | BibTeX | Tags: phase coherence, Proximity effect, Superconductivity
@article{Chandrasekhar2025,
title = {Tuning the fundamental periodicity of the current-phase relation in multiterminal diffusive Josephson junctions},
author = {Venkat Chandrasekhar},
url = {https://journals.aps.org/prb/abstract/10.1103/73rl-wmzw},
year = {2025},
date = {2025-09-18},
urldate = {2025-09-18},
journal = {Physical Review B},
volume = {112},
pages = {104508},
abstract = {Conventional superconductor/insulator/superconductor (SIS) Josephson junctions, devices where two superconductors are separated by a tunnel barrier are technologically important as elements in quantum circuits, particularly with their key role in superconducting qubits. An important characteristic of Josephson junctions is the relation between the supercurrent Is and the phase difference ϕ between them. For SIS junctions, the current-phase relation is sinusioidal and 2π periodic. Other types of Josephson junctions, where the material between the superconductors is a weak link or a normal metal (N) may have non-sinusoidal current-phase relations that are still 2π periodic. We show here that a multi-terminal diffusive SNS Josephson junction with 4 superconducting contacts can show a current phase relation between two of the contacts that is a superposition of 2π and 4π periodic components whose relative strength is controlled by the phase difference between the other two contacts, becoming 2π or 4π periodic for certain values of this phase difference. This tunability might have applications in tailoring the Hamiltonians of superconducting quantum circuits.},
keywords = {phase coherence, Proximity effect, Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Conventional superconductor/insulator/superconductor (SIS) Josephson junctions, devices where two superconductors are separated by a tunnel barrier are technologically important as elements in quantum circuits, particularly with their key role in superconducting qubits. An important characteristic of Josephson junctions is the relation between the supercurrent Is and the phase difference ϕ between them. For SIS junctions, the current-phase relation is sinusioidal and 2π periodic. Other types of Josephson junctions, where the material between the superconductors is a weak link or a normal metal (N) may have non-sinusoidal current-phase relations that are still 2π periodic. We show here that a multi-terminal diffusive SNS Josephson junction with 4 superconducting contacts can show a current phase relation between two of the contacts that is a superposition of 2π and 4π periodic components whose relative strength is controlled by the phase difference between the other two contacts, becoming 2π or 4π periodic for certain values of this phase difference. This tunability might have applications in tailoring the Hamiltonians of superconducting quantum circuits.
Venkat Chandrasekhar
Probing the topological band structure of diffusive multiterminal Josephson junction devices with conductance measurements Journal Article
In: Applied Physics Letters, vol. 121, pp. 222601, 2022.
Abstract | Links | BibTeX | Tags: Andreev reflection, Mesoscopic quantum transport, phase coherence, Proximity effect, Superconductivity
@article{nokey,
title = {Probing the topological band structure of diffusive multiterminal Josephson junction devices with conductance measurements},
author = {Venkat Chandrasekhar},
url = {https://arxiv.org/abs/2209.04743
https://aip.scitation.org/doi/full/10.1063/5.0125708},
year = {2022},
date = {2022-09-10},
urldate = {2022-09-10},
journal = {Applied Physics Letters},
volume = {121},
pages = {222601},
abstract = {The energy of an Andreev bound state in a clean normal metal in contact with two superconductors disperses with the difference Δϕ in the superconducting phase between the superconductors in much the same way as the energies of electrons in a one-dimensional crystal disperse with the crystal momentum k of the electrons. A normal metal with n superconductors maps on to a n−1 dimensional crystal, each dimension corresponding to the phase difference ϕi between a specific pair of superconductors. The resulting band structure as a function of the phase differences {Δϕi} has been proposed to have a topological nature, with gapped regions characterized by different Chern numbers separated by regions where the gap in the quasiparticle spectrum closes. A similar complex evolution of the quasiparticle spectrum with {Δϕi} has also been predicted for diffusive normal metals in contact with multiple superconductors. Here we show that the variation of the density of states at the Fermi energy of such a system can be directly probed by relatively simple conductance measurements, allowing rapid characterization of the energy spectrum.},
keywords = {Andreev reflection, Mesoscopic quantum transport, phase coherence, Proximity effect, Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The energy of an Andreev bound state in a clean normal metal in contact with two superconductors disperses with the difference Δϕ in the superconducting phase between the superconductors in much the same way as the energies of electrons in a one-dimensional crystal disperse with the crystal momentum k of the electrons. A normal metal with n superconductors maps on to a n−1 dimensional crystal, each dimension corresponding to the phase difference ϕi between a specific pair of superconductors. The resulting band structure as a function of the phase differences {Δϕi} has been proposed to have a topological nature, with gapped regions characterized by different Chern numbers separated by regions where the gap in the quasiparticle spectrum closes. A similar complex evolution of the quasiparticle spectrum with {Δϕi} has also been predicted for diffusive normal metals in contact with multiple superconductors. Here we show that the variation of the density of states at the Fermi energy of such a system can be directly probed by relatively simple conductance measurements, allowing rapid characterization of the energy spectrum.
V. V. Bal; Z. Huang; K. Han; Ariando; T. Venkatesan; V. Chandrasekhar
Low temperature magnetoresistance of (111) (La0.3Sr0.7)(Al0.65Ta0.35)/SrTiO3 Journal Article
In: Physical Review B, vol. 99, pp. 035408, 2019.
Abstract | Links | BibTeX | Tags: epitaxial, magnetic impurity, Magnetism, perovskite, phase coherence, spin glass, Superconductivity
@article{Bal2018,
title = {Low temperature magnetoresistance of (111) (La0.3Sr0.7)(Al0.65Ta0.35)/SrTiO3},
author = {V. V. Bal and Z. Huang and K. Han and Ariando and T. Venkatesan and V. Chandrasekhar},
url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.99.035408},
doi = {https://doi.org/10.1103/PhysRevB.99.035408},
year = {2019},
date = {2019-01-03},
journal = {Physical Review B},
volume = {99},
pages = {035408},
abstract = {The two-dimensional conducting interfaces in SrTiO3-based systems are known to show a variety of coexisting and competing phenomena in a complex phase space. Magnetoresistance measurements, which are typically used to extract information about the various interactions in these systems, must be interpreted with care, since multiple interactions can contribute to the resistivity in a given range of magnetic field and temperature. Here we review all the phenomena that can contribute to transport in SrTiO3-based conducting interfaces at low temperatures. We apply this understanding to the perpendicular magnetoresistance data of the high-mobility system of (111) oriented (La0.3Sr0.7)(Al0.65Ta0.35)O3/STO heterostructures, and find an excess negative magnetoresistance contribution which cannot be explained by weak localization alone. We argue that contributions from magnetic scattering as well as electron-electron interactions, combined with weak localization/antilocalization, can provide a possible explanation for the observed magnetoresistance.},
keywords = {epitaxial, magnetic impurity, Magnetism, perovskite, phase coherence, spin glass, Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The two-dimensional conducting interfaces in SrTiO3-based systems are known to show a variety of coexisting and competing phenomena in a complex phase space. Magnetoresistance measurements, which are typically used to extract information about the various interactions in these systems, must be interpreted with care, since multiple interactions can contribute to the resistivity in a given range of magnetic field and temperature. Here we review all the phenomena that can contribute to transport in SrTiO3-based conducting interfaces at low temperatures. We apply this understanding to the perpendicular magnetoresistance data of the high-mobility system of (111) oriented (La0.3Sr0.7)(Al0.65Ta0.35)O3/STO heterostructures, and find an excess negative magnetoresistance contribution which cannot be explained by weak localization alone. We argue that contributions from magnetic scattering as well as electron-electron interactions, combined with weak localization/antilocalization, can provide a possible explanation for the observed magnetoresistance.
Paul Cadden-Zimansky
Nonlocal Coherence in Normal Metal-Superconductor Nanostructures PhD Thesis
2008.
Links | BibTeX | Tags: Andreev reflection, charge imbalance, crossed andreev reflection, Mesoscopic quantum transport, nanomagnets, phase coherence, Proximity effect, Superconductivity
@phdthesis{Cadden-Zimansky2008,
title = {Nonlocal Coherence in Normal Metal-Superconductor Nanostructures},
author = {Paul Cadden-Zimansky},
url = {http://www.nano.northwestern.edu/wp-content/uploads/2017/09/C-Z-Thesis-Final.pdf},
year = {2008},
date = {2008-12-01},
keywords = {Andreev reflection, charge imbalance, crossed andreev reflection, Mesoscopic quantum transport, nanomagnets, phase coherence, Proximity effect, Superconductivity},
pubstate = {published},
tppubtype = {phdthesis}
}
Zhengfan Zhang; Venkat Chandrasekhar
Signatures of phase coherence in the low-temperature transport properties of multiwall carbon nanotubes Journal Article
In: Physical Review B, vol. 73, no. 7, 2006, ISSN: 1098-0121, 1550-235X.
Links | BibTeX | Tags: Mesoscopic quantum transport, Nanotube, phase coherence
@article{zhang_signatures_2006,
title = {Signatures of phase coherence in the low-temperature transport properties of multiwall carbon nanotubes},
author = { Zhengfan Zhang and Venkat Chandrasekhar},
url = {http://link.aps.org/doi/10.1103/PhysRevB.73.075421},
doi = {10.1103/PhysRevB.73.075421},
issn = {1098-0121, 1550-235X},
year = {2006},
date = {2006-02-01},
urldate = {2016-12-29},
journal = {Physical Review B},
volume = {73},
number = {7},
keywords = {Mesoscopic quantum transport, Nanotube, phase coherence},
pubstate = {published},
tppubtype = {article}
}
Zhigang Jiang; Venkat Chandrasekhar
Quantitative measurements of the thermal resistance of Andreev interferometers Journal Article
In: Physical Review B, vol. 72, pp. 020502(R), 2005.
Abstract | Links | BibTeX | Tags: Andreev reflection, Mesoscopic quantum transport, phase coherence, Proximity effect, Superconductivity
@article{Jiang2005b,
title = {Quantitative measurements of the thermal resistance of Andreev interferometers},
author = {Zhigang Jiang and Venkat Chandrasekhar},
url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.72.020502},
doi = {https://doi.org/10.1103/PhysRevB.72.020502},
year = {2005},
date = {2005-07-08},
journal = {Physical Review B},
volume = {72},
pages = {020502(R)},
abstract = {Using a local thermometry technique, we have been able to quantitatively measure the thermal resistance RT of diffusive Andreev interferometers. We find that RT is strongly enhanced from its normal-state value at low temperatures, and behaves nonlinearly as a function of the thermal current through the sample. We also find that RT oscillates as a function of magnetic flux with a fundamental period corresponding to one flux quantum Φ0=h∕2e, demonstrating the phase-coherent nature of thermal transport in these devices. The magnitude of RT is larger than predicted by recent numerical simulations.},
keywords = {Andreev reflection, Mesoscopic quantum transport, phase coherence, Proximity effect, Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Using a local thermometry technique, we have been able to quantitatively measure the thermal resistance RT of diffusive Andreev interferometers. We find that RT is strongly enhanced from its normal-state value at low temperatures, and behaves nonlinearly as a function of the thermal current through the sample. We also find that RT oscillates as a function of magnetic flux with a fundamental period corresponding to one flux quantum Φ0=h∕2e, demonstrating the phase-coherent nature of thermal transport in these devices. The magnitude of RT is larger than predicted by recent numerical simulations.
Zhigang Jiang
Thermal Transport Near the Normal-Metal/Superconductor Interface in Mesoscopic Devices PhD Thesis
2005.
Links | BibTeX | Tags: Andreev reflection, charge imbalance, Mesoscopic quantum transport, phase coherence, Proximity effect, Superconductivity
@phdthesis{Jiang2005,
title = {Thermal Transport Near the Normal-Metal/Superconductor Interface in Mesoscopic Devices},
author = {Zhigang Jiang},
url = {http://www.nano.northwestern.edu/wp-content/uploads/2017/09/JiangThesis.pdf},
year = {2005},
date = {2005-06-01},
keywords = {Andreev reflection, charge imbalance, Mesoscopic quantum transport, phase coherence, Proximity effect, Superconductivity},
pubstate = {published},
tppubtype = {phdthesis}
}
Z. Jiang; V. Chandrasekhar
Thermal Conductance of Andreev Interferometers Journal Article
In: Physical Review Letters, vol. 94, no. 14, 2005, ISSN: 0031-9007, 1079-7114.
Links | BibTeX | Tags: Andreev reflection, phase coherence, Proximity effect, Superconductivity, thermal transport
@article{jiang_thermal_2005,
title = {Thermal Conductance of Andreev Interferometers},
author = { Z. Jiang and V. Chandrasekhar},
url = {http://link.aps.org/doi/10.1103/PhysRevLett.94.147002},
doi = {10.1103/PhysRevLett.94.147002},
issn = {0031-9007, 1079-7114},
year = {2005},
date = {2005-04-01},
urldate = {2016-12-29},
journal = {Physical Review Letters},
volume = {94},
number = {14},
keywords = {Andreev reflection, phase coherence, Proximity effect, Superconductivity, thermal transport},
pubstate = {published},
tppubtype = {article}
}
Zhi-Gang Jiang; Venkat Chandrasekhar
The symmetry of phase-coherent thermopower oscillations in Andreev interferometers Journal Article
In: Chinese Journal of Physics, vol. 43, no. 3S, pp. 693–701, 2005.
Links | BibTeX | Tags: Andreev reflection, phase coherence, Proximity effect, Superconductivity, thermal transport
@article{jiang_symmetry_2005,
title = {The symmetry of phase-coherent thermopower oscillations in Andreev interferometers},
author = { Zhi-Gang Jiang and Venkat Chandrasekhar},
url = {http://www.airitilibrary.com/Publication/alDetailedMesh?docid=05779073-200506-201210080013-201210080013-693-701},
year = {2005},
date = {2005-01-01},
urldate = {2016-12-28},
journal = {Chinese Journal of Physics},
volume = {43},
number = {3S},
pages = {693--701},
keywords = {Andreev reflection, phase coherence, Proximity effect, Superconductivity, thermal transport},
pubstate = {published},
tppubtype = {article}
}
Z Zhang; D. A Dikin; R. S Ruoff; V Chandrasekhar
Conduction in carbon nanotubes through metastable resonant states Journal Article
In: Europhysics Letters (EPL), vol. 68, no. 5, pp. 713–719, 2004, ISSN: 0295-5075, 1286-4854.
Links | BibTeX | Tags: Mesoscopic quantum transport, Nanotube, phase coherence
@article{zhang_conduction_2004,
title = {Conduction in carbon nanotubes through metastable resonant states},
author = { Z Zhang and D. A Dikin and R. S Ruoff and V Chandrasekhar},
url = {http://stacks.iop.org/0295-5075/68/i=5/a=713?key=crossref.40daace9248237a3af208d6afdfb1034},
doi = {10.1209/epl/i2004-10266-6},
issn = {0295-5075, 1286-4854},
year = {2004},
date = {2004-01-01},
urldate = {2016-12-28},
journal = {Europhysics Letters (EPL)},
volume = {68},
number = {5},
pages = {713--719},
keywords = {Mesoscopic quantum transport, Nanotube, phase coherence},
pubstate = {published},
tppubtype = {article}
}
D. A. Dikin; S. Jung; V. Chandrasekhar
Quantitative measurements of the thermopower of Andreev interferometers Journal Article
In: EPL, vol. 57, no. 4, pp. 564, 2002, ISSN: 0295-5075.
Links | BibTeX | Tags: Andreev reflection, phase coherence, Proximity effect, thermal transport
@article{dikin_quantitative_2002,
title = {Quantitative measurements of the thermopower of Andreev interferometers},
author = { D. A. Dikin and S. Jung and V. Chandrasekhar},
url = {http://iopscience.iop.org/article/10.1209/epl/i2002-00499-9/meta},
doi = {10.1209/epl/i2002-00499-9},
issn = {0295-5075},
year = {2002},
date = {2002-01-01},
urldate = {2016-12-28},
journal = {EPL},
volume = {57},
number = {4},
pages = {564},
keywords = {Andreev reflection, phase coherence, Proximity effect, thermal transport},
pubstate = {published},
tppubtype = {article}
}
José Aumentado
2000.
Links | BibTeX | Tags: AMR, Andreev reflection, charge imbalance, crossed andreev reflection, Magnetism, Mesoscopic quantum transport, phase coherence, Proximity effect, spin transport
@phdthesis{Aumentado2000,
title = {Nonequilibrium and Quantum Transport Phenomena in Mesoscopic Ferromagnet/Superconductor Heterostructures},
author = {José Aumentado},
url = {http://www.nano.northwestern.edu/wp-content/uploads/2017/09/AumentadoThesis.pdf},
year = {2000},
date = {2000-12-01},
keywords = {AMR, Andreev reflection, charge imbalance, crossed andreev reflection, Magnetism, Mesoscopic quantum transport, phase coherence, Proximity effect, spin transport},
pubstate = {published},
tppubtype = {phdthesis}
}
Chen-Jung Chien
Transport Phenomena Near The Normal-Metal/Superconducting Interface In Mesoscopic Devices PhD Thesis
1998.
Links | BibTeX | Tags: Andreev reflection, charge imbalance, Mesoscopic quantum transport, phase coherence, Proximity effect
@phdthesis{Chien1998,
title = {Transport Phenomena Near The Normal-Metal/Superconducting Interface In Mesoscopic Devices},
author = {Chen-Jung Chien},
url = {http://www.nano.northwestern.edu/wp-content/uploads/2017/09/ChienThesis.pdf},
year = {1998},
date = {1998-12-01},
keywords = {Andreev reflection, charge imbalance, Mesoscopic quantum transport, phase coherence, Proximity effect},
pubstate = {published},
tppubtype = {phdthesis}
}
