Patrick Krantz; Alex Tyner; Pallab Goswami; Venkat Chandrasekhar
Colossal Spontaneous Hall Effect and Emergent Magnetism in KTaO3 Two-Dimensional Electron Gases Journal Article
In: 2022.
Abstract | Links | BibTeX | Tags: AMR, magnetic impurity, Magnetism, perovskite, Superconductivity
@article{nokey,
title = {Colossal Spontaneous Hall Effect and Emergent Magnetism in KTaO3 Two-Dimensional Electron Gases},
author = {Patrick Krantz and Alex Tyner and Pallab Goswami and Venkat Chandrasekhar},
url = {https://arxiv.org/abs/2209.10534},
year = {2022},
date = {2022-09-21},
urldate = {2022-09-21},
abstract = {There has been intense recent interest in the two-dimensional electron gases (2DEGs) that form at the surfaces and interfaces of KTaO$_3$ (KTO), with the discovery of superconductivity at temperatures significantly higher than those of similar 2DEGs based on SrTiO$_3$ (STO). Here we demonstrate that KTO 2DEGs fabricated under conditions that suppress the superconductivity show a large spontaneous Hall effect at low temperatures. The transverse response is asymmetric in an applied perpendicular magnetic field and becomes hysteretic at millikelvin temperatures. The hysteresis is due to long range magnetic order arising from local Ta$^{4+}$ moments. However, the most striking features of the data are the asymmetry of the transverse response and the large spontaneous transverse resistance at zero field, which can be a significant fraction of the longitudinal resistance and depends on crystal orientation. Both effects are due to the presence of a dominant contribution to the transverse response that is symmetric in perpendicular field, suggesting that its origin is topological in nature. We argue that this contribution arises from Berry curvature dipoles coupled with nonequilibrium conditions induced by the measuring current.},
keywords = {AMR, magnetic impurity, Magnetism, perovskite, Superconductivity},
pubstate = {published},
tppubtype = {article}
}
There has been intense recent interest in the two-dimensional electron gases (2DEGs) that form at the surfaces and interfaces of KTaO$_3$ (KTO), with the discovery of superconductivity at temperatures significantly higher than those of similar 2DEGs based on SrTiO$_3$ (STO). Here we demonstrate that KTO 2DEGs fabricated under conditions that suppress the superconductivity show a large spontaneous Hall effect at low temperatures. The transverse response is asymmetric in an applied perpendicular magnetic field and becomes hysteretic at millikelvin temperatures. The hysteresis is due to long range magnetic order arising from local Ta$^{4+}$ moments. However, the most striking features of the data are the asymmetry of the transverse response and the large spontaneous transverse resistance at zero field, which can be a significant fraction of the longitudinal resistance and depends on crystal orientation. Both effects are due to the presence of a dominant contribution to the transverse response that is symmetric in perpendicular field, suggesting that its origin is topological in nature. We argue that this contribution arises from Berry curvature dipoles coupled with nonequilibrium conditions induced by the measuring current.
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.
Varada Vilas Bal
Transport Measurements on (111) Oriented (La0.3Sr0.7)(Al0.65Ta0.35)O3/SrTiO3 Heterostructures PhD Thesis
Northwestern University, 2018.
Abstract | Links | BibTeX | Tags: epitaxial, Kondo effect, magnetic impurity, Magnetism, perovskite, spin-orbit scattering, Superconductivity, superconductor
@phdthesis{Bal2018b,
title = {Transport Measurements on (111) Oriented (La0.3Sr0.7)(Al0.65Ta0.35)O3/SrTiO3 Heterostructures},
author = {Varada Vilas Bal},
url = {http://www.nano.northwestern.edu/wp-content/uploads/2018/09/BalVarada_PhD_Thesis.pdf},
year = {2018},
date = {2018-09-01},
address = {Department of Physics},
school = {Northwestern University},
abstract = {At the interface of two dissimilar entities, something novel can emerge. This idea has driven a vast amount of fruitful work on semiconductor interfaces, and given us the digi- tal revolution. In the past decade, remarkable progress has been made in the synthesis and understanding of interfaces between oxides, opening up new avenues to explore fundamen- tal emergent physics at the interface, as well as to provide viable candidates to augment or even surpass the performance of conventional semiconductor electronics. The two- dimensional conducting interface in the (001) LaAlO3/SrTiO3 system is the most studied example of oxide interfaces, showing a wide range of coexisting and competing phenomena such as superconductivity, superconductor-insulator transitions, magnetism, and spin- orbit interactions. The (111) oriented LaAlO3/SrTiO3 system has been recently found to have a few surprises of its own, with intriguing anisotropies in many transport properties along different in-plane crystal directions. This thesis presents the first results on a different SrTiO3 based system: the conducting interface between (La0.3Sr0.7)(Al0.65Ta0.35) and (111) oriented SrTiO3, which has a smaller strain as compared to the LaAlO3/SrTiO3 system. Electrical transport measurements at cryogenic temperatures reveal that no systematic anisotropy is seen in transport properties, unlike in the case of (111) oriented LaAlO3/SrTiO3. High-field magnetotransport shows the presence of high-mobility carri- ers at high electron densities, and exhibits multiband behavior, tunable in situ using an electrical back-gate, similar to the LaAlO3/SrTiO3 system. The data allow us to draw specific conclusions about band ordering in the system, and point to possible differences between the band ordering in (111) (La0.3Sr0.7)(Al0.65Ta0.35)O3/SrTiO3 and (001) as well as (111) oriented LaAlO3/SrTiO3. Low-field magnetotransport reveals that a strong spin- orbit interaction emerges in the regime of low electron density, when the high-mobility carriers are depleted from the system, a trend which is opposite to that observed in (001) oriented LaAlO3/SrTiO3. The most striking feature is that at millikelvin temperatures, in the regime of low electron densities, concomitant with the development of strong spin- orbit interaction, magnetic order emerges.},
keywords = {epitaxial, Kondo effect, magnetic impurity, Magnetism, perovskite, spin-orbit scattering, Superconductivity, superconductor},
pubstate = {published},
tppubtype = {phdthesis}
}
At the interface of two dissimilar entities, something novel can emerge. This idea has driven a vast amount of fruitful work on semiconductor interfaces, and given us the digi- tal revolution. In the past decade, remarkable progress has been made in the synthesis and understanding of interfaces between oxides, opening up new avenues to explore fundamen- tal emergent physics at the interface, as well as to provide viable candidates to augment or even surpass the performance of conventional semiconductor electronics. The two- dimensional conducting interface in the (001) LaAlO3/SrTiO3 system is the most studied example of oxide interfaces, showing a wide range of coexisting and competing phenomena such as superconductivity, superconductor-insulator transitions, magnetism, and spin- orbit interactions. The (111) oriented LaAlO3/SrTiO3 system has been recently found to have a few surprises of its own, with intriguing anisotropies in many transport properties along different in-plane crystal directions. This thesis presents the first results on a different SrTiO3 based system: the conducting interface between (La0.3Sr0.7)(Al0.65Ta0.35) and (111) oriented SrTiO3, which has a smaller strain as compared to the LaAlO3/SrTiO3 system. Electrical transport measurements at cryogenic temperatures reveal that no systematic anisotropy is seen in transport properties, unlike in the case of (111) oriented LaAlO3/SrTiO3. High-field magnetotransport shows the presence of high-mobility carri- ers at high electron densities, and exhibits multiband behavior, tunable in situ using an electrical back-gate, similar to the LaAlO3/SrTiO3 system. The data allow us to draw specific conclusions about band ordering in the system, and point to possible differences between the band ordering in (111) (La0.3Sr0.7)(Al0.65Ta0.35)O3/SrTiO3 and (001) as well as (111) oriented LaAlO3/SrTiO3. Low-field magnetotransport reveals that a strong spin- orbit interaction emerges in the regime of low electron density, when the high-mobility carriers are depleted from the system, a trend which is opposite to that observed in (001) oriented LaAlO3/SrTiO3. The most striking feature is that at millikelvin temperatures, in the regime of low electron densities, concomitant with the development of strong spin- orbit interaction, magnetic order emerges.
Jonghwa Eom
Electrical Properties of Mesoscopic Spin Glasses PhD Thesis
1998.
Links | BibTeX | Tags: magnetic impurity, Magnetism, Mesoscopic quantum transport, spin glass, spin transport
@phdthesis{Eom1998,
title = {Electrical Properties of Mesoscopic Spin Glasses},
author = {Jonghwa Eom},
url = {http://www.nano.northwestern.edu/wp-content/uploads/2017/09/EomThesis.pdf},
year = {1998},
date = {1998-06-01},
keywords = {magnetic impurity, Magnetism, Mesoscopic quantum transport, spin glass, spin transport},
pubstate = {published},
tppubtype = {phdthesis}
}
G. Neuttiens; J. Eom; C. Strunk; Hugo Pattyn; Christian Van Haesendonck; Yvan Bruynseraede; V. Chandrasekhar
Thermoelectric effects in mesoscopic AuFe spin-glass wires Journal Article
In: EPL (Europhysics Letters), vol. 42, no. 2, pp. 185, 1998.
Links | BibTeX | Tags: Kondo effect, magnetic impurity, spin glass, thermal transport
@article{neuttiens_thermoelectric_1998,
title = {Thermoelectric effects in mesoscopic AuFe spin-glass wires},
author = { G. Neuttiens and J. Eom and C. Strunk and Hugo Pattyn and Christian Van Haesendonck and Yvan Bruynseraede and V. Chandrasekhar},
url = {http://iopscience.iop.org/article/10.1209/epl/i1998-00228-6/fulltext/42213.html},
year = {1998},
date = {1998-01-01},
urldate = {2016-12-29},
journal = {EPL (Europhysics Letters)},
volume = {42},
number = {2},
pages = {185},
keywords = {Kondo effect, magnetic impurity, spin glass, thermal transport},
pubstate = {published},
tppubtype = {article}
}
G. Neuttiens; J. Eom; C. Strunk; V. Chandrasekhar; C. Van Haesendonck; Y. Bruynseraede
Absence of size dependence in the spin-glass resistivity of AuFe wires? Journal Article
In: EPL, vol. 34, no. 8, pp. 617, 1996, ISSN: 0295-5075.
Links | BibTeX | Tags: Kondo effect, magnetic impurity, spin glass
@article{neuttiens_absence_1996,
title = {Absence of size dependence in the spin-glass resistivity of AuFe wires?},
author = { G. Neuttiens and J. Eom and C. Strunk and V. Chandrasekhar and C. Van Haesendonck and Y. Bruynseraede},
url = {http://iopscience.iop.org/article/10.1209/epl/i1996-00505-4/meta},
doi = {10.1209/epl/i1996-00505-4},
issn = {0295-5075},
year = {1996},
date = {1996-01-01},
urldate = {2016-12-29},
journal = {EPL},
volume = {34},
number = {8},
pages = {617},
keywords = {Kondo effect, magnetic impurity, spin glass},
pubstate = {published},
tppubtype = {article}
}
J. Eom; G. Neuttiens; C. Strunk; C. Van Haesendonck; Y. Bruynseraede; V. Chandrasekhar
Asymmetric Nonlinear Differential Resistance of Mesoscopic AuFe Spin-Glass Wires Journal Article
In: Physical review letters, vol. 77, no. 11, pp. 2276, 1996.
Links | BibTeX | Tags: Kondo effect, magnetic impurity, spin glass, thermal transport
@article{eom_asymmetric_1996,
title = {Asymmetric Nonlinear Differential Resistance of Mesoscopic AuFe Spin-Glass Wires},
author = { J. Eom and G. Neuttiens and C. Strunk and C. Van Haesendonck and Y. Bruynseraede and V. Chandrasekhar},
url = {http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.77.2276},
year = {1996},
date = {1996-01-01},
urldate = {2016-12-28},
journal = {Physical review letters},
volume = {77},
number = {11},
pages = {2276},
keywords = {Kondo effect, magnetic impurity, spin glass, thermal transport},
pubstate = {published},
tppubtype = {article}
}
V. Chandrasekhar; P. Santhanam; N. A. Penebre; R. A. Webb; H. Vloeberghs; C. Van Haesendonck; Y. Bruynseraede
Absence of size dependence of the Kondo resistivity Journal Article
In: Phys. Rev. Lett., vol. 72, no. 13, pp. 2053, 1994.
Abstract | Links | BibTeX | Tags: Kondo effect, magnetic impurity, Mesoscopic quantum transport
@article{chandrasekhar_absence_1994,
title = {Absence of size dependence of the Kondo resistivity},
author = { V. Chandrasekhar and P. Santhanam and N. A. Penebre and R. A. Webb and H. Vloeberghs and C. Van Haesendonck and Y. Bruynseraede},
url = {http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.72.2053},
doi = {10.1103/PhysRevLett.72.2053},
year = {1994},
date = {1994-01-01},
urldate = {2016-12-28},
journal = {Phys. Rev. Lett.},
volume = {72},
number = {13},
pages = {2053},
abstract = {We have measured the low temperature resistivity of AuFe wires in the dilute magnetic impurity limit as a function of wire width, temperature, and magnetic field. When the width dependence of the electron-electron interaction contribution to the resistivity is taken into account, the temperature dependence of the remaining Kondo contribution to the resistivity of all samples with the same impurity concentration is identical. Similar behavior is observed for the magnetic field dependent resistivity. Thus, the Kondo contribution to the resistivity is independent of width down to 38 nm, much smaller than the Kondo length $textbackslashensuremathtextbackslashxi_textbackslashmathitK$=textbackslashensuremathtextbackslashElzxh$textbackslashmathitv_textbackslashmathitF$/$textbackslashmathitk_textbackslashmathitB$$textbackslashmathitŦ_textbackslashmathitK$textbackslashensuremathtextbackslashapproxeq10 textbackslashensuremathtextbackslashmum.},
keywords = {Kondo effect, magnetic impurity, Mesoscopic quantum transport},
pubstate = {published},
tppubtype = {article}
}
We have measured the low temperature resistivity of AuFe wires in the dilute magnetic impurity limit as a function of wire width, temperature, and magnetic field. When the width dependence of the electron-electron interaction contribution to the resistivity is taken into account, the temperature dependence of the remaining Kondo contribution to the resistivity of all samples with the same impurity concentration is identical. Similar behavior is observed for the magnetic field dependent resistivity. Thus, the Kondo contribution to the resistivity is independent of width down to 38 nm, much smaller than the Kondo length $textbackslashensuremathtextbackslashxi_textbackslashmathitK$=textbackslashensuremathtextbackslashElzxh$textbackslashmathitv_textbackslashmathitF$/$textbackslashmathitk_textbackslashmathitB$$textbackslashmathitŦ_textbackslashmathitK$textbackslashensuremathtextbackslashapproxeq10 textbackslashensuremathtextbackslashmum.
V. Chandrasekhar; P. Santhanam; D. E. Prober
Effect of spin-orbit and spin-flip scattering on conductance fluctuations Journal Article
In: Physical Review B, vol. 42, no. 10, pp. 6823, 1990.
Links | BibTeX | Tags: Conductance fluctuations, magnetic impurity, spin-orbit scattering
@article{chandrasekhar_effect_1990,
title = {Effect of spin-orbit and spin-flip scattering on conductance fluctuations},
author = { V. Chandrasekhar and P. Santhanam and D. E. Prober},
url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.42.6823},
year = {1990},
date = {1990-01-01},
urldate = {2015-10-23},
journal = {Physical Review B},
volume = {42},
number = {10},
pages = {6823},
keywords = {Conductance fluctuations, magnetic impurity, spin-orbit scattering},
pubstate = {published},
tppubtype = {article}
}
