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Observation of Berry curvature fluctuations from incipient polar order in an oxide interface
Authors:
S. Avraham,
D. Gitman,
P. Matus,
S. Sandik,
E. Raz,
S. Jana,
M. Dahan,
T. Holder,
Y. Dagan
Abstract:
Diagnosing hidden local orders at buried interfaces remains a central challenge in the design and characterization of quantum materials. Second-order electrical responses, such as the nonlinear Hall effect, probe inversion-symmetry-breaking terms invisible to linear transport, offering a direct window into these nanoscale environments via the quantum geometry of Bloch electrons. Here, we utilize…
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Diagnosing hidden local orders at buried interfaces remains a central challenge in the design and characterization of quantum materials. Second-order electrical responses, such as the nonlinear Hall effect, probe inversion-symmetry-breaking terms invisible to linear transport, offering a direct window into these nanoscale environments via the quantum geometry of Bloch electrons. Here, we utilize $\text{KTaO}_3$, a complex oxide driven by strong tantalum $5d$ spin-orbit coupling and interfacial inversion symmetry breaking, to demonstrate that second-harmonic resistivities exhibit large, reproducible mesoscopic fluctuations. Remarkably, these fluctuations persist in macroscopically large ($200\,μ\text{m}$) devices and are ubiquitous across all studied surface orientations, even where macroscopic conductivity strictly adheres to underlying crystal symmetries. We propose that these robust, magnetic-field-driven interference patterns arise from local structural symmetry breaking, driven by incipient ferroelectric polarization pinned to the interfacial impurity landscape. This defect-pinned polar mechanism is firmly supported by the signal's suppression above $10\text{ K}$ due to phase decoherence, and a complete loss of mesoscopic memory upon thermal cycling above $40\text{ K}$. By linking quantum geometry to dynamic lattice ordering, our findings establish nonlinear mesoscopic transport as a powerful new characterization tool, capable of revealing local polar tendencies and hidden structural orders in complex materials that remain fundamentally invisible to conventional probes.
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Submitted 18 June, 2026;
originally announced June 2026.
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Measurement of the radiative and non-radiative decay rates of single CdSe nanocrystals through controlled modification of their spontaneous emission
Authors:
X. Brokmann,
L. Coolen,
Maxime Dahan,
J. P. Hermier
Abstract:
We present a simple method to measure the radiative and non-radiative recombination rates of individual fluorescent emitters at room temperature. By placing a single molecule successively close and far from a dielectric interface and simultaneously measuring its photoluminescence decay and its orientation, both the radiative and non-radiative recombination rates can be determined. For CdSe nanoc…
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We present a simple method to measure the radiative and non-radiative recombination rates of individual fluorescent emitters at room temperature. By placing a single molecule successively close and far from a dielectric interface and simultaneously measuring its photoluminescence decay and its orientation, both the radiative and non-radiative recombination rates can be determined. For CdSe nanocrystals, our results demonstrate that the fluorescence quantum efficiency, determined at the single molecule level, is 98% in average, far above the value expected from conventional ensemble experiments. The bi-dimensionnal nature of the transition dipole is also directly evidenced from a single particle measurement.
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Submitted 4 August, 2004;
originally announced August 2004.
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Statistical Aging and Non Ergodicity in the Fluorescence of Single Nanocrystals
Authors:
X. Brokmann,
J. -P. Hermier,
G. Messin,
P. Desbiolles,
J. -P. Bouchaud,
M. Dahan
Abstract:
The relation between single particle and ensemble measurements is adressed for semiconductor CdSe nanocrystals. We record their fluorescence at the single molecule level and analyse their emission intermittency, which is governed by unusual random processes known as Levy statistics. We report the observation of statistical aging and ergodicity breaking, both related to the occurrence of Levy sta…
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The relation between single particle and ensemble measurements is adressed for semiconductor CdSe nanocrystals. We record their fluorescence at the single molecule level and analyse their emission intermittency, which is governed by unusual random processes known as Levy statistics. We report the observation of statistical aging and ergodicity breaking, both related to the occurrence of Levy statistics. Our results show that the behaviour of ensemble quantities, such as the total fluorescence of an ensemble of nanocrystals, can differ from the time averaged individual quantities, and must be interpreted with care.
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Submitted 11 November, 2002; v1 submitted 8 November, 2002;
originally announced November 2002.