Cryogenic amplifier for shot noise measurement at 20 mK

Arakawa, Tomoyuki; Nishihara, Yoko; Norimoto, Shota; Kobayashi, Kensuke

doi:10.1063/1.4826681

Cited by 30 publications

(35 citation statements)

References 21 publications

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“…To measure accurately the shot noise, our sample is connected to a resonant (2.58 MHz) LC circuit thermalized at the mixing chamber of the dilution fridge. The signal across this resonator is amplified with an in-house-built cryogenic low-noise amplifier 22 thermalized on the 1 K pot and again at room temperature. The power spectral density of the noise is obtained by fast Fourier transformation of the time-domain signal acquired by a digitizer (National Instruments PCI-5922).…”

Section: The Kondo Effectmentioning

confidence: 99%

Universality of non-equilibrium fluctuations in strongly correlated quantum liquids

et al. 2015

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Interacting quantum many-body systems constitute a fascinating research field because they form quantum liquids with remarkable properties and universal behaviour The idea is that they behave as an ensemble of non-interacting 'quasi-particles'. However, non-equilibrium properties have still to be established and remain a key issue of many-body physics. Here, we show a precise experimental demonstration of Landau Fermi liquid theory extended to the non-equilibrium regime in a zero-dimensional system. Combining transport and ultra-sensitive current noise measurements, we have unambiguously identified the SU(2) (ref. The Kondo effect19 is a typical example of a quantum manybody effect, where a localized spin is screened by the surrounding conduction electrons at low temperature to form a unique correlated ground state. The Kondo state is described well by the Fermi liquid theory at equilibrium 1,9 , which makes it an ideal testbed to go beyond equilibrium. To unveil the universal behaviour of nonequilibrium Fermi liquid 11 , we have used the current fluctuations or shot noise in a Kondo-correlated nanotube quantum dot 18 . When electrons are transmitted through this system, the scattering induces the shot noise, which sensitively reflects the nature of the quasi-particles 20 , as shown in the upper panel of Fig. 1a. A remarkable prediction of the non-equilibrium Fermi liquid theory is that the residual interaction between quasi-particles creates an additional scattering of two quasi-particles which enhances the noise (see the lower panel of Fig. 1a) 10,12-15 . This two-particle scattering is characterized by an effective charge e * larger than e (electron charge). This value, closely related to the Wilson ratio, is universal for the Fermi liquid in the Kondo regime as it depends only on the symmetry group of the system [13][14][15] . Although some aspects of Kondo-associated noise have been reported 8,16,17 , a rigorous, selfconsistent treatment in a regime where universal results apply is at the core of the present work. Actually, by investigating the same nanotube quantum dot in the spin degenerate SU(2) Kondo regime and in the spin-orbit degenerate SU(4) regime, the noise is proved to contain distinct signatures of these two symmetries, confirming theoretical developments of Fermi liquid theory out of equilibrium.In our experiment, we measured the conductance and current noise through a carbon nanotube quantum dot grown by chemical vapour deposition 21 . Iron catalyst was deposited on an oxidized undoped silicon wafer and exposed to 10 mbar of acetylene for 9 s at 900• C. The nanotube was connected with a Pd(6 nm)/Al(70 nm) bilayer deposited by e-gun evaporation. The distance between the contacts is 400 nm and a side gate electrode is deposited to tune the potential of the quantum dot (see Fig. 1b). A magnetic field of 0.08 T is applied to suppress superconductivity of the contacts. To measure accurately the shot noise, our sample is connected to a resonant (2.58 MHz) LC circuit thermalized at the mixing chambe...

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Section: The Kondo Effectmentioning

confidence: 99%

Universality of non-equilibrium fluctuations in strongly correlated quantum liquids

et al. 2015

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“…In addition to the conductance measurement, we performed current noise measurements as follows 31,34 . The voltage fluctuation at 2.8 MHz defined by the resonant circuit is extracted as an output signal of the homemade cryogenic amplifier 34 .…”

Section: B Current Noise Measurementmentioning

confidence: 99%

Finite shot noise and electron heating at quantized conductance in high-mobility quantum point contacts

et al. 2016

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We report a precise experimental study on the shot noise of a quantum point contact (QPC) fabricated in a GaAs/AlGaAs based high-mobility two-dimensional electron gas (2DEG). xThe combination of unprecedented cleanliness and very high measurement accuracy has enabled us to discuss the Fano factor to characterize the shot noise with a precision of 1 %. We observed that the shot noise at zero magnetic field exhibits a slight enhancement exceeding the single particle theoretical prediction, and that it gradually decreases as a perpendicular magnetic field is applied. We also confirmed that this additional noise completely vanishes in the quantum Hall regime. These phenomena can be explained by the electron heating effect near the QPC, which is suppressed with increasing magnetic field.

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“…We measure differential conductance (G(V ) ≡ dI/dV ) at sourcedrain voltage V using a lock-in technique with an ac excitation of 2 µV. The current noise spectral density S I is measured through a resonant LC circuit (2.58 MHz) connected to a low temperature amplifier [32]. The device is set either in the normal (N) state or in the superconducting (S) state by switching on and off a small in-plane magnetic field of 0.08 T, respectively.…”

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Enhanced Shot Noise of Multiple Andreev Reflections in a Carbon Nanotube Quantum Dot in SU(2) and SU(4) Kondo regimes

et al. 2018

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The sensitivity of shot noise to the interplay between Kondo correlations and superconductivity is investigated in a carbon nanotube quantum dot connected to superconducting electrodes. Depending on the gate voltage, the SU (2) and SU (4) Kondo unitary regimes can be clearly identified. We observe enhancement of the shot noise via the Fano factor in the superconducting state. Its divergence at low bias voltage, which is more pronounced in the SU (4) regime than in the SU (2) one, is larger than what is expected from proliferation of multiple Andreev reflections predicted by the existing theories. Our result suggests that Kondo effect is responsible for this strong enhancement.Introduction.-Kondo effect and superconductivity, two typical many-body effects, emerge in various fields of physics such as in heavy fermion systems [1], mesoscopic systems [2,3], and cold atoms [4,5]. Kondo effect arises due to formation of a spin singlet between a localized state and free conduction electrons with the characteristic energy, k B T K , where k B is the Boltzmann constant and T K is the Kondo temperature. An s-wave superconductor, for its part, is characterized by a macroscopic wave function constituted of Cooper pairs singlet with a binding energy ∆. The interplay between those two many-body states has been shown to bring new intriguing fundamental physics such as quantum transitions [6]. Superconductor-quantum dot-superconductor devices (S-QD-S) [7-12] and QD-SQUID [13-15] tuned in the Kondo regime are ideal platforms to study the interplay between the two effects.At equilibrium, a supercurrent is carried by Andreev bound states (ABS) formed in the QD. The Kondo effect manifests itself by screening the magnetic moment of the ground state and induces a first order quantum transition as observed via the current phase relation [10,[13][14][15] and spectroscopy experiments [12]. When the junction is biased with a voltage V , non-equilibrium transport occurs through multiple Andreev reflections (MAR) [7][8][9], where an injected quasiparticle at energy, eV , transfers effectively a charge me through the junction before escaping when the acquired energy, m × eV , is larger than 2∆ [16,[18][19][20].Shot noise, non-equilibrium current fluctuation, is a powerful tool to elucidate such transport mechanisms [17]. For instance, large effective charges due to the MAR mechanism depicted above have been detected in the noise measurement in S-quantum point contact (QPC)-S [21]. Regarding Kondo effect, experiments have demonstrated that the many-body effect creates a pair backscattering, which induces a large effective charge in the non-linear noise [22][23][24]. Thus, it is appealing to look

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Cryogenic amplifier for shot noise measurement at 20 mK

Cited by 30 publications

References 21 publications

Universality of non-equilibrium fluctuations in strongly correlated quantum liquids

Universality of non-equilibrium fluctuations in strongly correlated quantum liquids

Finite shot noise and electron heating at quantized conductance in high-mobility quantum point contacts

Enhanced Shot Noise of Multiple Andreev Reflections in a Carbon Nanotube Quantum Dot in SU(2) and SU(4) Kondo regimes

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