Electron–phonon heat exchange in layered nano-systems

Anghel, Dragos-Victor; Cojocaru, S.

doi:10.1016/j.ssc.2015.11.019

Cited by 5 publications

(32 citation statements)

References 31 publications

(82 reference statements)

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“…At working temperatures, which are below 100 mK, the electron system in the normal metal is very weakly coupled to the phonons system. [25][26][27][28] This allows for the independent thermalization of the electrons system, at temperature T e , and of the phonons system, at temperature T ph . Then, the heat power between the electrons system and phonons system may be written in general aṡ…”

Section: Response Of the Cold Electron Bolometermentioning

confidence: 99%

“…We use the experimental values x = 5 and Σ ep = 4 × 10 9 Wm −3 K −513 instead of theoretical ones, calculated more recently, because the values existing in the literature (both, theoretical and experimental) vary significantly from model to model and from sample to sample (see the diversity of results presented, for example, in Refs. [13,[25][26][27][37][38][39][40][41][42][43]). For this reason we give priority to the measured parameters, in order to make more realistic calculations.…”

Section: Response Of the Cold Electron Bolometermentioning

confidence: 99%

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Cold-Electron Bolometer as a 1-cm-Wavelength Photon Counter

Anghel

Kuzmin

2020

Phys. Rev. Applied

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We investigate theoretically the possibility of using the cold-electron bolometer (CEB) as a counter for 1 cm wavelength (30 GHz) photons. To reduce the flux of photons from the environment, which interact with the detector, the bath temperature is assumed to be below 50 mK. At such temperatures, the time interval between two subsequent photons of 30 GHz that hit the detector is more than 100 hours, on average, for a frequency window of 1 MHz. Such temperatures allow the observation of the physically significant photons produced in rare events, like the axions conversion (or Primakoff conversion) in magnetic field. We present the general formalism for the detector's response and noise, together with numerical calculations for proper experimental setups. We observe that the current-biased regime is favorable, due to lower noise, and allows for the photons counting at least below 50 mK. For the experimental setups investigated here, the voltage-biased CEBs may also work as photons counters, but with less accuracy and eventually at bath temperatures below 40 mK. The voltage-biased setups also require smaller volumes of the normal metal island of the detector.

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Section: Response Of the Cold Electron Bolometermentioning

confidence: 99%

Section: Response Of the Cold Electron Bolometermentioning

confidence: 99%

Cold-Electron Bolometer as a 1-cm-Wavelength Photon Counter

Anghel

Kuzmin

2020

Phys. Rev. Applied

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“…The same is true for P (1) QWa /P (1) QW s . The sharp crests that appear parallel to the T e axis are exceptions to the simple power-law dependence of P 2D QW and are not discussed here (see [11] for details).…”

Section: Dmentioning

confidence: 99%

“…This interaction is described by the deformation potential Hamiltonian [10][11][12] where E F is the Fermi energy of the electrons, A is the area of the metallic film, d is the thickness (see Fig. 1), Ψ † (r) and Ψ(r) are the electron field creation and annihilation operators, respectively, whereas u is the phonon field.…”

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confidence: 99%

Heat Exchange Between Electrons and Phonons in Nanosystems at Sub-Kelvin Temperatures

Anghel

Cojocaru

2018

EPJ Web Conf.

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Abstract. Ultra-sensitive nanoscopic detectors for electromagnetic radiation consist of thin metallic films deposited on dielectric membranes. The metallic films, of thickness d of the order of 10 nm, form the thermal sensing element (TSE), which absorbs the incident radiation and measures its power flux or the energies of individual photons. To achieve the sensitivity required for astronomical observations, the TSE works at temperatures of the order of 0.1 K. The dielectric membranes are used as support and for thermal insulation of the TSE and are of thickness L − d of the order of 100 nm (L being the total thickness of the system). In such conditions, the phonon gas in the detector assumes a quasi-two-dimensional distribution, whereas quantization of the electrons wavenumbers in the direction perpendicular to the film surfaces leads to the formation of quasi twodimensional electronic sub-bands. The heat exchange between electrons and phonons has an important contribution to the performance of the device and is dominated by the interaction between the electrons and the antisymmetric acoustic phonons.High sensitivity electromagnetic radiation detectors for space applications are nanometer-size devices which work at sub-Kelvin temperatures [1,2]. Such a detector consists of a thermal sensing element (TSE) which is deposited on a supporting membrane. The TSE is formed of one or several metallic layers and has the role of absorbing and measuring the incident electromagnetic radiation. The supporting membrane is dielectric and provides the thermal insulation of the TSE from the bulk material [1][2][3][4]. To ensure the level of sensitivity required by the astrophysical observations, the thickness of the TSE should be of the order of 10 nm, the thickness of the supporting membrane is of the order of 100 nm, whereas the working temperature of the device may be about 100 mK [5,6]. The layers of materials that form the detector are shown schematically in Fig. 1.The TSE may consist of a normal metal strip coupled to a superconducting antenna [2,3,[5][6][7][8][9]. When the incident radiation is absorbed, its energy is dissipated into the normal metal strip. At the detector's working temperature, the electrons are weakly coupled to the lattice and therefore we can associate an effective temperature to each of these subsystems: T e will denote the temperature of the electrons and T ph will denote the temperature of the lattice (phonons).Being at different temperatures, a net heat power P flows between the electron system and the phonon system, due to the electron-phonon interaction. This interaction is described by the deformation potential Hamiltonian [10-12]

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“…(1b), it was observed that s may take also fractional values: if the phonon gas is 2D and the electron gas distribution is a superposition of 2D conduction bands, then x = 3.5. 3,4 The exponent x depends on the effective dimensionality of the phonon gas, but the latter may change with temperature, as we discussed above. [5][6][7][8] Therefore, in a temperature range where the dimensionality of the phonon gas changes, the exponent x may also change,…”

Section: Introductionmentioning

confidence: 99%

Crossover temperature in electron–phonon heat exchange in layered nanostructures

2019

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We study theoretically the effect of the effective dimensionality of the phonon gas distribution on the heat exchange between electrons and phonons in layered nanostructures. If we denote the electrons temperature by Te and the phonons temperature by T ph , then the total heat power P is proportional-in general-to T x e −T x ph , the exponent x being dependent on the effective dimensionality of the phonon gas distribution. If we vary the temperature in a wide enough range, the effective dimensionality of the phonon gas distribution changes going through a crossover around some temperature, TC . These changes are reflected by a change in x. On one hand, in a temperature range well below a crossover temperature TC only the lowest branches of the phonon modes are excited.They form a (quasi) two-dimensional gas, with x = 3.5. On the other hand, well above TC , the phonon gas distribution is quasi three-dimensional and one would expect to recover the three dimensional results, with x = 5. But this is not the case in our layered structure. The exponent x has a complicated, non-monotonous dependence on temperature forming a "plateau region" just after the crossover temperature range, with x between 4.5 and 5. After the plateau region, x decreases, reaching values between 3.5 and 4 at the highest temperature used in our numerical calculations, which is more than 40 times higher than TC .

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Electron–phonon heat exchange in layered nano-systems

Cited by 5 publications

References 31 publications

Cold-Electron Bolometer as a 1-cm-Wavelength Photon Counter

Cold-Electron Bolometer as a 1-cm-Wavelength Photon Counter

Heat Exchange Between Electrons and Phonons in Nanosystems at Sub-Kelvin Temperatures

Crossover temperature in electron–phonon heat exchange in layered nanostructures

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