Very low friction rotator for use at low temperatures and high magnetic fields

Palm, E. C.; Murphy, T. P.

doi:10.1063/1.1149571

Cited by 28 publications

(21 citation statements)

References 3 publications

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“…2 the same magnetoresistance data obtained on the sample with p=8.2×10 10 cm −2 are replotted as the dependencies ρ xx (T ) at several field values to clarify the modification of the dρ xx /dT and its sign change at the field of 7.2 T. The samples were mounted on a one axis rotator 16 . That allowed to determine the sample position at which the field was aligned parallel to the quantum well plane with an error of less than 10 minutes.…”

Section: Experiments and Discussionmentioning

confidence: 99%

Large magnetoresistance of a dilutep-Si/SiGe/Siquantum well in a parallel magnetic field

Drichko¹,

Smirnov²,

Суслов³

et al. 2009

Phys. Rev. B

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We report the results of an experimental study of the magnetoresistance ρxx in two samples of p-Si/SiGe/Si with low carrier concentrations p=8.2×10 10 cm −2 and p=2×10 11 cm −2 . The research was performed in the temperature range of 0.3-2 K in the magnetic fields of up to 18 T, parallel to the two-dimensional (2D) channel plane at two orientations of the in-plane magnetic field B against the current I: B ⊥ I and B I. In the sample with the lowest density in the magnetic field range of 0-7.2 T the temperature dependence of ρxx demonstrates the metallic characteristics (dρxx/dT >0). However, at B =7.2 T the derivative dρxx/dT reverses the sign. Moreover, the resistance depends on the current orientation with respect to the in-plane magnetic field. At B ∼ = 13 T there is a transition from the dependence ln(∆ρxx/ρ0) ∝ B 2 to the dependence ln(∆ρxx/ρ0) ∝ B . The observed effects can be explained by the influence of the in-plane magnetic field on the orbital motion of the charge carriers in the quasi-2D system.

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Section: Experiments and Discussionmentioning

confidence: 99%

Large magnetoresistance of a dilutep-Si/SiGe/Siquantum well in a parallel magnetic field

Drichko¹,

Smirnov²,

Суслов³

et al. 2009

Phys. Rev. B

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“…The calorimeter fits into a top-loading single-axis probe [37] capable of 360 degree rotation at base temperature with a resolution of 0.02 degrees. The sample is weakly thermally linked to a temperature controlled platform inside the vacuum calorimeter, which is in turn weakly linked to the cryogenic mixture.…”

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Calorimetric Measurements of Magnetic-Field-Induced Inhomogeneous Superconductivity Above the Paramagnetic Limit

et al. 2017

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We report the first magneto-caloric and calorimetric observations of a magnetic-field-induced phase transition within a superconducting state to the long-sought exotic "FFLO" superconducting state first predicted over 50 years ago. Through the combination of bulk thermodynamic calorimetric and magnetocaloric measurements in the organic superconductor κ -(BEDT-TTF)2Cu(NCS)2, as a function of temperature, magnetic field strength, and magnetic field orientation, we establish for the first time that this field-induced first-order phase transition at the paramagnetic limit Hp for traditional superconductivity is to a higher entropy superconducting phase uniquely characteristic of the FFLO state. We also establish that this high-field superconducting state displays the bulk paramagnetic ordering of spin domains required of the FFLO state. These results rule out the alternate possibility of spin-density wave (SDW) ordering in the high field superconducting phase. The phase diagram determined from our measurements -including the observation of a phase transition into the FFLO phase at Hp -is in good agreement with recent NMR results and our own earlier tunnel-diode magnetic penetration depth experiments, but is in disagreement with the only previous calorimetric report. 74.25.Dw, 74.70.Kn, 74.25.Ha Magnetic fields destroy superconductivity. In most cases, this occurs due to the formation of magnetic vortices -non-superconducting regions containing a magnetic field flux line shielded by circulating electrons -which increase in density as the magnetic field strength increases, ultimately displacing the superconducting phase. In the absence of magnetic vortices, the paramagnetic spin susceptibility of the electrons making up the superconducting "Cooper pairs" places another upper limit on superconductivity in magnetic fields. Because the electrons in these pairs have oppositely aligned magnetic moments (spins), the reduction in magnetic energy due to flipping the spin of an individual electron will exceed the reduction in electronic energy available from the formation of the Cooper pairs above a critical magnetic field H P known as the Clogston-Chandrasakar paramagnetic limit [1,2]. A phase transition from the superconducting to the normal metallic state is therefore expected at H P . Some 50 years ago, however, Fulde and Ferrell [3] and Larkin and Ovchinnikov [4] predicted that there might instead be a phase transition at H P to a different superconducting phase in which paramagnetic spin domains coexist with a spatially inhomogeneous superconducting phase. This "FFLO state" is expected to exist at fields above H P in electronically clean, anisotropic superconducting materials [5][6][7].The search for inhomogeneous superconductivity has spanned many years, and began in low dimensional single layers of superconducting materials [8]. The first clear calorimetric observations of a bulk field induced phase transition between two superconducting phases were observed in the heavy fermion compound CeCoIn 5 [9,10]. This tran...

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“…Their values coincide with the results of our numerical self-consistent LSDA calculation. All angular-dependent measurements were carried out at T = 40 mK in a top-loading dilution refrigerator equipped with an in-situ rotator [29] placed inside a 33T resistive magnet. A low-frequency (∼ 7 Hz) lock-in technique at a current I = 10 nA is used.…”

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Reorientation of Anisotropy in a Square Well Quantum Hall Sample

et al. 2000

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We have measured magnetotransport at half-filled high Landau levels in a quantum well with two occupied electric subbands. We find resistivities that are isotropic in perpendicular magnetic field but become strongly anisotropic at ν = 9/2 and 11/2 on tilting the field. The anisotropy appears at an in-plane field, Bip ∼ 2.5 T, with the easy-current direction parallel to Bip but rotates by 90 • at Bip ∼ 10 T and points now in the same direction as in single-subband samples. This complex behavior is in quantitative agreement with theoretical calculations based on a unidirectional charge density wave state model.A two-dimensional (2D) electron gas is an attractive system for many-body physics studies [1,2]. A particularly rich variety of phenomena associated with strong interactions among electrons appears in the regime of the fractional quantum Hall effect (FQHE) [3,4]. During much of the last decade, studies of the FQHE have focused on even-denominator Landau level filling factors [5,6] such as the compressible ν = 1/2 state and the ν = 5/2 incompressible quantum Hall fluid. Most recently, strongly anisotropic transport has been observed in high quality GaAs/Al x Ga 1−x As single heterojunctions [7][8][9][10][11] at filling factors ν = 9/2, 11/2, etc., and in 2D hole systems [12] starting at ν = 5/2. In these experiments, the magnetoresistance shows a strong peak in one current direction and a deep minimum in the perpendicular current direction. Tilting the magnetic field away from the sample normal causes the high resistance direction to change from its original orientation to the in-plane magnetic field direction.The origin of the magnetotransport anisotropy has not been firmly established yet. The most appealing interpretation suggests that the 2D electron gas spontaneously breaks the translational symmetry by forming a unidirectional charge density wave (UCDW), as predicted by Hartree-Fock theory [13,14]. This idea has spurred much theoretical interest [15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Because of uncertainty about the reliability of this Hartree-Fock prediction, there has been a special emphasis [19,20] placed on tests of its ability to explain experimental results on "stripe" orientation in tilted magnetic fields. In particular, Jungwirth et al. [19] carried out detailed many-body RPA/HartreeFock calculations combined with a self-consistent localspin-density-approximation (LSDA) description of oneparticle states in experimental sample geometries. For the sample parameters of the traditional, single-interface specimens of Refs. [10,11] with a single electric subband occupied, the theory [19,20] gives stripes oriented perpendicular to the field, consistent with experiment.A theoretical study [19] of UCDWs in parabolic quantum wells that have two subbands occupied in zero magnetic field, has predicted much more complex behavior of the UCDW state, including stripe states induced by an in-plane field and rotation of stripe orientation at critical in-plane field strengths. A comparison betwe...

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Very low friction rotator for use at low temperatures and high magnetic fields

Abstract: Low-noise rotating sample holder for ultrafast transient spectroscopy at cryogenic temperatures Rev. Sci. Instrum. 78, 053102 (2007);

Cited by 28 publications

References 3 publications

Large magnetoresistance of a dilutep-Si/SiGe/Siquantum well in a parallel magnetic field

Large magnetoresistance of a dilutep-Si/SiGe/Siquantum well in a parallel magnetic field

Calorimetric Measurements of Magnetic-Field-Induced Inhomogeneous Superconductivity Above the Paramagnetic Limit

Reorientation of Anisotropy in a Square Well Quantum Hall Sample

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