E. Balthes's research while affiliated with French National Centre for Scientific Research and other places
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Publications (55)
Investigations of the structures and electronic properties of neat single crystals of the organic metals Theta-(BEDT-TTF)2I3 and ThetaT-(BEDT-TTF)2I3 ---a tempered phase of Theta-(BEDT-TTF)2I3 ---are presented and compared. It will be shown that in contrast to the Theta -phase crystals, where only 30% of the crystals become superconducting at 3.6K...
The Fermi surface (FS) of the new organic metal (BEDT-TTF)4[ Ni(dto)2] has been investigated by de Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) experiments. In both quantum oscillations with two different frequencies Fα = 634 T and Fβ = 4245 T are observed. These results confirm the calculated FS, which consists of one-dimensional and two-dim...
In the strongly two-dimensional (2D) organic metal
κ-(BEDT − TTF)2I3 anomalous damping effects of the
magneto-quantum oscillations are reported for the special
conditions Θ = 0° (i.e., B⊥ to the conducting
planes), B > 12 T and T < 1 K. A new observed
oscillation frequency F0 = 13.2 T is found to control
these effects at low Landau level filling fa...
This work presents quantum oscillation experiments in quasi-twodimensional multilayer organic metals. They show that low integer Landau level filling factors nare present in the two-dimensional organic metal k-(BEDT-TTF)2I3 and give strong indications for the existence of the fractional filling factor n=½ in this material. By this the work shows th...
SdH - measurements were performed on the organic metal (TMTSF)2ReO4 under a pressure of 8.5 kbar. Fast oscillations (FO) with a frequency of 330T could be reproduced already above 4.5T for
temperatures below 4.5K. It could be shown, that these oscillations are not influenced by field induced spin-density-waves
(FISDW’s) with a frequency of 28T. The...
SdH — measurements were performed on the organic metal (TMTSF)2ReO4 under a pressure of 8.5 kbar. Fast oscillations (FO) with a frequency of 330T could be reproduced already above 4.5T for
temperatures below 4.5K. It could be shown, that these oscillations are not influenced by field induced spin-density-waves
(FISDW’s) with a frequency of 28T. The...
Quantum oscillation experiments were performed on Θ-(BEDT-TTF)2I3 crystals. In the neat crystals used here, quantum oscillations for the α-orbit (Fα=780T) are already observed at a field of 2T and the magnetic breakdown for the β-orbit (Fβ=4200T) occurs at 3T. The warping of the Fermi-surface of the α-orbit and the β-orbit could be determined to be...
In the two-dimensional (2D) organic metal κ-(BEDT-TTF)2I3 the low integer Landau level filling factors ν=1–4 are observed under specific experimental conditions. In high magnetic fields even the presence of the fractional ν=1/2 is strongly indicated in this multilayer material. These ν are detected by the chemical potential μ, i.e. a thermodynamic...
The charge-transfer salt [ (BEDT-TTF)$_{4}$] $^{2+}$[ Ni(dto)$_{2}$] $^{2-}$ is a quasi two-dimensional organic metal [1]. This is confirmed by the resistivity ratio $\rho _{c}$/$\rho _{(a,b)}=100$ at 300K, where (a,b) represents the high conducting plane. The material shows strong quantum oscillations (QOs) above about 1.2T (at 20mK) with two QO f...
Measurements of magneto-transport on the organic superconductor kappa
-(BEDT-TTF){2}I{3} in magnetic fields up to 23 T at 0.48 K under
hydrostatic pressures up to 9 kbar are reported. In this pronounced
two-dimensional (2D) electronic system strong anomalous damping effects
of Shubnikov-de Haas (SdH) oscillations are observed under very specific
ex...
Quantum oscillation experiments were performed on high quality single crystals of Θ-(BEDT-TTF)2I3. Their electronic properties are similar to those of crystals of Θ-(BEDT-TTF) 2(I3)1-x(AuI2)x (x < 0.02). Nevertheless, in the neat crystals used here, quantum oscillations for the α-orbit (Fα= 780 T) are observed already at a field of 2 T, and the mag...
The detection of the fractional Landau level filling factor ν = 1/2 and low integer filling factors in the two-dimensional multilayer organic metal κ-(BEDT-TTF)2I3 is presented, which shows the occur- rence of electron localisation and electron-electron correlation in this bulk metallic two-dimensional system. These effects are found in the normal...
Quantum oscillation (QO) experiments on two organic metals, the highly two-dimensional (2D) electronic systems, were discussed. Comparitive Qo measurements on the Q2D system (BEDT-TTF)4[Ni(dto)2] and the 2D system κ-(BEDT-TTF)2I3 showed that for given strong two-dimensionality the field orientation plays a special role. It was found that the influe...
In the strongly two-dimensional (2D) organic metal K-(BEDT- TTF)(2)I-3, sawtooth oscillations of the chemical potential mu are observed by means of Shubnikov-de Haas and de Haas-van Alphen experiments. The sawtooth shape of these oscillations of mu corresponds to the behaviour of a 2D canonical ensemble of electrons. In contrast to preceding invest...
In the two-dimensional (21)) multilayer organic metal kappa- (BEDT-TTF)(2)I-3 strong electron correlations are present at magnetic fields B > 12 T and temperatures T < 1 K. These correlations manifest themselves in strong anomalous damping effects of magnetoquantum oscillations at high magnetic fields, which are controlled by the low Landau level f...
The magnetic-field, temperature, and angular dependence of the interlayer magnetoresistance of two different quasi-two-dimensional (2D) organic superconductors is reported. For $\kappa$-(BEDT-TTF)$_2$I$_3$ we find a well-resolved peak in the angle-dependent magnetoresistance at $\Theta = 90^\circ$ (field parallel to the layers). This clear-cut proo...
The effect of pressure on the B-T phase diagram of α-(BEDT-TTF)2KHg(SCN)4 is studied. The measured phase lines can be well described by a recent model of a charge-density wave system with varying nesting conditions. A remarkable increase of the transition temperature with magnetic field is found in a certain pressure and field range. We associate t...
The magnetic anisotropy of the cyclic octanuclear Fe(III) cluster [Cs subsetFe(8)[N(CH(2)CH(2)O)(3)](8)]Cl was investigated. Based on a spin Hamiltonian formalism and the consequent use of all symmetries, the magnetic anisotropy could be calculated exactly to first order, i.e., in the strong exchange limit. Experimentally, the magnetic anisotropy w...
ne Haas-van Alphen and Shubnikov-de Haas oscillations have been studied in the quasi-two-dimensional organic superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br at different magnetic field orientations with respect to the conducting layers. At ambient pressure, the oscillation frequency spectrum reflects the Fermi surface topology predicted by band st...
The de Haas-van Alphen (dHvA) signal of the organic superconductor beta "-(BEDT-TTF)(2)SF5CH2CF2SO3 shows an inverse-sawtooth wave form which proves the existence of an ideal two-dimensional (2D) Fermi surface. The dHvA wave shape can almost perfectly be described by a 2D theory assuming a constant chemical potential. This either implies the existe...
The B-T phase diagram of alpha-(ET)(2)KHg(SCN)(4) has been studied under quasi-hydrostatic pressure by means of resistance measurements. Our proposed B-T phase diagrams at different pressures are qualitatively very similar to the theoretically predicted diagrams of an imperfectly nested charge-density-wave system. Furthermore, we observed indicatio...
The magnetic torque and Faraday force magnetisation of alpha-(BEDT-TTF)(2)KHg(SCN)(4) have been studied in magnetic fields up to 28 T and temperatures between 1.4 K and 15 K. The magnetic field was oriented nearly parallel to the highly conducting layers. The low temperature ground state is characterized by additional temperature dependent componen...
We present detailed studies of the B-T-P phase diagram of alpha-(BEDT-TTF)(2)KHg(SCN)(4) by means of magnetic torque and magnetoresistance measurements. The phase diagram for magnetic field oriented almost perpendicular to the highly conducting layers closely resembles that expected for a charge-density-wave (CDW) system with an imperfectly nested...
de Haas-van Alphen oscillations are observed in the alkaline-earth-metal subnitride NaBa3N. They are studied at various sample orientations with respect to the magnetic-field direction. A rich spectrum of quantum oscillation frequencies varying with the field orientation is found. The effective cyclotron masses of the carriers are found to depend o...
The quasi-two-dimensional organic superconductor beta"-(BEDT-TTF)2SF5CH2CF2SO3 (Tc approximately 4.4 K) shows very strong Shubnikov-de Haas (SdH) oscillations which are superimposed on a highly anomalous steady background magnetoresistance, Rb. Comparison with de Haas-van Alphen oscillations allows a reliable estimate of Rb which is crucial for the...
We report on Shubnikov}de Haas (SdH) and de Haas}van Alphen (dHvA) results for the highly two-dimensional (2D) organic superconductors -(ET) I (T "3.5 K) and -(ET) SF CH CF SO (T "4.4 K). The SdH oscillations of both materials show an apparent deviation from the well-understood 2D dHvA signal at low temperatures and high magnetic "elds. For -(ET) I...
In this paper, we report transport measurements of the interlayer magnetoresistance with field, H, parallel to the current, J, in the organic superconductor κ-(bis(ethylenedithio)-tetrathiafulvalene (ET))2I3. The isothermal magnetoresistance R(H) displays a peak as a function of field for 1>T/Tc≥0.4. At lower temperatures T/Tc<0.4, R(H) increases m...
We present systematic magnetic torque studies of the “magnetic field-temperature” phase diagram of the layered organic conductor
α-(BEDT-TTF)2KHg(SCN)4 at fields nearly perpendicular and nearly parallel to the highly conducting plane. The shape of the phase diagram is compared
to that predicted for a charge-density-wave system in a broad field rang...
de Haas-van Alphen measurements made on the organic metal β″-(BEDT-TTF)2SF5CH2CF2SO3 reveal the existence of an ideal two-dimensional (2D) Fermi surface, but rather than having the conventional sawtooth wave form that is normally observed in all other 2D electron gases, instead, an “inverse sawtooth” wave form is observed, which is to be expected w...
Resistivity and magnetoresistance have been measured on single crystals of the monophosphate tungsten bronzes (PO2)(4)(WO3)(2m) for m=5. The m = 5 compound exists in two structural varieties which lead to different resistivity and magnetoresistance properties. Shubnikov de Haas oscillations with large amplitude are observed in one of the variety. T...
De Haas-van Alphen and Shubnikov-de Haas oscillations in the organic superconductor kappa-(BEDT-TTF)2Cu[N(CN)2]Br have been studied at different orientations of the magnetic field with respect to the conducting layers. In addition to the previously reported magnetic breakdown frequency Fbeta(theta=0°)~=3790 T, a frequency of ~=530 T has been detect...
The interlayer magnetoresistance of the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br has been measured at ambient pressure and under pressure up to 12 kbar. Shubnikov-de Haas oscillations of two main frequencies, F − 3900 T and F − 150 T, corresponding to 100% and 3.5–4% of the Brillouin zone cross-section area, are observed in the pressure ran...
The conductors (PO2)4(WO3)2m show CDW type electronic instabilities. We report electrical properties of the m = 5 crystal variety made of a regular 5/5/5 stacking of WO3 layers. An anomaly at T~60K is observed in the electrical resistivity, Hall coefficient and thermoelectric power. The origin of the anomaly is discussed.
Detailed measurements of the interlayer magnetotransport of the organic superconductor κ-bis(ethylenedithio)tetrathiafulvalene2Cu[N(CN)2]Br have been carried out at ambient pressure as well as under quasihydrostatic pressure up to 12 kbar. Shubnikov–de Haas oscillations at frequencies ≈150, 300, and 3900 T have been observed at various pressures. T...
A new magneto-quantum oscillation (QO) frequency F0=13.2 T is observed in the normal conducting state of the strong two-dimensional (2D) organic superconductor κ-(BEDT-TTF)2I3. Such a frequency is neither predicted by band-structure calculations nor yet observed in Shubnikov–de Haas experiments on any κ-structured material of the BEDT-TTF family. A...
We have measured the temperature (T) dependence of the resistivity rho of the beta and K phases of (BEDT-TTF)2I3 from 300 K down to Tc ( approximately 1.3 K and approximately 4 K for the beta and kappa phases, respectively). Between 100 K and 20 K, rho varies as T2. Below 20 K, the resistivity falls below the T2 law. We calculate the resistivity du...
Resistivity and magnetoresistance have been measured on single crystals of the monophosphate tungsten bronzes (PO2)4(WO3)2m for m=5. The m = 5 compound exists in two structural varieties which lead to different resistivity and magnetoresistance properties. Shubnikov de Haas oscillations with large amplitude are observed in one of the variety. The o...
Spin-split de Haas-van Alphen oscillations in two-dimensional (2D) electron systems are studied experimentally and theoretically. It is shown that large second harmonic observed at low temperatures in the quasi-2D organic metal kappa-(ET)2I3 (ET≡BEDT-TTF) is due to the effect of spin-splitting close to its maximal value. The calculated shape and am...
We report on Shubnikov-de Haas and de Haas-van Alphen measurements of an organic metal based on the molecular donor bis(ethylenedioxy)-tetrathiavulvalene
(= BEDO-TTF) and the anion Cl- with H2O molecules. The observed single oscillation frequency perfectly follows the two-dimensional dependence with T. The Fermi-surface area of of the first Brillou...
Measurements of both the magnetization and magnetotransport of κ-(BEDT-TTF)2I3 (BEDT-TTF is bisethylenedithio-tetrathiafulvalene) in magnetic fields extending to 60 T at 0.4 K and 20 T at 35 mK are reported. Strong eddy currents observed in the magnetization are found to exhibit critical currentlike behavior. This might be connected with the breakd...
The electronic system of the organic superconductor κ-(BEDT-TTF)2I3 (BEDT-TTF = bis(ethylenedithiolo)tetrathiafulvalene) is identified as extremely two-dimensional (2D). The topology of the Fermi surface (FS) was investigated by means of Shubnikov-de Haas (SdH) as well as de Haas-van Alphen (dHvA) experiments focusing on the verification of the 2D...
Measurements of the magnetisation of kappa-(BEDT-TTF)2I3 in magnetic fields extending to 60 T are reported. An apparent loss of amplitude of the de Haas-van Alphen oscillations, or fall in the effective mass, can be attributed to the effects of an oscillatory chemical potential in a two-dimensional spin-split Fermi liquid. Meanwhile, the presence o...
The organic superconductor κ-(BEDT-TTF)2I3 was found to be an extreme two-dimensional (2D) electronic system. The topology of the Fermi surface (FS) was investigated by means of de Haas-van Alphen (dHvA) as well as Shubnikov-de Haas (SdH) experiments focusing on the verification of the 2D character of the system. This property specially takes effec...
We present dc-magnetization and ac-susceptibility measurements of the organic superconductors κ-(ET)2X with X = I3, Cu(NCS)2, and Cu[N(CN)2]Br. For all investigated materials the lower critical field perpendicular to the highly conducting planes, Bcl⊥, tends to zero already 0.5 K below Tc. This might be an indication for fluctuation effects of sing...
We report on a systematic study of the thermodynamic superconducting properties on high-quality crystals of the quasi-two-dimensional (quasi-2D) organic superconductor {kappa}-(BEDT-TTF){sub 2}I{sub 3}. Low-field magnetization measurements served to determine the lower critical field {ital B}{sub {ital c}1}. Just below {ital T}{sub {ital c}}=3.5K,...
κ-(BEDT-TTF)2I
3 is an extreme case of an electronically two-dimensional (2D) organic metal with a superconducting transition at around 4 K. In magnetic fields up to 27 T the field, angular and the temperature dependence of de Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) oscillation amplitudes were investigated. From the temperature dependenc...
κ-(BEDT-TTF)2I
3 is an extreme case of an electronically two-dimensional (2D) organic metal with a superconducting transition at around 4 K. In magnetic fields up to 27 T the field, angular and the temperature dependence of de Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) oscillation amplitudes were investigated. From the temperature dependenc...
The Fermi surfaces (FS) and effective masses of the organic superconductors (BEDO-TTF)2ReO4(H2O) (1) and κ-(BEDT-TTF)2I3 (2) were investigated by SdH- and dHvA-measurements in magnetic fields up to 27T in the temperature range from 0.5K to 4.2K. In 1 two small closed pockets (0.7% and 1.5% of the first Brillouin zone [FBZ] are observed correspondin...
κ-(BEDT-TTF)2I3 is an electronically extreme two-dimensional (2d) organic metal with a superconducting transition at around 4K. In magnetic fields above 12T the effective mass, as obtained from the temperature dependence of the amplitudes of Shubnikov-de Haas (SdH) oscillations, is magnetic field dependent mass, as long as the magnetic field is arr...
form only given. k-(BEDT-TTF)/sub 2/I/sub 3/ is an organic superconductor [1] with a T/sub c/ = 4 K. High quality single crystals of x-(BEDT-TTF)/sub 2/I/sub 3/ can be grown by electrochemical methods [2] and show already in magnetic fields from 5 to 12 Tesla giant quantum oscillations in Shubnikov de Haas (SdH)- and de Haas van Alphen (dHvA)- expe...
Investigations of the transport properties of single crystals and polycrystalline pressed samples of k-(BEDT-TTF)2I3 are presented. In contrast to polycrystalline pressed samples of k-(BEDT-TTF)2Cu(NCS)2 and k-(BEDT-TTF)2Cu[N(CN)2]Br those of k-(BEDT-TTF)2I3 show bulk superconductivity indicating that the loss of superconductivity in the first two...
We have measured the temperature (T) dependence of the resistivity rho of the beta and K phases of (BEDT-TTF)2I3 from 300 K down to Tc ( approximately 1.3 K and approximately 4 K for the beta and kappa phases, respectively). Between 100 K and 20 K, rho varies as T2. Below 20 K, the resistivity falls below the T2 law. We calculate the resistivity du...
Citations
... Br [32], the SdH frequency, the effective mass and T c are highly pressure dependent. The decrease of both T c and effective mass with pressure in the case of the 10 K superconductor κ-(BEDT- TTF) 2 Cu(NCS) 2 [33] and in α-(BEDT-TTF) 2 NH 4 Hg(SCN) 4 (T c ∼ 1 K) was also explicable using the pressure dependence of the interaction terms. ...
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... Indeed, the paramagnetic (Pauli) inhibition of the Peierls transition was shown theoretically [162,163] to be analogous to the suppression of the singlet Cooper pairing [164]. This behavior was confirmed experimentally for organic materials α-(ET) 2 MHg(SCN) 4 (M = K, Tl, Rb, etc.) [165][166][167][168], Per 2 [Au(mnt) 2 ], and Per 2 [Pt(mnt) 2 ] [169,170]. ...
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... In contrast to other θ-phase salts that undergo charge-ordering transitions into an insulating ground state [21,50,193], the dc resistivity of θ-(BEDT-TTF) 2 I 3 remains metallic down to T c = 3.6 K. The transition temperature can be raised above 5 K, when the specimens are tempered at 70 • C [430]. Quantum oscillations prove the presence of a Fermi surface with two-dimensional orbits and one-dimensional trajectories [430][431][432][433]. ...
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... While not predicted by band structure calculations, a small MB gap between the open sheets and cylindrical Fermi surface has also been found in SdH experiments on several other κ-type salts of BETS and BEDT-TTF with a center-symmetric layer structure [32][33][34][35][36][37][38][39]. One can consider a weak, 1 meV, spin-orbit interaction as a possible source of the gap [40]. ...
... The large orbit ? is then a consequence of mag-netic breakdown (MB) through the small gap between the different parts of the Fermi surface. Similar evidence of the MB effect were found on several well known ?(BEDT-TTF ) 2 X salts [24][25][26][27]. The SdH spectrum in Fig. 2differs from that reported earlier for this compound at similar pressures [22]. ...
... The transition temperature can be raised above 5 K, when the specimens are tempered at 70 • C [430]. Quantum oscillations prove the presence of a Fermi surface with two-dimensional orbits and one-dimensional trajectories [430][431][432][433]. The presence of a Fermi-liquid state is also seen from a quadratic temperature increase in the resistivity observed at low temperatures. ...
... The large orbit β is then a consequence of mag-netic breakdown (MB) through the small gap between the different parts of the Fermi surface. Similar evidence of the MB effect were found on several well known κ-(BEDT-TTF) 2 X salts [24][25][26][27]. ...
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... The Dingle temperature ranges from 0.24 to 0.52 K. 16) In such a highly 2D case, a lot of discussions on the QO waveshape have been made. [17][18][19][20][21][22] The QOs in the resistance 15,16,23) and magnetic torque 17) for 00 -SF 5 are almost sinusoidal or a slightly inversed sawtooth, which are discussed on the assumption of the fixed chemical potential. 18) By contrast, we observe strongly deformed waveshape of the QO in the MCE associated with large hysteresis at high fields. ...
... The relations ξ = av F /k B T c (k B : Boltzmann constant; v F : Fermi velocity; a: constant) and v F ∝ 1/m * jointly suggest that ξ is inversely proportional to m * T c , which varies with pressure. Referring to the pressure dependences of T c shown in Fig. 1(c) and of the β-orbit (surrounding the whole Fermi surface) mass m * , determined by the Shubnikov-de Haas oscillations [48], the pressure dependence of (1 + ξ/l ) is calculated as shown in Fig. 5. Figure 6 ...
... Br [14], where in dHvA experiments a node appears at 23.5 T, while no beating in SdH measurements in the field range between 16 and 28 T is observed. Except for the different positions of the beating nodes, the dHvA and SdH experiments on (BEDT-TTF) 4 [ the LK theory (see [15, 16] and references therein). ...
