Mott transition, compressibility divergence, and the P-T phase diagram of layered organic superconductors: an ultrasonic investigation.

The phase diagram of the organic superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl has been investigated by ultrasonic velocity measurements under helium gas pressure. Different phase transitions were identified through several elastic anomalies characterized from isobaric and isothermal sweeps. Our data reveal two crossover lines that end on the critical point terminating the first-order Mott transition line. When the critical point is approached along these lines, we observe a dramatic anomaly of the sound velocity which is consistent with a diverging compressibility of the electronic degrees of freedom.

[1]  G. Kotliar,et al.  Compressibility divergence and the finite temperature Mott transition. , 2002, Physical review letters.

[2]  M. Imada,et al.  Filling-Control Metal-Insulator Transition in the Hubbard Model Studied by the Operator Projection Method , 2001, cond-mat/0107291.

[3]  R. McKenzie,et al.  Phonon anomalies due to strong-electronic correlations in layered organic metals , 2000, cond-mat/0007173.

[4]  Y. Endoh,et al.  Magnetic Phase Diagram and Metal-Insulator Transition of NiS2 xSex , 2000, cond-mat/0006185.

[5]  P. Batail,et al.  Mott transition, antiferromagnetism, and unconventional superconductivity in layered organic superconductors. , 2000, Physical review letters.

[6]  M. Poirier,et al.  Elastic Study of Antiferromagnetic Fluctuations in the Layered Organic Superconductors kappa-(BEDT-TTF)_2X , 1999, cond-mat/9911057.

[7]  Masatoshi Imada,et al.  Metal-insulator transitions , 1998 .

[8]  R. McKenzie.  Similarities Between Organic and Cuprate Superconductors , 1997, Science.

[9]  K. Kanoda.  Electron correlation, metal-insulator transition and superconductivity in quasi-2D organic systems, (ET)2X , 1997 .

[10]  Hiroshi Ito,et al.  Metal-Nonmetal Transition and Superconductivity Localization in the Two-Dimensional Conductor κ-(BEDT-TTF) 2Cu[N(CN) 2]Cl under Pressure , 1996 .

[11]  W. Krauth,et al.  Dynamical mean-field theory of strongly correlated fermion systems and the limit of infinite dimensions , 1996 .

[12]  Poirier,et al.  Doping effects on the magnetic phase diagram of the spin-Peierls system CuGe1-xSixO3. , 1995, Physical Review B (Condensed Matter).

[13]  Kawamoto,et al.  13C NMR Study of Layered Organic Superconductors Based on BEDT-TTF Molecules. , 1995, Physical review letters.

[14]  C. Lenoir,et al.  13C NMR Study of a Quasi-Two-Dimensional Organic Superconductor ?-(ET)2Cu[N(CN)2]Br , 1994 .

[15]  Andrés,et al.  Superconducting Meissner effect under hydrostatic pressure in the ambient-pressure semiconductor kappa -(BEDT-TTF)2Cu(N(CN)2)Cl, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene. , 1993, Physical review. B, Condensed matter.

[16]  Poirier,et al.  Ultrasonic study of the quasi-one-dimensional spin fluctuations in CsNiCl3 in the presence of a magnetic field. , 1992, Physical Review B (Condensed Matter).

[17]  E. Yagubskii,et al.  Hydrostatic pressure effect on Tc and resistance anomaly in normal state of κ-(BEDT-TTF)2CuN(CN)2Br , 1991 .

[18]  D. L. Overmyer,et al.  New κ-phase materials, κ-(ET)2Cu[N(CN)2]X.X=Cl, Br and I. The synthesis, structure and superconductivity above 11 K in the Cl (Tc = 12.8 K, 0.3 kbar) and Br(Tc = 11.6 K) salts , 1991 .

[19]  J. P. Remeika,et al.  Electronic Specific Heat of Metallic Ti-Doped V 2 O 3 , 1971 .