Journal of Physics: Conference Series High-pressure specific heat technique to uncover novel states of quantum matter

Abstract

AC-specific heat measurements remain as the foremost thermodynamic experimental method to underpin phase transitions in tiny samples. However, its performance under combined extreme conditions of high-pressure, very low temperature and intense magnetic fields needs to be broadly extended for investigation of quantum phase transition in strongly correlated electron systems. In this communication, we discuss the determination of specific heat on the quantum paramagnetic—insulator SrCu2(BO3)2 by applying the AC-specific heat technique under extreme conditions. In order to apply this technique to insulating samples we sputtered a metallic thin film-heater and attached thermometer onto sample. Besides that, we performed full frequency scans with the aim to get quantitative specific heat data. Our results show that we can determine the sample heat capacity within 5% of accuracy respect to an adiabatic technique. This allows to uncover low energy scales that characterize the ground state of quantum spin entanglement in SrCu2(BO3)2.

A quantum magnetic analogue to the critical point of water

“…Extended Data Fig. 1c, d demonstrates the correct determination of f C = 1.5 Hz at P = 18.2 kbar, whose measurement at fixed f C (a 'T scan') reproduces the same result as obtained from our f-scan analysis 29 .…”

“…Our methodology allowed us to determine the heat capacity within an accuracy of 5% with respect to an adiabatic technique. Further details concerning all aspects of the procedures of our a.c. calorimetry measurements may be found in previous work 29 .…”

“…Our a.c. calorimetry set-up was sputtered onto the sample slab to guarantee good thermal contact of the sample, heater and thermometer 29 . It consisted of two separate Pt films, one used as the heater and the other used to improve the thermal contact between sample and thermometer, as shown in Extended Data Fig.…”

“…These advantages include a more precise determination of the corrections for unwanted heat losses throughout the sample, a more precise separation of additional P-dependent contributions and the ability to achieve an optimal thermal equilibrium inside the sample (within the resolution of the thermocouple). Thus, our 'f-scan' analysis 29 allows an accurate determination of the working frequency (f C ) at which to maximize C(P, H, T) at each pressure. Extended Data Fig.…”

“…To investigate the possibility of a critical point in SrCu 2 (BO 3 ) 2 , we perform high-precision measurements of the specific heat using an a.c. calorimetry technique 29 . Large single crystals of SrCu 2 (BO 3 ) 2 were grown by a floating-zone method (Methods).…”