Magneto-thermopower of a chaotic, ballistic quantum dot

We present measurements of the magneto-thermopower fluctuations of a gate-d efined, chaotic quantum dot in a (Al,Ga)As-semiconductor heterostructure. C urrent-heating techniques were employed to build up the necessary temperatu re difference across the quantum dot for the thermopower measurement. A sta tistical ensemble is generated by registering the magnetic-field and gate-v oltage dependence for a number of slightly different dot sizes. The experim ental results are in good agreement with the predicted non-gaussian distrib ution of the Random Matrix Theory. To our knowledge these are the first tra nsport experiments that directly yield the non-gaussian distribution which are an unambiguous sign for the occurence of chaos. (C) 1998 Elsevier Scien ce B.V. All rights reserved.